Consolidative and salvage thoracic radiotherapy (TRT) in extensive-stage small-cell lung cancer (ES-SCLC) with first-line chemoimmunotherapy: a retrospective study from a single cancer center

Extensive-stage small-cell lung cancer (ES-SCLC) continues to have poor outcome despite the survival improvements achieved by chemoimmunotherapy. Controversy exists regarding the survival effectiveness of consolidative thoracic radiotherapy (cTRT), and the role of salvage thoracic radiotherapy (sTRT) remains unexplored in the immunotherapy era. To address these issues, we conducted this retrospective study to investigate the impacts of cTRT and sTRT in ES-SCLC, and to compare the survival benefits of the two treatment regimes. ES-SCLC patients without baseline brain metastases receiving standard first-line chemoimmunotherapy were included in our study, cohorts were divided by treatment with cTRT, sTRT and no TRT. Kaplan-Meier survival curve and log-rank test were performed for comparison of survival between different groups. Univariable and multivariate analyses were carried out for further estimating the survival effectiveness of TRT. A total of 100 ES-SCLC patients without baseline brain metastases were included in our study, with 24 (24.0%) were allocated to the cTRT group, 18 (18.0%) were allocated to the sTRT group, and 58 (58.0%) to the No TRT group. cTRT dramatically decreased the rate of intrathoracic failure compared to sTRT and No TRT (29.4% vs. 60.0%). Moreover, patients who received cTRT had better overall survival (OS) compared to those who did not receive cTRT (median OS, not reached vs. 14.1 months; HR=0.40, 95% CI: 0.22-0.70, P=0.01). However, cTRT did not show significantly superior OS compared to sTRT alone (median OS, not reached vs. 21.0 months; HR=0.67, 95% CI: 0.27-1.66, P=0.39). In contrast, patients with only thoracic oligo-progression receiving sTRT (N=13) harbored better OS compared to patients with the same progression pattern in No TRT group (N=20) (median OS, 28.6 vs. 13.8 months; HR=0.44, 95% CI: 0.20-0.98, P=0.04). In conclusion, our study demonstrated in the chemoimmunotherapy era that cTRT greatly reduced the rate of initial intrathoracic failure and significantly improved the OS of ES-SCLC. Additionally, sTRT showed similar OS benefits with cTRT, and exhibits better OS compared to No TRT.