Abstract
Lung cancer is among the most common cancers worldwide and is the leading cause of cancer death in both men and women. For patients with early stage (American Joint Committee on Cancer T1-2, N0) non–small-cell lung cancer, the current standard of care is lobectomy with systematic lymph node evaluation. Unfortunately, patients with lung cancer often have medical comorbities, which may preclude the option of surgical resection. In such cases, a number of minimally invasive to noninvasive treatment options have gained popularity in the treatment of these high-risk patients. These modalities provide significant advantages, including patient convenience, treatment in an outpatient setting, and acceptable toxicities, including reduced impact on lung function and a modest risk of postprocedure chest wall pain. We provide a comprehensive review of the literature, including reported outcomes, complications, and limitations of sublobar resection with or without intraoperative brachytherapy, radiofrequency ablation, microwave ablation, percutaneous cryoablation, photodynamic therapy, and stereotactic body radiotherapy.
Keywords
Introduction
Lung cancer is among the most common cancers worldwide and is the leading cause of cancer death in both men and women.
1
In the United States alone, It is estimated that 226,150 cases of lung and bronchus cancer were diagnosed in 2012, and the disease accounted for 160,340 deaths.2
Non–small-cell lung cancer (NSCLC) accounts for more than 85% of all lung cancer cases, with approximately 15% to 20% of patients presenting with early stage (T1-2, N0) disease. Lobectomy with systematic lymph node evaluation is considered the optimal treatment in patients with early stage NSCLC. However, no randomized clinical data directly compare surgery alone to radiation alone or ablative techniques in the management of patients whose disease is amenable to surgery.Surveillance, Epidemiology, and End Results (SEER) Program. Research data, 1975-2007. National Cancer Institute, DCCPS, Surveillance Research Program, Cancer Statistics Branch. Available at: http://www.seer.cancer.gov. Accessed March 1, 2015.
3
The acceptance of lobectomy as the optimal therapy is based on historical data, registry studies, and retrospective series, which consistently demonstrate 5-year overall survival (OS) rates ranging from 60% to 80% and 40% to 60% for stage I and II NSCLC, respectively.4
, 5
, 6
For patients unable to tolerate lobectomy, alternative treatment options include best supportive care, limited resection (wedge resection or segmentectomy), and external beam radiotherapy. Studies demonstrate that limited resections generally result in 5-year survival and recurrence rates of 59% and 50%, respectively.
7
Definitive external beam radiotherapy delivered in standard fractionation (45 to 66 Gy in 1.8 to 2 Gy per fraction) results in local relapse in 55% to 70% of patients, with a reported median survival of > 30 months and 5-year survival rates of up to 30%.8
These consistently inferior results compared to lobectomy have led to new therapeutic approaches in the management of such inoperable/high-risk patients as well as those who decline operative intervention.Here we provide a review of the primary treatment options available for early stage NSCLC deemed to be high-risk or medically inoperable. Such treatments include limited resection with and without intraoperative brachytherapy, radiofrequency ablation (RFA), microwave ablation (MWA), percutaneous cryoablation (PCT), photodynamic therapy (PDT), and stereotactic body radiotherapy (SBRT).
Review Methods
A review of the NSCLC treatment literature was conducted. A comprehensive systematic literature search included the Cochrane Collaboration Library electronic database, PubMed, RTOG.org, and ClinicalTrials.gov, using the following terms and keywords: NSCLC, early stage, surgery, lobectomy, limited resection, wedge resection, segmentectomy, EBRT, SBRT, RFA, MWA, cryoablation, PCT, and brachytherapy, and a combination of these terms. Studies were limited to those reported in the English language and involving human subjects. Review articles and original data from the last 30 years were reviewed independently.
Surgery
The standard treatment for operable early stage NSCLC is lobectomy with systematic lymph node dissection.
9
However, there are currently no universally accepted definitions for medical operability.10
, 11
Factors including patient age, cardiopulmonary reserve, presence and extent of medical comorbidities, and overall performance status are included in the preoperative assessment.12
In addition to the determination of operability, accurate nodal assessment is considered critical as a result of the influence of nodal staging on both the primary and adjuvant treatment options for early stage disease. One study of 100 NSCLC patients with ≤ 1 cm tumors demonstrated a 5% incidence of node involvement, implying that even in small tumors, nodal assessment cannot be ignored.13
Methods for analysis of nodal involvement include computed tomography (CT) and/or positron emission tomography, endobronchial ultrasound, transbronchial needle biopsy, and mediastinoscopy.Although lobectomy is considered the reference standard, patients with severe chronic obstructive pulmonary disease (COPD) and poor lung function are at a substantially greater risk of postoperative complications. The risk of complications for healthy individuals with normal lung function undergoing resection is approximately 2% to 5%, while those with preexisting lung disease have up to a 50% risk. Thus, preoperative studies including complete pulmonary function testing (spirometry) to quantify baseline pulmonary function and reserve is generally recommended.
11
If the forced expiratory volume in 1 second (FEV1) is > 2 L or > 80% of its predicted value, resection can be attempted with an acceptable risk of complications.10
Patients with an FEV1 < 40% or carbon monoxide diffusing capacity (DLCO) < 40% are at increased risk of perioperative morbidity and mortality. Some investigators recommend nonoperative management if the product of the percentage of predicted postoperative FEV1 and DLCO combined is < 1650, if the percentage of predicted postoperative FEV1 is < 30%, or if the maximum oxygen uptake is less than 10 mL/kg/min.9
In subjects with medical comorbidities, a more limited resection may be offered to reduce the impact of lobectomy on lung function and maintain the patient's quality of life. One report suggested that over 20% of patients with stage I or II NSCLC cannot undergo lobectomy as a result of comorbid health factors.
14
Limited resections are generally offered to patients with poor baseline cardiopulmonary function with tumors < 2 cm in diameter. In patients with small, node-negative tumors excised to negative margins, limited resection may result in local control (LC), OS, and cause-specific survival (CSS) comparable to lobectomy.6
, 15
, 16
, 17
, 18
In 1995, the Lung Cancer Study Group published the first randomized, prospective study comparing limited resection to lobectomy in the definitive management of T1N0 lung cancer.
5
, 19
The study enrolled 247 patients with 125 randomized to lobectomy and 122 to a limited resection (82 segmentectomies and 40 wedge resections). With a median follow-up of 60 months, LC rates were 93.6% for the lobectomy group compared to 83% in those treated with limited resection (P = .008). Although the OS was statistically comparable at 69.6% and 60.7% for lobectomy versus limited resection (P = .088), the local recurrence rate (0.020 to 0.060 per patient per year, P = .008) for the patients undergoing limited resection was tripled compared to lobectomy. The high rate of local recurrence in the limited resection cohort resulted in critical evaluation regarding the definitive role of sublobar resection.A Surveillance, Epidemiology, and End Results (SEER) registry study evaluated patients older than 65 years of age with stage IA lung cancer (tumors ≤ 2 cm without clinically or radiographically apparent lymph nodes) treated with either lobectomy or limited resection. This analysis found no significant difference in OS between the treatment groups, but there was evidence of an increased risk for lung cancer death after limited resection in patients with tumors measuring 2 to 3 cm.
20
Subsequently, Warren and Faber17
evaluated the outcomes of stage I NSCLC patients with poor cardiopulmonary reserve. The authors reported a higher risk of locoregional recurrence in patients undergoing segmentectomy versus those who had a lobectomy (22.7% and 4.9%, respectively), although 5-year OS was equivalent.Several other retrospective studies have demonstrated that lobectomy and limited resection yield equivalent survival for tumors ≤ 2 cm. For example, Okada and colleagues
21
reported 5-year survival rates of 87.1% and 87.8%, respectively, for T1N0 tumors of < 2 cm and treated with extended segmentectomy (and lymph node dissection) versus lobectomy. Koike and colleagues22
reported 5-year survival rates of 89.1% and 90.1%, respectively, for limited resection versus lobectomy for peripheral T1N0 tumors. Kodama and colleagues23
conducted a retrospective analysis of patients with T1N0 lung cancer that again found no significant difference in 5-year survival in the lobectomy group (88%) compared to the limited resection group (93%). Kates and colleagues24
queried the SEER database for stage IA tumors < 1 cm and found no significant difference in survival in 1402 patients who underwent lobectomy compared to 688 patients treated with limited resection.Age at diagnosis is often an important determinant of outcomes in NSCLC, in which patients present at an average age of 67 years and approximately 45% of patients are 70 years or older at the time of diagnosis.
