2042 - Benefit of Consolidative Thoracic Radiotherapy Following First-Line Chemoimmunotherapy in Metastatic NSCLC: Based on PD-L1 Expression

Y. Ge¹, Y. Sun², J. Li², S. Wang², L. Wang², J. Wang³, J. Li⁴, X. Wang⁵, D. Wang², and A. Gao⁶; ¹Shandong University Cancer Center, Jinan, Shandong, China, ²Shandong Cancer Hospital And Institute,Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, ShanDong, China, ³Qilu Hospital of Shandong University, Jinan, ShanDong, China, ⁴Shandong Cancer Hospital And Institute, Jinan, ShanDong, China, ⁵Shandong Cancer Hospital and Institute, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, ShanDong, China, ⁶Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China

Purpose/Objective(s): PD-1/PD-L1 inhibitors combined with chemotherapy have been established as the standard first-line options in metastatic non-small cell lung cancer (NSCLC). Consolidative thoracic radiotherapy (cTRT) after systematic therapy significantly improved patient survival and was widely used in clinical practice in the pre-immunotherapy era. However, whether cTRT following first-line chemoimmunotherapy can improve patient outcome is still controversial. More importantly, the subpopulation who can benefit from cTRT is unknown. Materials/

Methods: Metastatic NSCLC patients who received first-line chemoimmunotherapy with or without subsequent cTRT from three cancer centers were retrospectively enrolled in the real-world study.. Based on PD-L1 expression, they were further divided into three groups: PD-L1 negative (TPS score <1%), PD-L1 low (TPS score 1-49%), and PD-L1 high (TPS score=50%) groups. Propensity score matching (PSM) with a 1:1:1 ratio was applied in three groups. The efficacy and safety were evaluated.
Results: A total of 424 patients were included, with 333 and 91 and patients in cTRT and no cTRT groups, respectively. Compared with patients in no cTRT group, those in cTRT group showed significantly improved median progression-free survival (mPFS) (15.8 months vs 12.2 months, P=0.002) and overall survival (mOS) (NA vs 27.73 month, P=0.023). After PSM, a total of 30 pairs of patients were enrolled in PD-L1 negative group, 29 pairs in PD-L1 low group, and 32 pairs in PD-L1 high group. For patients with negative PD-L1 expression, cTRT markedly prolonged PFS (median: 14.72 months vs 9.56 months, P=0.008), and numerically improved OS (median: 30.06 months vs 21.09 months, P=0.21). In those with low PD-L1 expression, cTRT significantly improved both PFS (median: 16.59 months vs 12.32 months, P=0.042) and OS (median: NA vs 24.97 months, P=0.034). However, in patients with high PD-L1 expression, no significant PFS (median: 18.81 months vs 15.8 months, P=0.913) and OS (P=0.892) differences were observed between cTRT and no cTRT groups. Further analysis on adverse events (AEs) revealed that patients receiving cTRT or not showed comparable AE occurrence. However, for those with high PD-L1 expression, cTRT generated higher rate of grade III-V pneumonia compared with no cTRT (18.8% vs. 3.1%).
Conclusion: cTRT following first-line chemoimmunotherapy prolongs PFS and OS in patients with negative and low PD-L1 expression. In those with high PD-L1 expression, cTRT can not bring survival benefit which might due to increased pneumonia occurrence.