Elective nodal irradiation of high-risk regions is superior to involved field radiotherapy for limited-stage small cell lung cancer: a propensity score-matched retrospective study

Whether to omit elective nodal irradiation (ENI) in thoracic radiotherapy for limited-stage small cell lung cancer (LS-SCLC) remains controversial. The purpose of this study was to compare the efficacy and safety of ENI in high-risk lymph node regions compared to involved field radiotherapy (IFRT). We conducted a real-world retrospective study of LS-SCLC who received radical simultaneous dose-reduction radiotherapy (SDR-RT) and chemotherapy with or without immunotherapy from January 2018 to June 2023. Patients were divided into two groups based on the target volume delineation method: the ENI group and the IFRT group. Propensity score matching (PSM) was applied to balance the observable potential confounding factors between the two groups. The primary endpoints were overall survival (OS). A total of 540 eligible patients were enrolled, of whom 196 (36.3%) received ENI and 344 (63.7%) received IFRT. After PSM, the clinical characteristics of both groups were balanced, including 183 patients each. The median OS was 26.7 months in the IFRT group versus 37.7 months in the ENI group (P = 0.007). The median PFS was 8.7 months in the IFRT group versus 12.2 months in the ENI group (P = 0.006). The median DMFS was 12.3 months and 28.6 months in the two groups (P = 0.004), respectively. The incidence of radiation pneumonia (P = 0.646) and esophagitis (P = 0.493) were similar between the two groups. The 1-year cumulative incidence rate of ENF was 13.9% (95% CI 8.8–18.9%) in the IFRT group and 2.7% (0.4–5.1%) in the ENI group (Gray’s p < 0.001). ENI did not significantly increase the rate of adverse reactions compared to IFRT, while effectively prolonging OS, PFS, and DMFS, and reducing the risk of ENF in patients with LS-SCLC. Not applicable.