Risk-Based Local Radiation Therapy in Oligometastatic Non-small Cell Lung Cancer in the Era of Immunotherapy: A Multicentric Cohort Study.

[PURPOSE] The role of consolidation radiation therapy (cRT) in patients with oligometastatic non-small cell lung cancer (oligo-NSCLC) without driver genetic alterations remains uncertain in the era of immunotherapy (IO). This study aimed to evaluate the efficacy of cRT combined with IO at various programmed death ligand 1 (PD-L1) expression levels using data from a multicenter cohort.

[METHODS AND MATERIALS] Patients with oligo-NSCLC without driver genetic alterations, treated with IO with or without cRT, and with available PD-L1 tumor proportion scores (TPS) were retrospectively reviewed across 3 institutions. Inverse probability of treatment weighting (IPTW) was applied to control for bias.

[RESULTS] This study included 240 patients, among which 30.4%, 35.0%, and 34.6% patients had PD-L1 TPS 0, 1% to 49%, and ≥50%, respectively. After inverse probability of treatment weighting adjustment, subgroup analysis revealed that cRT significantly improved progression-free and overall survival in the PD-L1 TPS 0% to 49% group (hazard ratio [HR]: 0.59; 95% CI, 0.38-0.92; P = .009; HR: 0.59; 95% CI, 0.35-0.99; P = .016; respectively); however, no additional benefit was found in the PD-L1 TPS ≥50% group. Multivariate Cox analysis identified PD-L1 TPS score as an independent prognostic factor only in the IO group (HR: 0.54; 95% CI, 0.34-0.88; P = .01). Adding cRT to IO in patients with PD-L1 TPS 0% to 49% improved survival to levels comparable with those of patients with PD-L1 TPS ≥50%. Moreover, cRT was associated with lower rate of progression at original sites in the overall cohort (HR: 0.51; 95% CI, 0.32-0.81; P = .005), particularly in the PD-L1 TPS 0% to 49% subgroup (HR: 0.38; 95%: CI, 0.21-0.68; P = .001).

[CONCLUSIONS] The addition of cRT to IO may improve survival outcomes for driver-negative oligo-NSCLC patients with low or negative PD-L1 expression. The PD-L1 TPS may be a valuable biomarker to optimize cRT patient selection in the era of immunotherapy. Further prospective investigations into this stratification strategy are warranted.