Role of thoracic radiation in extensive stage small cell lung cancer: a NCDB analysis

Prognosis of extensive stage small cell lung cancer (ES-SCLC) remains poor. Previous randomized trials suggested consolidation chest radiation (CXRT) has a modest survival benefit; however, its role in subgroups of ES-SCLC, especially ipsilateral pleural effusion (IPE), is unknown. Using National Cancer Database (NCDB), 283,347 ES-SCLC cases diagnosed between 2004 and 2017 were screened. Eligible cases must have been staged with 7th edition of staging system and have information about clinical T and N stage, and minimum follow-up of one month. Role of CXRT was examined in M1a, M1b, and IPE subgroups. Surveillance, Epidemiology, and End Results Program (SEER) was analyzed as independent validation. Univariate, multivariate analyses were conducted with cox proportional hazard model. A P value < 0.05 was considered as statistically significant. A total of 36,762 were analyzed. In both M1a and IPE groups, use of CXRT was significantly associated with younger age, female sex, non-academic institution, and clinical T stage. Both univariate and multivariate analyses showed that use of CXRT demonstrated significantly longer overall survival in all the groups, with lower hazard ratios in M1a and IPE groups than M1b (univariate hazard ratio 0.62, 0.56, and 0.72, respectively). Propensity score analysis of IPE group showed the survival advantage with hazard ratio of 0.54. Use of SEER data validated its survival advantage of CXRT in IPE group. This retrospective database analysis suggests M1a and IPE subgroups have more survival benefit of CXRT than M1b subgroup. Further studies are warranted to confirm the hypothesis.