25
In fact, the postoperative mortality rate is 9.4% for octogenarians and 1.7% for patients under the age of 60 years.15
A SEER database study looking specifically at elderly patients with stage I and II NSCLC was published by Mery and colleagues.26
The study identified 9875 patients treated with lobectomy and 1403 treated with limited resection with evidence to suggest a decrease in the utilization of lobectomy with an associated increase in the number of limited resections as patient age increased (P < .0001). Survival decreased with increasing age, with median survival times of 71, 47, and 28 months for patients < 65, 65 to 74, and ≥ 75 years of age, respectively (P < .0001). In this analysis, lobectomy conferred an OS benefit over limited resection in both the < 65 (P = .03) and 65 to 74 (P = .0009) cohorts. However, for the group ≥ 75 years of age, there was no difference in OS (P = .47), with a loss of the statistical difference in long-term survival (> 25 months) in patients > 71 years of age in post hoc analysis.Keenan and colleagues
27
investigated whether segmental resection offered an advantage in preservation of lung function compared to lobectomy. In a cohort of 201 patients with tumors less than 3 cm, of whom 147 underwent lobectomy and 54 underwent segmentectomy, postoperative pulmonary function to include FEV1 and forced vital capacity were better preserved in the segmentectomy group at 1 year of follow-up. LC rates at 30 months (92.5% vs. 88.9%; P = .22), 4-year actuarial survival (67% vs. 62%; P = −.406), and 4-year CSS (82% vs. 74%; P = .71) were comparable for lobectomy versus segmentectomy, respectively. In the absence of a significant difference in LC or OS, the authors concluded that segmentectomy could be offered to patients with small (< 3 cm), node-negative NSCLC with improved preservation of pulmonary function. These results were supported by Okada and colleagues,28
who reported on a nonrandomized study that segmentectomy in early stage IA NSCLC produced outcomes comparable to lobectomy in a group of 567 patients with 305 patients treated with lobectomy and 262 undergoing limited resection (230 segmentectomy, 32 wedge resection). LC at 71 months (93.1% vs. 95.1%; P = .3524), 5-year OS (89.1% vs. 89.6%; P = −.106), and disease-free survival (DFS) between the 2 groups were not significantly different in patients resected to a negative margin (≥ 2 cm) with a negative nodal assessment.In contrast, several studies have described significant differences in OS between lobectomy and limited resection. El-Sherif and colleagues
29
compared the outcomes of sublobar resection to lobectomy in 784 patients with peripheral tumors less than 2 cm confined within anatomic segmental boundaries. Lobectomy was performed in 577 patients and limited resection (consisting of either segmentectomy or wedge resection) in the remaining 207 patients. The median tumor size for the lobectomy and limited resection groups were 2.8 versus 1.8 cm. With a median follow-up of 31 months, LC for the lobectomy group was 95.8% compared to 92.8% for the limited resection group. The 5-year OS for the lobectomy group was 54% compared to 40% for the limited resection group (P = .0038); however, no significant difference was identified between the 2 groups in regard to DFS. The authors suggested that the improvement in OS was due to other variables, given the similar DFS and evidence to support increased use of sublobar resection in patients with competing comorbidities and increased risk of death. Sienel and colleagues30
evaluated outcomes in high-risk T1N0 NSCLC patients treated with lobectomy compared to segmentectomy. The local recurrence rate was 16% in patients with segmentectomy compared to 5% for lobectomy. The CSS was 68% for segmentectomy and 83% for lobectomy (P = .01). Similarly, Kraev and colleagues31
compared 215 patients who underwent lobectomy to 74 patients treated with wedge resection for stage I NSCLC. In the entire cohort, there was a trend toward improved survival with lobectomy (5.8 vs. 4.1 years), while in patient with ≤ 3 cm tumors, there was a statistically significant improvement in survival (P = .029).Further retrospective reports have described mixed nonsignificant differences in survival between lobectomy and limited resection for patients with poor cardiopulmonary function. Errett and colleagues
16
reported a 6-year survival of 69% versus 75% in favor of lobectomy, while Pastorino and colleagues32
found the 5-year survival for limited resection in high-risk patients was actually slightly better, at 55% compared to 49% in the lobectomy group. Similarly, Read and colleagues33
reported a higher 5-year survival, 84% and 74%, in 244 patients with T1N0 tumors treated with limited resection (n = 113) versus lobectomy (n = 131), respectively.Martin-Ucar and colleagues
34
reported on a case-matched analysis of segmentectomy versus lobectomy in high-risk (FEV1 < 40%) stage I NSCLC patients. Seventeen patients underwent segmentectomy and 17 underwent lobectomy. The study found that there was no significant difference in survival, local recurrence, or DFS between the 2 groups. There was an improvement in FEV1 (P = .02) and quality of life after segmentectomy. A similar study of T1N0 NSCLC patients treated with either lobectomy or limited resection found that those treated with limited resection were older and had more comorbidities than the lobectomy cohort; however, the 5-year survival of the 2 groups (64% for lobectomy and 66.7% for limited resection) was not statistically different.35
Landreneau and colleagues
6
retrospectively evaluated 2 forms of limited resection–wedge resection via video-assisted thoracic surgery (VATS) or open wedge resection and compared these techniques to lobectomy. Of 219 patients, 117 underwent lobectomy and 102 underwent wedge resection (42 via open wedge resection and 60 via VATS). The median tumor size by procedure was 2, 1.7, and 1.7 cm for lobectomy, VATS wedge, and open wedge resection, respectively. With a median follow-up of 26 months, the LC by procedure was 91%, 84%, and 76% with postoperative complication rates of 31%, 16%, and 28%, respectively. One-year survival for the lobectomy group was 91% compared to 94% for the combined wedge resection group. Five-year survival was significantly better in the lobectomy group compared to the combined wedge resection group (70% vs. 61.5%, P = .02). A more recent study compared open wedge versus VATS resection in regard to outcomes and costs and demonstrated that VATS had several advantages, including a reduction in expense, a decrease in adverse events, and decreased time spent in the hospital.36
Schuchert and colleagues
37
reviewed 428 patients undergoing lobectomy or segmentectomy to study the effect of margin status on outcome. Two hundred forty-six patients underwent lobectomy and 182 underwent segmentectomy. The average tumor size was 3.1 and 2.3 cm for the lobectomy and the segmentectomy group, respectively. When analyzed collectively, the mean margin among patients with recurrence was 12.8 versus 18.6 mm in patients without recurrence. Margin/tumor diameter ratios exceeding 1 were associated with a significant reduction in recurrence rates compared to ratios of less than 1 (6.2% vs. 25%, P = .001). Although follow-up varied between the 2 groups, outcomes were comparable. The LC rate was 95.2% versus 92.3%, and the 4-year OS estimates were 80% versus 83% for lobectomy versus segmentectomy, respectively; there was no significant difference in DFS between the groups.Table 1 provides a summary of the studies that have reported on sublobar resection for lung cancer. These demonstrate that limited resection may allow for improved preservation of pulmonary function and similar OS compared to lobectomy at the expense of diminished LC. Importantly, limited resections also carry risks inherent to thoracic surgery, including perioperative complications such as rial fibrillation, prolonged air leaks, infection, and death.
36
Thus, lobectomy remains the standard treatment of early stage lung cancer, with limited resection reserved as an option for high-risk patients.Table 1Studies Including Sublobar Resection
| Study (Year) | No. Patients (No. Tumors) | Disease Stage | Tumor Location | Tumor Size | Follow-Up | LC Rate | 1 Year Survival | 2 Year Survival | OS | CSS | Complications | Lung Function Criteria |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Lung Cancer Study Group (1994, 1995) 5 | 247 (lobectomy 125, limited resection 122 [segmentectomy 85, wedge 40]) | T1N0 | Peripheral | ≤3 cm | Mean 60 mo, minimum 36 mo (53 mo minimum for lobectomy, 54 mo for limited resection) | Lobectomy 93.6%, limited resection 83% (P = .008) | Lobectomy 95% (Fernando 2005 [review]) | Lobectomy 80% (Fernando 2005 [review]) | Lobectomy 69.6%, limited resection 60.7% (P = .088) | NA | NA | Preoperative FEV1 ≥50% |
| Landreneau (1997) 6 | 219 (wedge 102, lobectomy 117) | Stage I NSCLC | Peripheral | Median wedge 1.8 cm, lobectomy 2 cm | Mean wedge 27 mo, lobectomy 26 mo | Wedge 81%, lobectomy 91% | Wedge 94%, lobectomy 91% | Wedge ∼72%, lobectomy ∼87% | 5 years: wedge 61.5%, lobectomy, 70% (P = .02) | NA | Respiratory failure, empyema, wound infection, air leak, myocardial infarction, arrhythmias, sepsis | COPD 66.5%, 14%; FEV1 65%, 88%; DLCO 62%, 81% |
| Keenan (2004) 27 | 201 (lobectomy 147, segmentectomy 54) | Stage I; NSCLC; lobectomy 126 IA, 21 IB; segmentectomy 47 IA, 7 IB | NA | Lobectomy NA; segmentectomy 55.5% ≤2 cm, 44.4% 2-3 cm | Lobectomy 32.9 ± 1.6 mo, segmentectomy 27.4 ± 2.2 mo (NS) | Lobectomy 92.5%, segmentectomy 88.9% (P = .22) | Lobectomy 78%, segmentectomy 81.5%; active surveillance: lobectomy 95%, segmentectomy 92% | NA | 4 years: active surveillance lobectomy 67%, segmentectomy 62% (P = .406) | 4 years: lobectomy 82%, segmentectomy 74% (P = .71) | Operative mortality: lobectomy 4.8%, segmentectomy 5.6% | FEV1 55.3% |
| Okada (2006) 28 | 567 (sublobectomy 305 [230 segmentectomy, 32 wedge], lobectomy 262) | Sublobectomy, lobectomy IA (266, 217), IB (7, 10), IIA (10, 12), IIB (2, 2), IIIA (14, 15), IIIB (6, 6) | Peripheral | ≤2 cm; sublobectomy mean 1.57, range 5-2 cm; lobectomy mean 1.62 cm, range 0.8-2 cm | Sublobectomy median 72 mo, range 29-155 mo; lobectomy median 71 mo, range 22-158 mo | Sublobectomy 95.1%, lobectomy 93.1% (NS) | Sublobectomy 98% (Fernando 2010 [review]) | Sublobectomy 96% (Fernando 2010 [review]) | 5 years: sublobectomy89.6% (NS between types; P = .4335); lobectomy 89.1% (NS) | DFS, figure 2, NS (P = .2778); sublobectomy (NS between types; P = .8667); DFS at 5 years, sublobectomy 85.9%; lobectomy 83.4% | Sublobectomy 6.6%, lobectomy 7.3% (P = .7429) | FEV1 (wedge (n = 18), segmentectomy (n = 168), lobectomy (n = 168); preop 2.29 ± 0.59, 2.32 ± 0.64, 2.32 ± 0.58; postop: 2.21 ± 0.84, 2.10 ± 0.62, 1.93 ± 0.58 |
| El-Sherif (2006) 29 | 784 sublobectomy (wedge 122, segmentectomy 85), SLR 207, lobectomy 577 | Stage I NSCLC: sublobectomy 161 IA, 46 IB; lobectomy 288 IA, 289 IB | NA | Sublobectomy median 1.8 cm, lobectomy median 2.8 cm | Median 31 mo | Locoregional: sublobectomy 86%, lobectomy 92% | NA | NA | 5 years: sublobectomy 40%, lobectomy 54% (P = .0038) | DFS: NS | Perioperative mortality: sublobectomy 1.4%, lobectomy 2.6% | NA |
| Sienel (2007) 30 | 199 (segmentectomy 49, lobectomy 150) | Stage IA NSCLC | NA | 2.03 ± 0.96 cm, segmentectomy 1.8 ± 0.75 cm, lobectomy 2.8 ± 1.04 cm | Median 54 mo | Segmentectomy 84%, lobectomy 95% (P = .005) | NA | NA | 5 years: 79%; CRS: segmentectomy 67%, lobectomy 83% (P = .01) | CRS: significantly different; segmentectomy 67%, lobectomy 83% (P = .01) | NA | Median FEV1: segmentectomy 45%, lobectomy 44% |
| Schuchert (2007) 37 | 428 (segmentectomy 182, lobectomy 246) | Segmentectomy IA 109, IB 73; lobectomy IA 114, IB 132 | NA | Segmentectomy 2.3 (0.2-7.0) cm, lobectomy 3.1 (0.5-11.2) cm | Segmentectomy mean 18.1 mo, lobectomy 28.5 mo | Segmentectomy 92.3%, lobectomy 95.1% (P > .05) | Segmentectomy ∼98%, lobectomy ∼96% | Segmentectomy ∼88%, lobectomy ∼90% | 4 years: segmentectomy ∼83%, lobectomy ∼80% (NS) | DFS: figure 1A; no significant difference | Segmentectomy 32.4%; overall, 13.2% major; lobectomy 33.7%; overall, 13.8 major; AF 9.2% | FEV1: segmentectomy 1.7 (70%), lobectomy 1.81 (74%); DLCO: segmentectomy 13.9 (66%), lobectomy 15.1 (69%) |
| Wisnivesky (2010) 20 | 1165 (lobectomy 969, limited resection 196) | Stage I NSCLC | NA | ≤2 cm: lobectomy 1.59 ± 0.37 cm, limited resection 1.49 ± 0.41 cm | 59 mo | NA | NA | NA | HR 1.09 (NS) | HR 1.39 (NS) | NA | NA |
| Zemylak (2010) 88 | 64 (SLR 25, RFA 12, PCT 27) | Stage I NSCLC | NA | Not defined | 33 mo | SLR 88%, RFA 67%, PCT 89% (P > .05) | NA | NA | 3 years OS: SLR 87.1%, RFA 87.5%, PCT 77% | 3 year CSS: SLR 90.6%, RFA 87.5%, PCT 90.2% | Pneumothorax, hemoptysis | Major criteria: FEV1 ≤50% predicted, DLCO ≤50% predicted; minor criteria: FEV1 51%-50%, DLCO 51%-60%; pulmonary hypertension |
Abbreviations: SLR = sublobar resection; COPD = chronic obstructive pulmonary disease; CRS = cytoreductive surgery; CSS = cause-specific survival; DFS = disease-free survival; DLCO = carbon monoxide diffusing capacity; FEV1 = forced expiratory volume in 1 second; HR = hazard ratio; LC = local control; NA = not applicable; NS = not statistically significant; NSCLC = non–small-cell lung cancer; OS = overall survival; PCT = percutaneous cryoablation; RFA = radiofrequency ablation.
