Survival after adjuvant radiation therapy in localized small cell lung cancer treated with complete resection

Objectives: To determine whether there is an overall survival (OS) benefit to the addition of thoracic radiation therapy (RT) following R0 resection of pathologic (p) T1 or pT2 N0 M0 small cell lung cancer. Methods: Using the National Cancer Database, we performed a retrospective cohort analysis. Patients who underwent R0 resection for pT1 or p2 N0 M0 small cell lung cancer, stratified by receipt of adjuvant thoracic RT, were compared on the basis of OS using hierarchical Cox Proportional hazards models. Results: Of 4969 patients diagnosed with pT1or pT2 N0 M0 SCLC from 2004 to 2014, 1617 (33%) underwent R0 resection of their primary tumor; of these resected patients, 146 (9.0%) had adjuvant thoracic RT. In unadjusted analysis, there was no significant difference in OS between groups (median survival: surgery alone, 62.2 months vs surgery+RT, 43.8 months; P =.1436). In multivariable analysis, RT was not associated with improved survival (P =.099). There was no significant difference in unadjusted or adjusted survival associated with receipt of RT in both a young and healthy cohort (P =.647 for unadjusted and P =.858 for adjusted) and a matched cohort (P =.867 and P =.954). In the matched cohort, improved OS was associated with younger patient age (adjusted hazard ratio, 1.07; 95% confidence interval, 1.04-1.10; P <.001), female sex (adjusted hazard ratio, 0.68, 95% confidence interval, 0.47-0.97; P =.035), and smaller tumors (adjusted hazard ratio, 1.02; 95% confidence interval, 1.01-1.03; P =.005). Having 2 or more comorbidities was associated with worse OS (adjusted hazard ratio, 2.16; 95% confidence interval, 1.21-3.86; P =.009). Conclusions: Although complete resection was accomplished in a minority of patients, for these patients, survival was good. The addition of thoracic RT to complete resection does not appear to confer additional survival benefit.