Efficacy and safety of consolidative thoracic radiotherapy after first-line chemoimmunotherapy in patients with extensive-stage small-cell lung cancer: a retrospective cohort study.

Background: Thoracic radiotherapy (TRT) has shown potential benefits in improving local control and overall survival (OS) in chemotherapy-responsive small-cell lung cancer (SCLC) cases. However, its role in the era of chemoimmunotherapy remains underexplored. In the current era of immunotherapy, this study evaluated the efficacy and safety of consolidative TRT (cTRT) in patients with extensive-stage SCLC (ES-SCLC) and assessed its impact on OS. Additionally, the optimal radiotherapy dose and fractionation schemes were also explored.

Methods: In this retrospective cohort study, 124 patients with ES-SCLC diagnosed at Taizhou Cancer Hospital between January 2019 and November 2023 were categorized into cTRT and non-cTRT groups. We compared the baseline characteristics, treatment processes, and survival outcomes between the two groups. Moreover, cTRT subgroups of different radiotherapy doses and fractionation schemes were formed and compared in terms of baseline characteristics, radiotherapy efficacy and safety, patterns of recurrence after radiotherapy, and survival outcomes. OS was selected as the primary endpoint for observation. Differences in OS between the groups were analyzed using log-rank tests. Univariable and multivariable Cox regression analyses were performed to identify factors correlated with OS in the overall patient cohort.

Results: The baseline characteristics between the two groups (cTRT and non-cTRT) were generally comparable, with the following significant differences: the cTRT group had a lower proportion of females (1.7% vs. 15.2%, P=0.02), lower levels of neuron-specific enolase (NSE, median: 15.87 vs. 32.00 ng/mL, P=0.009), and higher sodium concentrations (median: 140.50 vs. 138.25 mmol/L, P=0.01). Additionally, the cTRT group underwent more first-line treatment cycles (median: 4.00 vs. 3.00, P=0.001). Compared with the non-cTRT group, the cTRT group had a longer OS [median survival 15.5 vs. 10.5 months; hazard ratio (HR) =2.0497; 95% confidence interval (CI): 1.3548-3.1010; P<0.001]. There were no significant differences in survival outcomes associated with the different radiotherapy dosage or fractionation schedules. The most common adverse event was neutropenia, but no severe treatment-related deaths occurred. Multivariable Cox analysis revealed that the sodium concentration (HR =0.8751; 95% CI: 0.7944-0.9642; P=0.007), initial treatment response (HR =0.7022; 95% CI: 0.4949-0.9964; P=0.048), total number of systemic treatment cycles (HR =0.5501; 95% CI: 0.3618-0.8364; P=0.005), and whether to receive cTRT (HR =1.7484; 95% CI: 1.1033-2.7708; P=0.02) were independent prognostic factors for OS.

Conclusions: cTRT improved the OS of patients with ES-SCLC and exhibited manageable associated toxicity. Further research is needed to confirm the effect of radiotherapy dose and fractionation scheme selection on treatment outcomes.