a Analysis based on sublobectomy, not wedge/segmentectomy.
Intraoperative Brachytherapy After Limited Resection
Intraoperative brachytherapy has the potential to improve LC after limited resection of early stage NSCLC.
38
, 39
, 40
Such low-dose-rate brachytherapy techniques permit delivery of radiation doses to the high-risk surgical bed over a period of weeks to months with the additional advantages of predictable, focal, and highly conformal dose distribution with decreased adverse effects resulting from a reduction in the irradiated normal tissue volume.41
An early report described 14 patients who received brachytherapy after wedge resection of peripheral lung cancers.
42
The patients had an average FEV1 of 23% and tolerated the intervention well, with no reported cases of radiation pneumonitis. Chen and colleagues43
evaluated administration of iodine-125 (I-125) mesh brachytherapy in high-risk stage I NSCLC patients. Twenty-three patients underwent VATS and intraoperative brachytherapy to a total dose of 100 to 120 Gy to the staple line and tumor bed plus a 1 cm margin. Postoperative pulmonary function testing performed at 3 months revealed no significant changes in FEV1 from baseline.Voynov and colleagues
44
assessed the delivery of 100 to 120 Gy via I-125 Vicryl mesh to the staple line plus a 2 cm margin in 110 patients with stage IA and IB NSCLC. The 5-year LC was 90%, locoregional control was 61%, and OS was 18%, with most deaths reported as not cancer related. Lee and colleagues45
evaluated 33 patients with early stage NSCLC (35 primary tumors) who were not candidates for lobectomy or pneumonectomy treated with limited resection and brachytherapy seed implantation along the resection margin. The 5-year survival was 47% for all patients, while those with T1N0 lesions had a 5-year survival of 67%; those with T2N0 lesions demonstrated a 5-year survival of 39%, with 2 local relapses and 6 patients experiencing regional recurrence.Santos and colleagues
46
analyzed data for high-risk NSCLC patients with poor cardiopulmonary reserve treated with surgical resection with or without permanent intraoperative I-125 brachytherapy prescribed to a dose of 100 to 120 Gy. Regional and distant failure rates as well as OS were not significantly improved with the addition of brachytherapy; however, the rate of local recurrence was decreased (2% vs. 18.6%, P = .001). A similar finding was reported by Fernando and colleagues,47
who evaluated 291 high-risk patients with stage IA NSCLC, 60 of whom received brachytherapy in conjunction with a sublobar resection. In these patients, the addition of brachytherapy associated with a decreased local recurrence rate (17.2% vs. 3.3%, P = .012).Birdas and colleagues
48
looked at 167 patients with high-risk stage IB NSCLC, of whom 126 underwent lobectomy and 41 underwent sublobar resection with brachytherapy. The average tumor size was not equivalent between the 2 groups, reported as 4.3 cm for the lobectomy group and 3.3 cm for those in the brachytherapy group (P = .007). The local recurrence rates (4.8%) were identical in both groups, and there was no significant difference in 4-year DFS (43% and 42.8%). Pulmonary complications were increased in those treated with sublobar resection when brachytherapy was added (24.4% vs. 16.6%).Parashar and colleagues
38
retrospectively reviewed 47 patients who underwent wedge resection and intraoperative brachytherapy versus SBRT alone for treatment of a single malignant lung nodule. Twenty-two patients were treated with brachytherapy after resection and 25 patients with SBRT alone. LC, distant metastasis rates, survival, and toxicity were all comparable between the 2 cohorts, with the caveat that there was a significant difference in age between the patients in each group (66.6 years in the brachytherapy group and 75.9 years in the SBRT group, P = .04).Martinez-Monge and colleagues
49
provided preliminary data with brachytherapy alone in 7 patients who were deemed to have medically inoperable early stage NSCLC. Brachytherapy was performed via CT-guided placement of palladium-103 or I-125 sources in tumors with an average volume of 11.5 cm3 resulted in no local or regional failure with a median follow-up of 13 months. Two patients died from stroke and liver failure, while one developed a new primary lung tumor at 8 months in the contralateral lung.The American College of Surgeons Oncology Group (ACOSOG) Z4032 study was a prospective comparison of sublobar resection with or without brachytherapy for high-risk operable patients (FEV1 < 50%) with NSCLC (< 3 cm). The study enrolled 224 patients with 115 patients randomized to surgery and 109 patients to surgery combined with brachytherapy. An initial presentation of the data at the American Society of Clinical Oncology 2013 annual meeting suggested that local recurrence and OS rates at 3 years were similar between arms. Fernando and colleagues
50
published the updated results at a median follow-up of 4.38 years. Only 17 of 222 patients experienced local progression, and there was no significant difference in the time to local recurrence or in the type of local recurrence with the addition of brachytherapy. Interestingly, there was no significant improvement in local recurrence rate or OS with the addition of brachytherapy even among patients with potentially compromised surgical margins. Intraoperative brachytherapy did not significantly worsen pulmonary function or dyspnea at 3 months and did not result in an increased rate of adverse events51
compared to surgery alone. To our knowledge, there have been no recent reports regarding an overall trend in the use of intraoperative brachytherapy; however, our general sense is that it has been offered less throughout the United States in recent years. Because the ACOSOG Z4099 sublobar resection with or without brachytherapy to SBRT in high-risk operable patients was closed as a result of poor accrual in 2013, it is unclear at this time what role this treatment modality will play in the future.- Fernando H.C.
- Landreneau R.J.
- Mandrekar S.J.
- et al.
The impact of adjuvant brachytherapy with sublobar resection on pulmonary function and dyspnea in high-risk patients with operable disease: preliminary results from the American College of Surgeons Oncology Group Z4032 trial.
