Efficacy and Safety of Thoracic Radiotherapy for Extensive-Stage Small-Cell Lung Cancer in the Era of Immunotherapy: A Real-World Study

To evaluate the safety and efficacy of consolidative thoracic radiotherapy (cTRT) for extensive-stage small cell lung cancer (ES-SCLC) patients in the era of first-line chemoimmunotherapy. A total of 100 patients with ES-SCLC who had responded to first-line platinum-based chemotherapy plus immunotherapy in our hospital from January 2018 to December 2021 were retrospectively analyzed. Patients were divided into cTRT and non-cTRT groups based on their receipt of cTRT. Categorical variables were compared using the Chi-squared test or Fisher’s exact test. Overall survival (OS) and progression-free survival (PFS) were calculated using the Kaplan-Meier method, with comparisons by the log-rank test. Univariate and multivariate analyses were employed to identify prognostic factors for OS using the Cox proportional hazards model. Cumulative incidence of local recurrence (LRR) was calculated using the Fine-Grey competing risks regression model. We finally enrolled 100 patients in our cohort including 48 patients received cTRT and 52 patients didn’t. The median age of the whole cohort was 62.5 years (range: 31-82). The median follow-up time was 20 months (95% CI：18.4-21.6 months). The cTRT group had significant longer OS compared with non-cTRT group (26 v 17 months, p = 0.006). OS rate at 1-year and 2-year were 84.4%, 58.5% and 70.6%, 19.5% in cTRT and non-cTRT group, respectively. The median PFS were 10.0 months and 8.0 months in cTRT and non-cTRT group, respectively (p = 0.005). Multivariate analysis identified cTRT as the only prognostic factor correlated with improved OS (HR = 0.48, p = 0.042). The incidence of cumulative local recurrence (LRR) at 1 year were 55.4% and 22.3% in non-cTRT and cTRT group, respectively (p < 0.001). Grade 3-4 adverse events (AEs) occurred in 50% of the whole cohort, with rates of 60.4% and 40.4% in the cTRT and non-cTRT groups, respectively. Hematological toxicities were the most common grade 3-4 AEs in both groups. 3 (6.3%) patients had grade 3 radiation esophagitis in the cTRT group. Treatment-related pneumonitis occurred in 11% of patients, all of which were grade 1-2. In the cTRT group, 5 patients had checkpoint inhibitor pneumonitis, and 5 patients had radiation pneumonitis, while 1 patient in the non-cTRT group experienced checkpoint inhibitor pneumonitis. The administration of cTRT is safe and holds potential benefits for ES-SCLC patients responding to first-line chemoimmunotherapy.