Feasibility and long-term outcomes of post-chemotherapy-based consolidation radiotherapy in extensive stage small-cell lung cancer

Background: The target definition of consolidation radiotherapy (RT) for extensive stage small-cell lung cancer (ES-SCLC) has not been standardized. This study aimed to demonstrate the feasibility of post-chemotherapy based consolidation RT in ES-SCLC.Methods: All ES-SCLC patients without initial brain metastases who completed >= 4 cycles of systemic therapy at Department of Radiation and Medical Oncology, Zhongnan Hospital of Wuhan University from 2012 to 2021 were included in this retrospective study. We correlated the site of first recurrence to the post-chemotherapy-based radiation volume (small-field). Relapse pattern, progression-free survival (PFS) and overall survival (OS) were compared between those received and did not receive consolidation RT.Results: A total of 152 patients were followed up for a median of 31.7 months (interquartile range [IQR], 23.9- 39.6 months). The median PFS and OS of the cohort were 8.3 months (IQR, 6.1-11.2 months) and 16.2 months (IQR, 9.9-24.9 months), respectively. Thoracic consolidation RT served not only as an independent prognostic factor for improved PFS in the entire cohort, but also significantly prolonged OS in the subgroup without syn-chronous liver metastases. Small-field consolidation RT markedly reduced in-field recurrences (hazard ratio [HR], 0.28 [95% CI, 0.12-0.38]; P < 0.001) without increasing out-of-field recurrences (HR, 0.40 [95% CI, 0.13-1.16]; P = 0.080). No relapse was observed at the margin of the targets. Treatment-related toxicities were moderate, with grade 3 acute radiation pneumonia, radiation esophagitis, and bone marrow suppression rates of 8.3%, 3.1%, and 12.5%, respectively. No grade 5 toxicity occurred.Conclusion: Small-field consolidation RT based on post-chemotherapy volume is safe and can significantly im -prove local control in ES-SCLC.