J Thorac Cardiovasc Surg. 2011; 142: 554-562
Radiofrequency Ablation
RFA is a relatively new treatment option for patients with medically inoperable disease with primary NSCLC or metastatic lesions involving the pulmonary parenchyma. After initial success in the treatment of hepatic malignancies,
52
RFA was introduced in the treatment of patients with medically inoperable lung tumors and in those who refused surgery (Table 2).Table 2Studies Including Radiofrequency Ablation
| Study (Year) | No. Patients (No. Tumors) | Patients per Disease Stage | Tumor Location | Tumor Size | Follow-Up | LC Rate | 1 Year Survival | 2 Year Survival | OS | CSS | Complications |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Lee (2004) 57 | 30 (32) | 10 stage IA/B, 1 stage IIB, 15 stage III/IV, 4 Mets | Central 18 (56%), peripheral 14 (44%) | 5.2 ± 2.4 cm | 12.5 (range 1-24) mo | 38% with complete necrosis at least for 9 mo | NA | NA | Mean survival: <3 cm: 18.6 ± 2.2 mo; >3 cm: 11.3 ± 1.8 mo (P = .09) | NA | 10% major complication ARDS or severe PT all central tumor |
| Fernando (2005) 60 | 18 (21) | 9 stage I, 2 stage II, 3 stage III, 4 stage IV | Peripheral | Median 2.8 (range 1.2-4.5) cm | Median 14 mo | 61.9% | 83% | 83% | NA | PFS: mean and median intervals 16.8 and 18 mo; stage I, mean interval 17.6 mo | PT 38.9%, pneumonia 11.1%, air leak 5.6%, PE 5.6% |
| Hiraki (2006) 61 | 128 (342) | 25 primary, 317 Mets | Central 90 (26%), peripheral 252 (74%) | 1.7 ± 1.2 cm | Median 12 mo | 73% (1-30 mo after first ablation) | NA | NA | NA | NA | NA |
| Yan (2006) 62 | 55 | 26 stage I/II, 29 stage III/IV, colorectal pulmonary Mets | Central 10 (18%), peripheral 45 (82%) | <5 cm | 24 (range 6-40) mo | 62% (at time of 40 mo follow-up) | Stage I/II 92%, stage III/IV 79% | 3 years: stage I/II 69%, stage III/IV 38% | 33 mo median OS; actuarial survival: 1 year 85%, 2 years 64%, 3 years 46% | PFS: 15 mo | PT 29%, fever 11%, pleural effusion 7.2%, PCP 3.6% |
| Pennathur (2007) 64 | 19 | 11 stage IA, 8 stage IB | Peripheral | Mean 2.6 (range 1.6-3.8) cm | 29 mo | 58% at 27 mo | 95% | 68% | NA | NA | PT 63%, air leak 5% |
| Simon (2007) 65 | 153 (189) | 116 stage I NSCLC, 73 stage IV colorectal | NA | Mean 2.7 cm for LC; mean 6.1 cm for palliation | Median 20.5 mo | 1, 2, 3, 4, 5 years, 83%, 64%, 57%, 47%, 47% (<3 cm); 1, 2, 3, 4, 5 years, 45%, 25%, 25%, 25%, 25% (>3 cm) | Stage I 78%, stage IV 70% | Stage I 57%, stage IV 54% | 5 7: stage I 27%, stage IV 44% | NA | PT 28.4%, chest tube 9.8% |
| Ambrogi (2007) 65 | 50 | 30 stage I NSCLC, 14 stage IV | 1 cm from major blood vessels or airways | Mean 2.4 cm | 31 mo | 61% | NA | NA | Stage I NSCLC 28.9 mo, all 25 mo | NA | NA |
| Lencioni (2008) 66 | 106 (183) | 33 stage I NSCLC, 53 colorectal Mets, 20 other Mets | 1 cm from trachea, main bronchi, Right/left pulm artery | Mean 1.7 cm | Up to 2 years | 1 year: 88% | NA | NA | NSCLC: 70% at 1 year, 48% at 2 years; stage IV colorectal: 89% at 1 year, 66% at 2 years; other: 92% at 1 year, 64% at 2 years | NSCLC: 92% at 1 year, 73% at 2 years; stage IV colorectal: 91% at 1 year, 68% at 2 years; other: 93% at 1 year, 67% at 2 years | PT 20% |
| Lanuti (2009) 67 | 31 (34) | 29 T1N0, 5 T2N0 | Peripheral | 2.0 ± 1.0 cm | 17 mo | 68.5% at 17 mo | 85% | 78% | 3 years: 47% median OS 30 mo | DFS: 57% at 2 years, 39% at 3 years, median 25.5 mo | PT 13%, pneumonia 16%, pleural effusion 21% |
| Huang (2010) 58 | 329 (436) | 237 NSCLC (33 stage I, 50 stage II 109 stage III, 45 stage IV, 92 Mets) | NA | <3 cm: 253; 3-4 cm: 102; >4 cm: 81 | Median progression-free period, 21.6 mo | Overall 76.3%, >4 cm 58% | 68.2 | 35.3 | 80.1% at 1 year, 45.8% at 2 years, 24.3% at 5 years | NA | 34.3% of patients overall; pneumothorax in 19%, hemoptysis in 4.2%, 30 d mortality 0.6% |
| Beland (2010) 59 | 79 (79) | 79 NSCLC (56 stage IA, 13 stage IIB, 3 stage IIB, 4 stage IIIB, 3 stage) | Central 15 (19%), peripheral 64 (81%) | 2.5 (range 1-5.5) cm | Mean follow-up 16 mo | 57% (recurrent or residual tumor in 43%) | NA | NA | Median DFS 23 mo | NA | Adjuvant RT in 19 patients (24%); concomitant brachytherapy in 9 patients (11%) |
Abbreviations: ARDS = acute respiratory distress syndrome; ARDS = acute respiratory distress syndrome; CSS = cause-specific survival; DFS = disease-free survival; LC = local control; Mets = metastases; NA = not applicable; NSCLC = non–small-cell lung cancer; OS = overall survival; PCP = pneumocystis carinii pneumonia; PE = pulmonary embolism; PFS = progression-free survival; PT = pulmonary thrombosis; RT = radiotherapy.
The goal of RFA is to induce thermal injury to the tumor through electromagnetic energy deposition.
53
Alternating current produced by a radiofrequency generator moves from an active electrode inserted within the tumor to dispersive electrodes placed on the patient. During RFA, a high-frequency electrical current heats and coagulates tissue. The temperature within the tumor rises to > 60°C, resulting in instantaneous cell death via protein denaturation and coagulation necrosis.Advantages of RFA compared to resection include treatment in an outpatient setting and the ability to complete nonoperative probe placement via CT guidance with the use of local anesthesia. Damage to the surrounding normal tissues and lung parenchyma is limited as a result of the presence of air, which provides an insulating effect allowing for dissipation of the energy and protection of nearby normal tissues; however, the procedure can result in complications such as pneumothorax, hemoptysis, bronchopleural fistula, rib fracture, and tissue injury.
54
Limitations of RFA include the inability to treat tumors in close proximity to vascular structures and the size and location of the tumor. Vessels larger than 3 mm in diameter reduce the amount of energy delivered to the target as a result of the loss of heat through convection within the circulatory system, the so-called heat sink effect.
55
Size is a limiting factor, with evidence to suggest a loss of LC in over 50% of lesions greater than 3 cm in diameter. As the target volume increases, the periphery may not reach an ablative temperature, resulting in diminished response and impaired LC.56
Location is critical as a result of the risk of damage to adjacent nonpulmonary structures, including the esophagus and trachea. Finally, post-RFA recovery from thermally induced inflammation may require several months and may result in difficulty in interpreting tumor response with CT imaging.Recent studies have examined the results of RFA as definitive therapy for early stage NSCLC. Lee and colleagues
57
assessed the technical feasibility, efficacy, and complications of percutaneous CT-guided transthoracic RFA in the treatment of inoperable NSCLC and lung metastasis. Thirty patients with 32 lung tumors were evaluated. The average tumor size was 5.2 cm (range, 2.8 to 7.6 cm) and patients had a median follow-up time of 12.5 months. Each patient received a single ablation. The complete necrosis rate (assessed by enhancement on CT imaging and read by an experienced radiologist) in the study was reported at 38%. Tumors smaller than 3.0 cm in diameter demonstrated higher complete necrosis rates compared to tumors larger than 5.0 cm (100% vs. 8%) with a median survival of 18.6 ± 2.2 months compared to 11.3 ± 1.8 months, respectively (P = .09). The authors reported a 10% rate of major complications, including 2 pneumothoraces requiring tube thoracotomy and 1 patient with acute respiratory distress syndrome.Huang and colleagues
58
performed a retrospective review of 329 patients with 436 lung tumors (237 primary and 92 metastatic lung tumors) treated with RFA as a result of refusal of surgery or inability to undergo surgical resection. RFA resulted in a median progression-free interval of 21.6 months. Local progression occurred in 23.7% of patients, with a significant difference in the risk of progression in tumors > 4 cm (P = .01). OS at 1, 2, and 5 years was 68.2%, 35.3%, and 20.1%, respectively, with a low 30-day mortality of 0.6%. A second study evaluated 79 patients with 79 primary lung tumors treated with RFA to include 35 patients with stage IA and 7 patients with stage IB NSCLC.59
The study included 19 patients (24%) and 9 patients (11%) treated with adjuvant external beam radiotherapy and concomitant brachytherapy, respectively. The median OS was 23 months and the overall recurrence rate 43% (34 of 79), with local failure as the dominant pattern, occurring in 38% (13 of 34). Increasing size of tumor and higher disease stage were significant for increased likelihood of disease recurrence.Fernando and colleagues
60
studied 21 tumors in 18 patients with a median tumor size of 2.8 cm. Each patient received 1 ablation, with CT and positron emission tomography utilized to evaluate response and recurrence. At a median follow-up of 14 months, the LC rate was 61.9%. One- and 2-year survival rates were 83% and 83%, with median progression-free survival (PFS) of 16.8 months. Hiraki and colleagues61
reported on 342 tumors in 128 patients with an average tumor size of 1.7 cm. For the 342 tumors, the authors performed 225 ablative sessions to include 49 repeat sessions for the treatment of local progression. Chemotherapy was administered for 193 tumors. With a median follow-up time of 12 months, the nonactuarial LC rate was 73%. The 2-year LC rate was 66% for tumors that were ablated once and 78% for those ablated more than once. They found that tumor size > 2 cm and the use of an internally cooled electrode were independent risk factors for local progression.Yan and colleagues
62
reported on 55 tumors (26 patients with stage I/II NSCLC) in 55 patients with an average tumor size of less than 5 cm. With a median follow-up of 24 months, the overall LC rate was 62%. The median OS time for the entire cohort was 33 months with a median PFS of 15 months. The subgroup with stage I/II NSCLC demonstrated a 1-year survival of 92% and a 3-year survival of 69%. Multivariate analysis demonstrated that lung metastasis > 3 cm was independently associated with a reduced OS (P = .003). Ambrogi and colleagues63
studied 50 tumors in 50 patients with a mean tumor size of ≤ 5.0 cm. The average follow-up time was 31 months, and the LC was nearly identical, at 61%. Another similar experience was reported by Pennathur et al64
with a documented local progression rate of 42% and 2-year OS of 49% after treatment of 19 patients with stage I NSCLC.Simon and colleagues
65
evaluated 153 consecutive patients with 189 primary NSCLCs (n = 116) or stage IV colorectal pulmonary metastasis (n = 73) to determine the long-term survival, local tumor progression, and complication rates after CT-guided RFA. Mean tumor size was 2.7 cm for tumors treated with curative intent and 6.1 cm for tumors treated with palliative intent. At a median follow-up of 20.5 months, the 1-, 2-, 3-, 4-, and 5-year LC rates for tumors < 3 cm in diameter were 83%, 64%, 57%, 47%, and 47%, respectively. For tumors > 3 cm, the 1-, 2-, 3-, 4-, and 5-year LC rates were 45%, 25%, 25%, 25%, and 25%, respectively. Stage I patients had 1-, 2-, and 5-year survival rates of 78%, 57%, and 27%, whereas the rates for colorectal pulmonary metastasis were 70%, 54%, and 44%, respectively. These results underscore the highly selective nature of patients chosen for this therapy in that outcomes varied widely based on tumor size and disease stage.Lencioni and colleagues
66
described 183 tumors in 106 patients with a mean tumor size of 1.7 cm. Patients were divided into 3 groups: NSCLC (n = 33), colorectal metastasis (n = 53), and other metastasis (n = 20). Each patient received 1 RFA treatment. The reported 1-year LC rate was 88%, and 1- and 2-year OS rates for patients with NSCLC were 70% and 48%, respectively, and 89% and 66% for patients with metastases from a colorectal primary lesion. Patients with stage I NSCLC had a 2-year OS and CSS of 75% and 92%, respectively. Lanuti et al67
reviewed 34 tumors in 31 patients with an average tumor size of 2 cm. At a mean follow-up time of 17 months, the LC rate was reported as 68.5%. The 4-year survival rate was 47% with a DFS at 2 and 3 years of 57% and 39%, respectively. As previously noted, the size of the target lesion is an important consideration in patient selection for RFA.68
Simon and colleagues65
demonstrated a 3-year LC of 57% in tumors < 3 cm in diameter compared to 25% in tumors > 3 cm in diameter. Bilal et al69
performed a literature search to compare the results of RFA and SBRT in the treatment of early stage medically inoperable NSCLC. On the basis of a review of 16 representative publications, the authors concluded that SBRT resulted in improved 5-year OS and decreased local progression compared to RFA, 48% versus 20.1%-27%, and 3.5%-14.5% versus 23.7%-43%, respectively.In summary, RFA has generally been associated with inferior LC compared to surgery and SBRT, where 3-year LC rates approximate 80% to 95%. Further studies with larger sample sizes and adequate follow-up are necessary to better delineate the role of this emerging modality. Trials such as ACOSOG Z4033, designed to evaluate RFA in the treatment of high-risk patients with early stage NSCLC, will help determine which patients this procedure will help most. This trial has completed accrual, but survival and recurrence data have not yet matured.
