Clinical outcomes and synergistic effect between radiotherapy and immunotherapy in patients with extensive-stage small cell lung cancer: a real-world study

Background Patients with extensive-stage small cell lung cancer (ES-SCLC) experience significant therapeutic challenges and limited survival rates. This study aimed to investigate the efficacy of combining immunotherapy (IT) with chemotherapy (CT) for treating ES-SCLC and to explore the synergistic effect between radiotherapy (RT) and IT. Methods This retrospective analysis examined patients with ES-SCLC who received treatment at three centers. Furthermore, propensity score-matched (PSM) analysis was conducted. The Kaplan-Meier method and Cox proportional hazards regression were used to compare the survival outcomes. Results A total of 257 eligible patients with ES-SCLC were included in the analysis. Among all patients, the median overall survival (mOS) was 18.0 m in the chemoimmunotherapy (CT + IT) group and 15.7 m in the CT group (p = 0.208). The median real-world progression-free survival (mrwPFS) was 7.7 m and 6.8 m (p = 0.043) in the CT + IT and CT group, respectively. Moreover, the mOS was 22.0 m in the chemoradiotherapy (CT + RT) group and 13.6 m in the CT group (p < 0.001). The mrwPFS was 7.4 m and 6.0 m (p = 0.175) in the CT + RT group and CT group, respectively. The multivariate analyses revealed that sex, liver metastasis and RT were independent prognostic factors for OS (p < 0.05), while liver metastasis and IT were found to be independent predictive factors of real-world progression-free survival (rwPFS) (p < 0.05). After PSM, the mOS was 23.2 m in the CT + IT group and 13.0 m in the CT group (p = 0.008). The mrwPFS was 7.3 m and 6.2 m (p = 0.096) in the CT + IT group and the CT group, respectively. Moreover, the mOS was 21.4 m in the CT + RT group and 12.5 m in the CT group (p < 0.001). The mrwPFS was 7.3 m and 5.2 m (p = 0.220) in the CT + RT group and the CT group, respectively. Additionally, our study revealed that in the PD-1 group, RT significantly improved patient survival (36.0 m vs. 15.8 m, p = 0.041). Conclusion An increasing number of treatment options are being explored for ES-SCLC, and CT is the cornerstone of treatment for this disease. Combining CT with IT and RT has demonstrated remarkable efficacy and excellent safety profiles, and such treatments are worthy of further exploration.