The Effect Of Thoracic Radiation Therapy On Overall Survival In Sclc: Findings From The National Cancer Database

This study aimed to report the effect of thoracic radiation therapy (TRT) on overall survival (OS) and examine whether the OS effect varies with the timing of TRT regarding systemic therapy in small cell lung cancer (SCLC). Patients with SCLC from the national cancer database (NCDB) 2005-2014 formed the base of the study population. TRT, dose and time effects were analyzed individually in patients treated with systemic therapy. Exploratory analysis on TRT survival effect was also performed for patients received immunotherapy. The primary endpoint was OS. Kaplan-Meier test was used for the OS analysis; Log rank was used for significant testing. A total of 169,397 patients were eligible. Median survival time (MST) was 8.5 months (mo). Younger age, female gender, non-African American, lower Charlson Comorbidity Index, and any TRT were all significantly associated with favorable OS in all stages (all Ps < 0.001). In 53,926 patients received TRT, the median survival was 14.9 mo vs 5.5 mo in 99,649 patients without TRT (P<0.0001). In 53,375 patients receiving non-immune systemic therapy, TRT significantly improved OS (MST 15.0 for TRT group vs 5.4 mo for non-TRT group, P < 0.0001). Compared to those receiving TRT before non-immune systemic therapy (n = 16,076, MST = 12.2 mo), patients with concurrent TRT (within 30 days of systemic therapy) had significantly better OS (n = 31,068, MST = 16.2 mo, P < 0.001), also significantly better than that of patients receiving TRT after systemic therapy (n = 1,036, MST = 15.7 mo, P <0.0001). Concurrent TRT has better survival than sequential systemic therapy followed by TRT in patients with stage I-III disease; while chemotherapy followed by TRT had better survival than concurrent TRT in stage IV disease (P<0.0001). In 338 patients treated with any immunotherapy, the median survival was 15.5 and 9.6 mo for TRT (n=104) and non-TRT group (n=234). In 94 patients treated with immunotherapy and TRT with treatment time available for analysis, the median survival was 20 mo (n = 21), 15.3 mo (n=42), and 15.9 months (n=31) for TRT followed by immunotherapy, concurrent TRT and immunotherapy followed by TRT (P = 0.656), respectively. This US national database validated the significant effect of TRT on OS in all stages of SCLC treated with systemic therapy. TRT with any systemic therapy followed by immunotherapy seemed to be associated with best survival.