Microwave Ablation
MWA is a second heat-based ablation technique, similar to RFA in application and technique. MWA can be delivered either percutaneously under CT guidance or via open surgical or laparoscopic techniques. In contrast to RFA, thermocoagulation of the target lesion is a result of an electromagnetic wave that produces excitation and oscillation of water molecules within the tissue surrounding the probe (antenna). Given the properties of the electromagnetic wave, MWA does not require a grounding pad, as intratumoral temperatures can be measured through placement of a separate thermocouple located adjacent to the microwave antenna.
70
, 71
Theoretical advantages of MWA over RFA include enhanced thermocoagulation of tumor cells as a result of improved energy deposition in aerated lung and increased heating near blood vessels. MWA allows for increased intratumoral temperatures with generation of a larger ablation zone (up to 2 cm from the probe tip) in a shorter period of time compared to RFA.
72
Additionally, MWA may permit improved treatment of both peripheral and central lesions as a result of a reduction in pain with the use of microwaves and minimal heat sink effect associated with vasculature. Similar to RFA, MWA is associated with risk of pneumothorax, postprocedural pain, hemoptysis, and, rarely, pulmonary toxicity. Relative contraindications for both RFA and MWA include possible interference with the electromagnetic current of implantable cardiac devices and unpredictable pattern of ablation as a result of the presence of surgical clips.70
, 73
, 74
Much like RFA, MWA was first implemented as a treatment strategy for hepatic tumors,
75
with gradual expansion into the treatment of pulmonary lesions. Feng et al76
reviewed the results of MWA in the treatment of 28 lesions in 20 peripheral lung cancer patients (8 primary and 12 metastatic disease). With an overall response rate of 57.1%, a more than 50% ablation was noted in 13 (46.4%), with complete response in 3 (10.7%). No significant adverse effects or complications were observed. Wolf and colleagues77
retrospectively reviewed the results of percutaneous CT-guided MWA in 82 lung lesions in 50 patients. With a mean follow-up of 10 months, the 1-year LC was 67%, with 26% of the patients demonstrating residual disease at the ablation site. Kaplan-Meier analysis demonstrated an actuarial survival at 1, 2, and 3 years of 83%, 73%, and 61%, respectively. Interestingly, cancer-specific mortality was not significantly affected by index size of larger than 3 cm or the presence of residual disease.Limited outcome data are available to support the use of MWA in the treatment of early stage NSCLC. As with RFA, MWA can be considered in the treatment of recurrent disease or in combination with other techniques to provide palliation of progressive pulmonary lesions. Future studies will, we hope, clarify the role of MWA in the treatment of high-risk NSCLC.
Percutaneous Cryoablation
PCT, another thermal-based ablative technique, utilizes cold temperatures as opposed to heat. The therapeutic role of cryoablation is based on the Joules-Thompson effect with the utilization of a gas, typically argon, which rapidly decreases to subzero temperatures (as low as −150°C) upon transition from a liquid to gaseous state. Experiments have demonstrated that a 2 to 3 mm diameter probe can result in a freeze area 2 to 3 cm in diameter and 4 cm in length. The probe temperature is measured potentiometrically with a needle placed approximately 2 mm from the tip. The freeze cycle is alternated with a thaw cycle, during which helium gas is administered to raise the temperature to approximately 40°C. The diameter and number of probes and the number of freeze/thaw cycles is dependent on the size, location, and clinical scenario.
The alternating freeze/thaw cycles of PCT result in cell death through both direct and indirect mechanisms. Rapid freezing results in formation of both intracellular and extracellular ice crystals, which disrupt the cell membrane and internal cellular processes. Indirect actions include vasoconstriction and occlusion of blood vessels resulting from osmotic changes and local tissue edema resulting in hypoxic tissue injury and coagulative necrosis.
56
, 78
, 79
, 80
, Additionally, cryoablation generates immunologic interactions and promotion of inflammatory cytokines,82
which may also exert a tumoricidal effect.Similar to RFA, PCT is recommended for lesions less than 3 cm as a result of difficulty with probe geometry in the treatment of large or irregular lesions, resulting in increased risk of recurrence. Successful ablation requires generation of a cryozone approximately 1 cm beyond the radiographically imaged tumor and a minimum isotherm of −20°C to result in cell death. PCT also suffers from the heat/cold sink effect, as with RFA.
In contrast to RFA, PCT is recommended for treatment of central tumors due to the relative resistance of collagenous architecture allowing for minimization of damage to adjacent organs.
83
Because of the delayed effects of cryotherapy, with development of nonhemorrhagic necrosis 8 to 14 days after treatment, the technique is not recommended for immediate debulking or management of an obstructing lesion.84
Cryotherapy may result in less pain in the treatment of tumors along the pleura and chest wall.56
The main complications of PCT include pneumothorax, hemorrhage, fistula formation, and bronchospasm, similar to RFA and MWA.78
, 85
Cryoablation initially gained acceptance in the intraoperative management of prostate and hepatic malignancies. Bronchoscopically directed cryotherapy has been utilized since the 1980s to treat superficial endobronchial lesions in both the definitive and palliative settings.
56
Maiwand and Asimakopoulos86
treated 521 patients with advanced obstructive tracheobronchial malignant tumors with cryotherapy and demonstrated that the treatment provided a palliative benefit with reduction in hemoptysis, cough, dyspnea, and chest pain in 76.4%, 69%, 59.25%, and 42.6% of patients, respectively. Improvement in 1 or more symptoms was noted in 86% of patients, with a median survival of 8.2 months. Other investigators have demonstrated the safety and efficacy of cryotherapy delivered via direct thoracoscopic guidance in the treatment of symptomatic inoperable lung cancer.Wang and colleagues
78
reported their experience on the use of PCT in the treatment of 234 pulmonary masses in 187 patients. The review included a heterogeneous patient population, with 89% diagnosed with advanced pulmonary malignancies in which prior treatment, including surgery, chemotherapy, and radiotherapy, had failed. Stage I and II primary lung tumors represented only 17 and 20 lesions, respectively. The authors concluded that CT-guided PCT may allow for improved therapeutic benefit compared to other ablative modalities, with a low procedural morbidity and accurate treatment localization. Kawamura and colleagues85
performed PCT in the treatment of 35 metastatic lung tumors in 20 patients over 22 sessions. With a median follow-up of 21 months, 20% of tumors recurred, with complications including pneumothorax in 11 sessions, hemoptysis in 8, and 1 case of phrenic nerve palsy. One-year survival was estimated at 89.4%.Choe and colleagues
87
investigated the efficacy of PCT and RFA in the management of 76 lesions in 65 patients with inoperable lung malignancies. Sixty-seven total lesions were treated with RFA, while 9 tumors were managed with PCT. Twenty patients in the RFA group and 3 patients in the PCT cohort were diagnosed with stage I NSCLC. With a median follow-up of 20.8 months, complete ablation was achieved in 76.2% of patients treated with RFA and 85.7% in the PCT group when the lesion was less than 3 cm in diameter. Larger lesions resulted in an inferior complete response rate of 43.3% and 66.7% in the RFA and PCT patients, respectively.Zemlyak et al
88
compared the results of RFA, sublobar resection and PCT in 64 patients with biopsy-positive stage I NSCLC deemed unfit for lobectomy. With a median follow-up of 33 months, 3-year CSS for sublobar resection, RFA, and PCT was 90.6%, 87.5%, and 87.5%, respectively. OS was 60.8%, 87.1%, and 77%, respectively. The authors noted a trend toward increased local (33%) and regional/distant recurrence (25%) in the RFA cohort. Yamauchi and colleagues89
retrospectively reviewed the results of 34 tumors in 22 patients with histologically proven stage I lung cancer. With a median follow-up of 23 months (range, 12 to 68 months), local tumor progression occurred in only 1 tumor (3%). The mean maximal tumor diameter was 1.4 cm. The median OS was 68 months, with 2- and 3-year DFS of 78% and 67%, respectively.The limited number of early stage NSCLC patients and the predominantly retrospective nature of the PCT literature does not permit appropriate comparison of RFA or SBRT. The report from Zemlyak et al
88
included only 9 patients treated with PCT, of which only 3 lesions were stage I NSCLC. Although the toxicity profile appears favorable and PCT may allow for improvement in the therapeutic ratio compared to RFA and MWA, generalization of this treatment modality in the definitive management of early stage NSCLC requires prospective evaluation with larger patient numbers and longer follow-up.Photodynamic Therapy
The utilization of PDT in the treatment of thoracic malignancies has increased over the last several years.
