Evaluating the role of consolidative chest radiotherapy after chemo-immunotherapy in extensive-stage small cell lung cancer: A retrospective study.

Abstract

8023 Background: Consolidative chest radiotherapy (XRT) after chemoimmunotherapy may provide benefits in extensive-stage small cell lung cancer (ES-SCLC) due to the condition’s high sensitivity to radiation. Current guidelines suggest chest XRT for ES-SCLC patients who respond to chemotherapy, given its association with improved 2-year overall survival (OS), and reduced progression and recurrence rates. However, its role in the era of chemo-immunotherapy in ES-SCLC remains unclear. Methods: Data from the National Cancer Database (NCDB) for ES-SCLC patients diagnosed between 2017 and 2020 were analyzed (n=24,676). Cases included those treated with multi-agent chemotherapy, with data for T, N, and M status, and chest XRT. Exclusion criteria included survival <30 days, limited-stage SCLC cases, and missing key data elements. The primary outcome was OS from diagnosis, analyzed using Kaplan-Meier and multivariate Cox regression models. Propensity Score Matching (PSM) was performed to compare outcomes in ES-SCLC patients receiving chest XRT after immunotherapy versus immunotherapy alone, adjusting for T, N, and M status, institution, sex, and CD score. A p-value of <0.05 was considered statistically significant. Results: The study stratified patients in two groups: 10,437 immunotherapy receivers and 14,239 not receiving immunotherapy. The proportion of chest XRT receivers was similar across both groups (13% vs. 14%, p=0.17). Receipt of XRT was significantly associated with younger age (<70), female sex, T3-4 stage, N2-N3, and M1a status; (p<0.05). Chest XRT was associated with a significant increase median OS in both groups: immunotherapy (13.1 months vs. 9.8 months; p<0.001) and non-immunotherapy (11.6 months vs. 8.4 months; p<0.001). XRT was an independent predictor of better OS in both groups after controlling for other covariates (HR 0.72 and 0.66; p<0.001). PSM analysis of 1,399 patients receiving XRT and 1,399 receiving immunotherapy alone confirmed the OS benefit of XRT after immunotherapy (13.1 months vs. 9.4 months; HR 0.63, p<0.001) with a 3-year survival of 16% (95%CI: 13.7-18.3%) vs 7% (95%CI: 5.3-8.7%), respectively. Conclusions: Our analysis shows that consolidative chest XRT is associated with improved overall survival in patients with ES-SCLC, especially when combined with chemoimmunotherapy. These findings are hypothesis-generating and support ongoing randomized studies evaluating consolidative radiotherapy in the chemoimmunotherapy era. Multivariable Cox regression analyses for overall survival in ES-SCLC. Factor Immunotherapy + Immunotherapy - HR (95% CI) HR (95% CI) Chest XRT (Yes/No) 0.72 (0.68-0.77) 0.67 (0.64-0.71) p-value P<0.0001 P<0.0001 ES, extensive stage; SCLC, small cell lung cancer; HR, hazard ratio; CI, confidence interval; Ref, reference; CD, Charlson-Deyo; XRT, radiation.