2170 - The Value of Radiotherapy for Patients with Extensive-Stage Small Cell Lung Cancer Treated with First-Line Chemo-Immunotherapy

Y. Wang¹, Y. Zeng², X. Su¹, J. Jia¹, T. Zhou¹, Y. Lu¹, L. Zhao³, Z. Yang¹, X. Fu¹, and X. Cai¹; ¹Department of Radiation Oncology, Shanghai Chest Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China, ²Department of Radiation Oncology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China, ³Department of Radiation Oncology, Shanghai Chest Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China

Purpose/Objective(s): The CREST study showed that consolidative thoracic radiotherapy could improve the survival of patients with extensive-stage small cell lung cancer (ES-SCLC), but not clear in the era of immunotherapy. This real world study aimed to investigate the efficacy of the combined regimen and the value of early RT in ES-SCLC patients treated with first-line chemo-immunotherapy. Materials/

Methods: This retrospective study enrolled 375 patients with ES-SCLC treated with first-line chemo-immunotherapy from December 2018 to December 2022, whose survival data and adverse events data were collected. 76 patients who received RT before disease progression were defined as Early RT group, while the other 299 patients, called Late RT group, which consisted of 54 patients who received RT for salvage purpose (Salvage RT group) and 245 patients who did not receive RT (Non-RT group).
Results: The median progression free survival (PFS) and median overall survival (OS) of Early RT group and Late RT group were 11.4 months versus 6.1 months (HR=0.59, 95%CI 0.45-0.77; p<0.001) and 23.8 months versus 18.0 months (HR=0.50, 95%CI 0.34-0.73; P<0.01). The mPFS and mOS of Early RT group were also significantly longer than Non-RT group (all p<0.01). Compared to Salvage RT group, the Early RT group also had survival benefit in mPFS (11.4 months vs. 5.7 months, HR=0.33, 95%CI 0.22-0.52; p<0.001) and nearly significant benefit in mOS (23.8 months vs. 18.0 months, HR=0.58, 95%CI 0.33-1.03; p=0.06). However, Salvage RT group showed no survival benefit compared with Non-RT group (mOS, 18.0 months vs. 18.2 months, p=0.44). The multivariate analysis also demonstrated that Early RT was independent positive predictor for PFS and OS. There was no significant difference in adverse events between two groups.
Conclusion: Receiving RT before disease progression significantly improved PFS and OS with acceptable adverse events risk in ES-SCLC patients treated with first-line chemo-immunotherapy, while salvage RT after disease progression could not improve survival. This finding should be further verified by prospective randomized studies.