90
PDT involves the systemic delivery of a photosensitizing agent, typically porphyrin based, followed by direct excitation of the compound by a wavelength of light that correlates to the absorption band of the infused drug. The resulting photodynamic reaction results in the production of singlet oxygen and local reactive cytotoxic agents. The mechanism of cell death is multifaceted and believed to be due to direct cell killing via both apoptosis and cell necrosis. Indirect damage also occurs as a result of injury to the tumor vasculature and a local inflammatory response with associated antitumor immunogenic factors.90
, 91
, 92
, 93
Reported complications include hemorrhage, respiratory compromise, and skin burns related to systemic administration of the agent and exposure to UV light.84
Simone and colleagues
90
at the University of Pennsylvania published an exhaustive review of the role of PDT in the treatment of NSCLC. As described, the role of PDT in early stage NSCLC is generally limited to small (≤ 1 cm) endobronchial lesions without extracartilaginous invasion or lymph node involvement. The ability for light to penetrate the target tissue and activate the photosensitizing agent is a limiting factor in the role of PDT, with therapy most effective in the treatment of minimally invasive lesions.94
, - Wisnivesky J.P.
- Yung R.C.
- Mathur P.N.
- et al.
Diagnosis and treatment of bronchial intraepithelial neoplasia and early lung cancer of the central airways: diagnosis and management of lung cancer, 3rd ed: American College of Chest Physicians evidence-based clinical practice guidelines.
Chest. 2013; 143: e263S-e277S
95
Furuse et al
96
published the results of a phase 2 study with porfimer sodium (Photofrin II) in the treatment of 59 early stage, centrally located squamous cell carcinomas in 49 patients. Overall, 85% of the lesions demonstrated a complete response, with a median duration of response of 14 months. The complete response rate was 100% in smaller tumors < 5 mm compared to 38% in tumors > 20 mm. Kato et al97
treated 264 central early stage NSCLC in 204 patients, of which 70% were stage 0% and 30% were stage I. The maximum tumor dimension was < 20 mm in 87% of patients, with a reported complete response rate of 95% in tumors with a length < 5 mm, 94% in those 5 to 9 mm, and a decrease to only 44% in lesions > 20 mm. Several series report complete response rates with PDT ranging from 62% to 100%, with the longitudinal length of the tumor being an important determinant in response.94
- Wisnivesky J.P.
- Yung R.C.
- Mathur P.N.
- et al.
Diagnosis and treatment of bronchial intraepithelial neoplasia and early lung cancer of the central airways: diagnosis and management of lung cancer, 3rd ed: American College of Chest Physicians evidence-based clinical practice guidelines.
Chest. 2013; 143: e263S-e277S
Okunaka et al
98
evaluated the role of PDT as a novel therapy for patients with peripheral lung tumors < 1 cm in size deemed unfit for surgery or radiotherapy. Patients received a photosensitizer followed by CT-guided percutaneous insertion of needles with internal catheters to allow for light administration. Nine patients were treated, with 7 experiencing partial remission and 2 experiencing pneumothorax.PDT is considered a safe and effective method of treatment for noninvasive (dysplasia and carcinoma-in-situ) and early stage central NSCLC and in patients requiring focal palliative therapy.
94
Extensive endobronchial and aerodigestive lesions may require a debulking procedure before the application of PDT as a result of limited light penetration. Insufficient data exist to support a role in the management of peripheral NSCLC without an endobronchial or central component.- Wisnivesky J.P.
- Yung R.C.
- Mathur P.N.
- et al.
Diagnosis and treatment of bronchial intraepithelial neoplasia and early lung cancer of the central airways: diagnosis and management of lung cancer, 3rd ed: American College of Chest Physicians evidence-based clinical practice guidelines.
Chest. 2013; 143: e263S-e277S
Stereotactic Body Radiotherapy
In patients with early stage NSCLC unable to tolerate surgical resection, radiotherapy has historically been considered the standard alternative treatment. Definitive external beam radiotherapy, delivered in standard once-daily fractions (1.8 to 2 Gy per fraction), resulted in long-term survival rates of 15% to 30%, with local failure rates exceeding 50%.
8
, 99
, 100
Sibley99
evaluated the results of 10 studies assessing the treatment of medically inoperable NSCLC patients with radiotherapy. With a median dose of 60 to 66 Gy, 25% of patients died of intercurrent disease, 30% with distant metastatic disease and 30% with local failure alone, illustrating the lack of primary tumor control with conventional fractionation.The published results of primary radiotherapy are inferior to surgical resection for several key reasons. First, the disease of the majority of patients treated with primary radiation is inoperable as a result of significant life-limiting medical comorbidities. Thus, the surgical and radiation groups essentially consist of 2 very different patient populations with a significant bias in regard to long-term outcomes and OS. Second, surgical patients typically undergo formal pathologic staging and assessment of regional lymph nodes allowing for consideration of adjuvant therapy to include postoperative radiation and/or chemotherapy as indicated. In contrast, patients treated with definitive radiation may never undergo surgical lymph node sampling with treatment options based exclusively on clinical and radiographic staging. Finally, the historical doses delivered with conventional radiotherapy may have been biologically inadequate for long-term LC.
Mehta et al
101
described the radiobiologic rationale for dose per fraction escalation based on evidence that doses in excess of 85 Gy are required to achieve 50% long-term LC when utilizing standard fractionation (2 Gy per fraction). Thus, the total dose to the tumor must be increased from the standard range of 60 to 66 Gy in order to deliver an adequate biologic effect to improve the LC of these tumors. With conventional fractionation, a protracted radiation schedule requiring periods of up to 10 weeks may be required to deliver such a dose. However, the total duration of radiotherapy is of pivotal importance in the treatment of NSCLC, with modeling to suggest a 1.6% per day loss in survival with prolongation of the treatment beyond 6 weeks as a result of accelerated tumor repopulation.101
, 102
, 103
Stereotactic radiosurgery was first developed in the 1950s for the treatment of small intracranial lesions or the ablation of functional intracranial regions
104
with the intent of delivering a high dose of radiation in a single session with submillimeter-level precision through the utilization of stereotactic guidance. SBRT represents an extension of these principles to sites outside of the central nervous system. In 1994, Lax et al105
provided the first description of a stereotactic frame developed at Karolinska University Hospital and discussed the methodology for delivery of stereotactic radiotherapy to extracranial tumors. Subsequently, Blomgren et al106
were the first to report on the use of the stereotactic frame and fixation device in the treatment of 42 tumors (liver and lung) in 32 patients with a reported LC of 80% during a follow-up period ranging from 1.5 to 38 months.SBRT, also known as stereotactic ablative body radiotherapy (SABR), is characterized by the use of a rigid and reproducible immobilization device intended to minimize and regularize respiratory and patient motion with collection of precise measurements to account for tumor motion during both treatment planning and delivery of each fraction. The use of highly conformal dose distributions with rapid dose fall off and daily image guidance allow for a reduction in the high-dose treatment volume, allowing for decreased irradiation of surrounding normal tissues with an associated reduction in toxicity.
107
Treatment is typically delivered in 3 to 5 fractions over a 1- to 2-week period, ranging on average from 10 to 20 Gy per fraction (although single-fraction and more protracted regimens are also in use). With SBRT, the radiobiologic principle of tumor repopulation is of diminished importance as a result of shorter overall treatment times, often less than 2 weeks,108
and the ability to deliver an increased biologic effective dose (BED) compared to traditional fractionation.109
The resulting BED of SBRT is typically in excess of 100 Gy, in contrast to a BED of 79.2 Gy with standard fractionation (66 Gy in 2 Gy per fraction), assuming an alpha/beta ratio of 10 for acutely responding tissue (tumor). Fowler and colleagues110
, 111
at the University of Wisconsin provided the first analysis of the radiobiologic implications of SBRT and the role of linear quadratic modeling to describe the effect of doses up to 23 Gy per fraction on both the tumor and surrounding normal tissues.McGarry et al and Timmerman et al
112
, 113
, 114
demonstrated the safety of SBRT in the treatment of early stage NSCLC in a phase 1 dose-escalation trial conducted at the University of Indiana. The investigators utilized an extracranial frame with incorporation of a fiducial stereotactic coordinate system and an abdominal compression device designed to minimize tumor motion through a reduction in respiratory excursion. Thirty-nine medically inoperable patients with clinical stage IA or IB (T1 or T2, ≤ 7 cm) NSCLC received SBRT with peripheral tumor doses initiated at a dose of 24 Gy (8 Gy per fraction × 3 fractions) with escalation up to 60 Gy (20 Gy per fraction × 3 fractions) in the T1 cohort without exceeding the maximum tolerated dose. Patients in the T2 cohort, with tumors larger than 5 cm, experienced excessive toxicity at the 72 Gy dose (24 Gy per fraction × 3 fractions) with the maximum tolerated dose defined at 66 Gy (22 Gy per fraction × 3 fractions).A phase 2 trial
114
followed this experience to further assess toxicity and LC in inoperable patients with early stage NSCLC. Seventy patients were treated with doses ranging from 60 to 66 Gy in 3 fractions as per the results of the phase 1 study. With a median follow-up of 17.5 months, the reported LC at 2 years was 95% with a 2-year OS of 54.7% and median OS of 32.6 months. Grade 3 to 5 toxicity was documented in 14 patients with a 2-year freedom from severe toxicity in 83% with peripheral lesions compared to 54% in patients with perihilar/central tumors. Bradley et al115
reviewed the results of 91 patients enrolled onto a prospective database, with 83 patients referred for SBRT as a result of underlying comorbidities and the remaining 8 patients refusing surgery. Eighty-three tumors were peripheral and 8 were central (defined as ≤ 2 cm from the bronchus or esophagus or located adjacent to the brachial plexus). Peripheral tumors received 54 Gy (18 Gy per fraction × 3 fractions), while central tumors received a reduced dose of 45 Gy (9 Gy per fraction × 5 fractions) based on the toxicity data from Timmerman et al.112
, 114
The median tumor diameter was 2 cm with no tumor > 5 cm. Fifty-eight patients with T1N0, 22 patients with T2N0, 2 patients with T3N0 (chest wall), and 6 patients with T1N0M1 disease were included. With a median follow-up of 18 months, the 2-year LC was 86% with distant metastasis or second lung cancer as the predominant pattern of failure.In 2010, Timmerman and colleagues
116
reported the results of the Radiation Therapy Oncology Group (RTOG) 0236, a phase 2 trial with inclusion of 55 medically inoperable patients with peripheral tumors < 5 cm (T1-2, N0) treated with SBRT. With a median follow-up time of 34.4 months, the 3-year LC, DFS, and OS were 97.6%, 48.3%, and 55.8%, respectively. The rate of disseminated recurrence at 3 years was 22.1% (11 of 55), with only 2 patients experiencing regional failure. Treatment-related morbidity was relatively low, with grade 3 events occurring in 12.7% and grade 4 in 3.6% of patients. There were no reported SBRT-related patient deaths, possibly as a result of ineligibility of patients with central tumors.At the American Society of Radiation Oncology's (ASTRO) 56th annual meeting, Timmerman et al presented updated 5-year data from the RTOG 0236 trial. The updated results showed only 4 primary tumor failures among 55 patients, resulting in a 5-year primary failure rate of 7%. The rate of local recurrence was 20%, owing primarily to intralobar recurrence. Additionally, 5-year locoregional and distant recurrence rates were 38% and 31% respectively. Updates on toxicity revealed 2 additional episodes of grade 3 or higher, but no grade 5, toxicities.
