Association of radiotherapy with survival across metastatic patterns in metastatic small cell lung cancer in the immunotherapy era: a SEER analysis.

BACKGROUND: Radiotherapy (RT) combined with chemoimmunotherapy may have synergistic effects and improve treatment efficacy and survival in extensive-stage small cell lung cancer (ES-SCLC). However, its association with survival appears to be inconsistent across different metastatic patterns. METHODS: Patients with metastatic SCLC diagnosed between 2020 and 2023 were identified from the Surveillance, Epidemiology, and End Results database. Propensity score matching (PSM), Kaplan-Meier analysis, and Cox regression were used to evaluate the association between RT and cancer-specific survival (CSS). Inverse probability of treatment weighting (IPTW) and overlap weighting were performed as sensitivity analyses. RESULTS: A total of 4707 patients were included. Liver metastasis was the most common site-specific metastasis (44.1%), followed by bone (42.1%), brain (30.1%), and lung metastasis (16.1%). Multi-organ metastases without brain involvement were the most common metastatic pattern (21.2%), followed by other/unspecified (16.0%) and multi-organ metastases with brain involvement (15.5%). After 1:1 PSM, additional RT was associated with higher CSS in the liver only (HR, 0.68; 95% CI, 0.51-0.91; P = .009), lung only (HR, 0.55; 95% CI, 0.38-0.80; P = .002), multi-organ without brain (HR, 0.77; 95% CI, 0.64-0.92; P = .005), and other/unspecified cohorts (HR, 0.67; 95% CI, 0.54-0.82; P < .001). No significant association was observed in the bone only, brain only, or multi-organ with brain cohorts. IPTW and overlap weighting analyses yielded consistent results. CONCLUSIONS: In the immunotherapy era, among patients with metastatic SCLC receiving first-line chemoimmunotherapy, the association between additional RT and CSS may vary across metastatic patterns.