Efficacy and safety of thoracic radiotherapy for extensive stage small cell lung cancer after immunotherapy in real world

Purpose The immunotherapy combined chemotherapy has been the standard treatment strategy for extensive-stage small lung cancer (ES-SCLC). The CREST trial reported consolidative thoracic radiotherapy (cTRT) improved overall survival (OS) for ES-SCLC with intrathoracic residual after chemotherapy. This study was aimed to evaluate the efficacy and safety of TRT for ES-SCLC after first line chemoimmunotherapy.Methods ES-SCLC patients who received immunotherapy in Zhejiang Cancer Hospital has been retrospectively analyzed between January 2020 and November 2021. Patients were assigned to receive either TRT or no TRT. Oligo-metastatic disease was defined as 3 or less discrete distant metastases with no more than 2 organs. Propensity score matching (PSM) was performed in two groups. The main outcome measures were progression-free survival (PFS), local recurrence-free survival (LRFS) and OS.Results 111 patients with ES-SCLC were enrolled in this study, the median OS was 14 months. 39 patients received TRT after chemoimmunotherapy (TRT group) and 72 patients did not receive TRT (no TRT group). TRT group improved OS (HR 0.58, 95% CI 0.34–0.99, p = 0.0445), PFS (HR 0.59, 95% CI 0.38–0.90, p = 0.0149) and LRFS (HR 0.3, 95% CI 0.16–0.56, p = 0.0001). Further sub-cohort analysis, TRT significantly improved LRFS in patients with oligo-metastasis and without liver metastasis. This trend persisted after PSM. However, OS in oligo-metastasis and non-liver metastasis subgroup was without significant difference.Conclusion TRT improved LRFS, PFS and OS for ES-SCLC with thoracic residual after chemoimmunotherapy with well tolerated toxicity.