117
This update is significant because it shows that local recurrence rates with SBRT appear to be similar to lobectomy series at 5 years, with minimal increased severe toxicity after 3 years. The RTOG 0236 trial served as the basis for RTOG 0813, a phase 1/2 protocol designed to determine a safe and effective dose for central tumors. The study was closed to accrual in 2013, and results have not yet been published.Since the first experience of Timmerman and colleagues, a number of platforms capable of SBRT have come into popular use, including standard linear accelerator-based options, CyberKnife, Tomotherapy, Viewray, and proton-based options. Additionally, various immobilization devices, respiratory-tracking, and tumor motion-gating options have been developed. Each has advantages and disadvantages, and they vary considerably in the costs of installation and maintenance, required treatment time, beam angle capabilities, and beam modifiers. As the technology has developed, an expanding number of institutional reports of SBRT for early stage NSCLC are now available and are summarized in Table 3.
Table 3Studies Including Stereotactic Body Radiotherapy
| Author (Year) | No. Patients | Patients per Disease Stage | Tumor Location | Tumor Size | Dose | BEDiso | Follow-Up | Local Control Rate | 1 Year Survival | 2 Year Survival | OS | CSS | Complications or Toxicities | Lung Function Criteria |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| McGarry (2005) 113 | 47 | 19 stage IA, 28 stage IB | No location criteria, all patients accepted | ≤7 cm | T1 stratum 24-60 Gy; T2 stratum 24-72 Gy to 80% isodose | T1: 43.2-180 Gy; T2: 43.2-244.8 Gy | T1: 27.4 mo, T2: 19.1 mo | 78% (9/10 occurred at doses ≤16 Gy per fraction) | NA | NA | NA | NA | Grade 3 or more in 72 Gy cohort | Inoperable: 14 patients oxygen dependent |
| Le (2006) 118 | 32 | 21 NSCLC, 11 metastatic | No location criteria, all patients accepted | 2.0-6.2 cm tumor diameter | 15-30 Gy, <20 Gy (n = 10), 25 Gy (n = 20), 30 Gy (n = 2) | 37.5-120 Gy | Not defined | 91% (>20 Gy cohort), 54% (<20 Gy cohort) | 89% | NA | NA | NS | Increased pulmonary toxicity >25 Gy with prior RT and volumes >50 cm3 | NA |
| Hof (2007) 109 | 42 | 17 stage IA, 21 stage IB, 4-2 stage B | Peripheral | Stage IA <3 cm, stage IB >3 cm | 15-24 Gy to 80% isodose in single fraction | 24-81.6 Gy | 15 mo | 1 year 89.5%, 2 years 67.9%, 3 years 67.9% | 74.5% | 65.4% | 3 years 37.4% | 1 year 70.2%, 2 years 49.1%, 3 years 49.1% | Only mild reactions; no grade 3 or 4 toxicities | FEV1 at least 0.8 L |
| Koto (2007) 119 | 31 | 19 T1, 12 T2 | 30 peripheral, 1 central | Median 2.5 cm | 20 patients: 45 Gy/3/1 wk; 11 patients;: 60 Gy/8/2 wk | 45 Gy group: 113 Gy; 60 Gy group: 105 Gy | 32 mo | 3 years: stage IA 77.9%, stage 40% | NA | NA | 3 years 71.7% | 3 years 83.5% | 24 patients grade 1 pneumonitis; 3 patients grade 2 acute pneumonitis; 1 patient grade 3 acute pneumonitis | NA (not surgical candidates, refused surgery) |
| Onishi (2007) 120 | 257 | 164 stage IA, 93 stage IB | No location criteria, all patients accepted | Median 2.8 (range 0.7-5.8) cm | 18-75 Gy in 1-22 fractions | 111 Gy (median), 215 patients: ≥100 Gy median (117 Gy median), 42 patients: <100 Gy (79.6 Gy median) | 38 mo | 86%: stage IA 87.8%, stage IB 82.8% (P = .21); BED ≥100 Gy: 91.6%; BED <100 Gy: 57.1% (P <.001) | NA | NA | 3 years 56.8%, 5 years 47.2%, (5 years BED >100 Gy: 53.9%, BED <100 Gy: 19.7%) (P <.05) | 3 years 76.9%, 5 years 73.2% | 1 patient chronic segmental bronchitis and wall thickening (atelectasis); 2 patients grade 3 esophagitis; 3 patients grade 3 or 4 dermatitis; 4 patients rib fracture adjacent to tumor | ECOG: 0-109, 1-103, 2-39, 3-6 |
| Lagerwaard (2008) 121 | 206 | 129 T1, 90 T2 | 63% UL, 31% LL, 6% ML, peripheral 689 | ≤6 cm | 93-20 Gy/3, 99-12 Gy/5, 27-7.5 Gy/8 | 3-180 Gy, 5-132 Gy, 8-105 Gy | 12 mo | 97% | 81% | 64% | 3 years, ∼50% (figure 1) | 1 year 83%, 2 years 68%, (other survival rates reported) | 64 patients fatigue, 25 patients local chest wall pain, 19 patients nausea, 12 patients dyspnea, 12 patients cough, 6 patients grade 3 or higher pneumonitis | FEV1 54% |
| Baumann (2009) 122 | 57 | 40 T1, 17 T2 | Peripheral | 2.5 (range 0.6-5) cm | 45 Gy/5/3, 15 × 3 at 67% isodose line | Peripheral 113, central 211 | 35 mo | 3 years 92% | 86% | 65% | 3 years 60% | 1 year 93%, 2 years 88%, 3 years 88% | 16 patients grade 3 | Mean FEV1 64% |
| Inoue (2009) 123 | 115 | 93 T1, 22 T2 | Peripheral | Median 2 (range 0.5-4.5) cm | 30-70 Gy in 2-10 fractions | 106 (range 56-141) Gy | 14 mo | ≤2 cm: 96.6%, >2 cm: 94.7% | NA | 3 years: ≤2 cm 89.8%, >2 cm 60.7% | 5 years: ≤2 cm 89.8%, >2 cm 53.1% | NA; OS reported based on 2 different size groups | ≤2 cm: 2 patients grade 2; >2 cm: 5 patients grade 2 and 3 patients grade 3; 1 patient grade 5 | ECOG 0-2 (WHO) |
| Guckenberger (2009) 124 | 124 (159 lesions) | 118 Mets, 41 NSCLC (13 stage IA, 19 stage IB, 9 T3N0) | Central, TW, peripheral NSCLC6, 9, 26; Mets, 16, 24, 78 | CTV 29 cm3, PM 8 cm3 | 12.5 Gy/3% to 65% isodose, 26 Gy/1% to 80% isodose, 10 Gy/3% to 65% isodose | 84 Gy, 94 Gy, 60 Gy | Mean 18 mo, median14 mo | 3 years 83% | NA | NA | 3 years: 37% NSCLC, 16% Mets | 3 years: NSCLC 59% | Acute (24 patients), 19 patients, 1 patient grade 2, 3 pneumonitis, 2 patients II PT, 2 patients II PE, late (6 patients), 3 patients II dyspnea, 2 patients II PT, 1 patient III esophageal ulcer | Karnofsky index 77, 89 |
| Fakiris (2009) 125 | 70 | 34 T1, 36 T2 | 48 peripheral, 22 central | ≤7 cm | T1: 20 Gy/3; T2: 22 Gy/3 | T1: 180 Gy; T2: 211 Gy | 50.2 mo | 3 years, 88.1% | NA | NA | 3 years 42.7% | 3 years 81.7% | 6 patients grade 3; 1 patient grade 4; 5 patients grade 5 | FEV1 <40%, DLCO <40% |
| Bradley (2010) 115 | 91 | 58 T1N0M0, 22 T2N0M0, 2 T3N0M0, 6 T1N0M1 | 83 peripheral, 8 central | Median 2 (range 1-5) cm | Peripheral 18 Gy/3; central 9 Gy/5 | 18 Gy group: 151 Gy; 9 Gy group: 85.5 Gy | 18 mo | 2 years, 86%, 3 years, ∼86% (figure 1) | NA | NA | 3 years ∼60%, 4 years ∼50% | 3 years ∼73%, 4 years ∼65% (figure 4) | 3 patients grade 2 pneumonitis; 4 patients rib fracture or chest wall pain; 1 patient brachial plexopathy | FEV1 46%, DLCO 49% |
| Timmerman (2010) 116 | 55 | 44 T1, 11 T2 | Peripheral | <5 cm | 18 Gy/3 | 151.2 Gy | 34.4 mo | 87.2% | ∼87% | ∼75% | 3 years 55.8% | 3 years 48.3% | 7 patients grade 3; 2 patients grade 4 | FEV1 <40%, DLCO <40% |
| Haasbeek (2010) 127 | 193 (203 tumors) | 118 T1, 85 T2 | 83 peripheral, 8 central | Median2 (range 1-5) cm | 69-20 Gy/3, 101-112 Gy/5, 33-7.5 Gy/8 | 3-180 Gy, 5-132 Gy, 8-105 Gy | 12.6 mo | 3 years 89% | 85.7% | NA | 3 years 45.1%; median OS 32.5 mo | ≥3 pneumonitis 2.1%, cough 5.7%, chest wall pain 2.6%, dyspnea 5.2% | Severe COPD in 25%; 80% inoperable; 20% declined surgery |
Abbreviations: BED = biologic effective dose; COPD = chronic obstructive pulmonary disease; CSS = cause-specific survival; CTV = clinical target volume; DLCO = carbon monoxide diffusing capacity; ECOG = Eastern Cooperative Oncology Group; FEV1 = forced expiratory volume in 1 second; LL = lower lobe; Mets = metastases; ML = middle lobe; NA = not applicable; NSCLC = non–small cell lung cancer; OS = overall survival; PE = pulmonary embolism; PT = pulmonary thrombosis; RT = radiotherapy; UL = upper lobe; WHO = World Health Organization.
