Real-world efficacy of first-line immunochemotherapy combined with thoracic radiotherapy in elderly patients with extensive-stage small cell lung cancer: a single-center retrospective study

Background Extensive-stage small cell lung cancer (ES-SCLC) carries a poor prognosis. Although first-line chemoimmunotherapy (IO+ChT) is standard, evidence in elderly patients (≥70 years) and the role of thoracic radiotherapy (TRT) remain limited.Methods We retrospectively analyzed 1,276 ES-SCLC patients, including 350 elderly patients, treated with first-line therapy. To reduce TRT-related bias, a 4-month landmark analysis and propensity score matching (PSM; n = 780) were performed. Overall survival (OS) and progression-free survival (PFS) were primary endpoints.Results IO+ChT significantly improved OS compared with chemotherapy alone in the overall cohort and in elderly patients (both p < 0.01). In the matched elderly cohort, TRT markedly prolonged OS (HR = 0.56, p < 0.001) and emerged as the strongest independent prognostic factor. A significant interaction between TRT and immunotherapy was observed (pinteraction < 0.001), with survival benefits predominantly in patients receiving TRT. TRT was associated with increased mild hematologic toxicity but no excess severe adverse events or pneumonia.Conclusion First-line IO+ChT confers survival benefit in ES-SCLC, including elderly patients. The receipt of consolidative TRT is associated with potentially favorable survival outcomes and an acceptable safety profile, suggesting that integrated treatment strategies may be considered in fit elderly patients, pending prospective validation.