Le et al
118
completed a phase 1 dose-escalation study designed to investigate the optimal single-fraction SBRT dose in the treatment of inoperable lung tumors. Thirty-two patients (21 T1-T2N0 NSCLC and 11 metastatic tumors) received SBRT with tumor doses initiated at 15 Gy with escalation to a dose of 30 Gy. The 1-year OS was 85% with a 1-year freedom from local progression of 91% with doses > 20 Gy compared to 54% in patients who received less than 20 Gy (P = .03). The overall rate of complications increased with doses greater than 25 Gy with increased risk of pulmonary toxicity in patients with treatment volumes greater than 50 cm3 and in those with a history of pulmonary radiation.Hof and colleagues
109
reported on 42 patients with stage IA (n = 17), IB (n = 21), or IIB (n = 4) NSCLC. Patients were treated with 15 to 30 Gy prescribed to the isocenter with the 80% isodose covering the planning target volume. With a median follow-up of 15 months, LC and OS rates at 1, 2, and 3 years were 89.5%, 67.9%, and 67.9%, and 74.5%, 65.4%, and 37.4%, respectively. Koto and colleagues119
reported on 31 patients with a median tumor size of 2.5 cm with a median follow-up of 32 months. Patients were treated with either 60 Gy in 8 fractions (if the tumor was close to an organ at risk) or 45 Gy in 3 fractions. The 3-year LC rate for patients with stage IA disease (n = 19) was 77.9%, compared to 40% for stage IB disease (n = 12). The 3-year OS and CSS rates for the entire cohort were 71.7% and 83.5%, respectively.Onishi and colleagues
120
reported on an amalgamation of multi-institutional data from Japan that included 257 patients (164 patients with stage IA disease and 93 with stage IB disease) with a median tumor size of 2.8 cm (range, 0.7 to 5.8 cm). Of the 257 patients, 99 had medically operable disease but refused surgery. The median follow-up period for the entire cohort was 38 months. Given the heterogeneity of radiotherapy dose prescriptions, the cohort was dichotomized into 2 groups, with 215 patients receiving ≥ 100 Gy BED and the other 42 patients receiving < 100 Gy BED. The overall LC rate for the entire cohort was 86% (87.8% for stage IA and 82.8% for IB, which was deemed to be significantly different, P = .21). The group that received ≥ 100 Gy BED had a LC rate of 91.6%, while those who received a BED < 100 Gy had a LC rate of only 57.1% (P < .001). The 3- and 5-year OS for the entire cohort was 56.8% and 47.2%, respectively. The 5-year OS for the BED ≥ 100 Gy cohort was 53.9%, compared to only 19.7% for < 100 Gy (P < .05). With a median follow-up of 58 months, the operable group treated with SBRT alone to a BED > 100 Gy demonstrated 5-year OS and local PFS rates comparable to historical lobectomy controls.85
Lagerwaard and colleagues
121
published the results of 206 patients with tumor sizes of ≤ 6 cm treated with a variety of fractionation schemes based on tumor stage and risk of toxicity to surrounding normal tissue (20 Gy × 3, 12 Gy × 5, and 7.5 Gy × 8 fractions). With a median follow-up of 12 months, the LC was 97% with median OS at 1 and 2 years of 81% and 64%, respectively. The 1- and 2-year CSS were 83% and 68%. Severe late toxicity was observed in less than 3% of patients. Baumann and colleagues122
reported on 57 patients with an average tumor size of 2.5 cm (range, 0.6 to 2.5 cm). The median follow-up was 35 months with a 3-year LC was 92%. In terms of OS, the 1-, 2-, and 3-year rates were 86%, 65%, and 60%, respectively. The CSS at these time intervals was 93%, 88%, and 88%, respectively.Inoue et al
123
studied 115 patients with a median tumor size of 2 cm at a median follow-up of 14 months. Tumors ≤ 2 cm had a LC of 96.6%, compared to 94.7% for larger tumors. OS rates for the group with ≤ 2 cm tumors at 3 and 5 years were both 89.8%. The OS of the group with tumors > 2 cm at 3 and 5 years were 60.7% and 53.1%, respectively. Guckenberger and colleagues124
reported on 124 patients in their study, which included 41 patients with NSCLC and the remainder with pulmonary metastases. Average tumor size for those with NSCLC was 8 cm3. The median follow-up time was 14 months, and 3-year LC was 83%. For the NSCLC patients in the study (n = 41), the 3-year OS and CSS were 37% and 59%. This group also evaluated the impact of BED and found that 3-year LC was 89% versus 62% in favor of BED > 100 Gy. Fakiris and colleagues125
reported on 70 patients with tumors ≤ 7 cm. The average follow-up time was 50.2 months, and the LC at 3 years was 88.1%. The OS and CSS at 3 years were 42.7% and 81.7%, respectively.A retrospective report from the Cleveland Clinic explored the effect of 2 different fractionations on tumor control and toxicity. Eighty-six consecutive patients (with 94 lesions) with medically inoperable stage I NSCLC received either 50 Gy in 10 Gy fractions or 60 Gy in 20 Gy fractions. The change in fractionation reflected a change in institutional practice based on date of treatment delivery rather than a clinical treatment selection. LC for the 50 and 60 Gy cohorts at 1 year were 97.3% and 100%, and OS was 83.1% and 76.9%, respectively, which were not significantly different. The only significant difference between the cohorts was the incidence of mild (grade 1 or 2) chest wall toxicity, which was higher in the 60 Gy group (18% vs. 4%, P = .028). Thus, the authors concluded that tumor control was not affected by this change in fractionation, but chest wall toxicity was increased with 60 Gy in 20 Gy fractions.
126
Haasbeek et al127
retrospectively reviewed the role of SBRT in patients ≥ 75 years of age with early stage NSCLC (118 T1 tumors and 85 T2 tumors) deemed medically inoperable or in those who refused surgery. Two hundred three tumors were treated in 193 patients with utilization of 3 risk-adapted fractionation schemes based on the location of the tumor (20 Gy × 3, 12 Gy × 5, and 7.5 Gy × 8 fractions). OS at 1 and 3 years was 86% and 45%, respectively, with a median survival of 32.5 months. The 3-year LC was 89%. The authors noted minimal acute toxicity with uncommon severe late toxicity with grade 3 or higher late toxicity in less than 10% of patients.Bishawi and colleagues
39
reviewed 30 patients with stage I and II NSCLC treated with SBRT alone (60 Gy in 3 fractions). The main focus of the review was to assess the effects of SBRT on FEV1 and DLCO. FEV1 before and after treatment did not change dramatically in patients with and without COPD (39 ± 5 vs. 40 ± 9, P = .4; 77 ± 0.5 vs. 73 ± 24, P = .9). DLCO, on the other hand, significantly improved for those who did not have COPD but not for patients with COPD (60 ± 24 vs. 69 ± 22, P = .022; 49 ± 13 vs. 50 ±, P = .8).Sher and colleagues
40
compared costs of SBRT, 3-D conformal radiotherapy, and RFA for treatment of medically inoperable stage I NSCLC. In their study, a model was created to describe the health status of a 65-year-old man with early stage NSCLC treated with 1 of the 3 modalities listed above. It was assumed that patients received supportive care at recurrence. Data for cost and recurrence were adapted from the literature and utility values were computed. The incremental annual quality-adjusted life years' value of SBRT over RFA and 3-D chemoradiotherapy were US$14,000 and US$6000, respectively.From the literature, it can be concluded that LC and OS for patients with NSCLC treated with SBRT are superior to conventional radiotherapy and appear similar to surgical outcomes. However, given their predominantly retrospective nature, inherent selection biases, and limited follow-up, it is important to complete further prospective trials. Another important caveat is that SBRT is commonly performed in medically inoperable patients in which histologic confirmation through biopsy is often avoided as a result of the procedure's risks. In the Haasbeek et al
127
experience, for instance, the rate of histologic confirmation of malignancy was only 39%, which they report as being in line with other similar studies. In the absence of pathology, institutions and national organizations are developing consensus guidelines for establishing a diagnosis of malignancy using radiographic criteria such as 18F-fludeoxyglucose uptake and documented growth. A recent publication by Louie et al128
describes an inventive model for comparison between several approaches in this situation.To address several of the critical issues surrounding SBRT, the RTOG conducted a number of recent trials. The RTOG 0915 study compared 2 SBRT fractionation schedules including 48 Gy in 4 fractions and 34 Gy in a single fraction. The study met its accrual objective and was presented as an abstract at the 2013 ASTRO annual meeting with 20.6 months of follow-up. At 1 year, the single-fraction regimen met prespecified criteria with respect to adverse events and tumor control; thus, this regimen has been selected as the experimental arm for a planned phase 3 trial.
The RTOG 0618 trial studying the use of SBRT in patients with operable, early stage disease closed to accrual in 2010, and the RTOG 0813 trial studying the treatment of centrally located tumors was closed in 2013. Both studies met their accrual objectives, with data maturing at the present time. Unfortunately, the RTOG 1021/ACOSOG Z4099 study comparing sublobar resection with or without brachytherapy to SBRT in high-risk operable patients was closed in 2013 as a result of slow accrual, as were the Dutch ROSEL and Accuray STARS trials, both comparing lobectomy and SBRT.
Conclusion
In summary, patients with early stage NSCLC deemed to be at high risk or medically inoperable, or patients who otherwise refuse lobectomy, have new options for treatment with evidence to support promising results and manageable toxicities. Such techniques, including RFA and SBRT, provide options for patients unable to undergo lobectomy or even limited resection, and they allow for the possibility of improved LC and OS compared to historical controls. Further studies are required to better define the optimal treatment of patients with early stage NSCLC to include a definitive comparison of SBRT to surgical resection in patients with operable disease.
Disclosure
The authors have stated that they have no conflicts of interest.
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Article info
Publication history
Published online: April 22, 2015
Accepted:
April 14,
2015
Received in revised form:
April 8,
2015
Received:
October 20,
2014
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