Local Ablative Therapy Combined with Pembrolizumab in Patients with Synchronous Oligometastatic Non-Small Cell Lung Cancer: A Recursive Partitioning Analysis

Purpose: This study aimed to evaluate the efficacy of local ablative therapy (LAT) combined with pembrolizumab in patients with synchronous oligometastatic non-small cell lung cancer (NSCLC) and to identify patients who would most benefit from LAT. Methods and Materials: We retrospectively identified patients diagnosed with synchronous oligometastatic NSCLC (≤5 metastatic lesions and ≤3 organs involved) and treated with first-line pembrolizumab between January 2017 and December 2022. Patients who underwent LAT, including surgery or radiotherapy at all disease sites, were compared with those who did not undergo LAT. A recursive partitioning analysis (RPA) model was developed using prognostic factors for progression-free survival (PFS). Results: Among the 258 patients included, 78 received LAT with pembrolizumab and 180 received pembrolizumab alone. The median follow-up duration was 15.5 months (range, 3.0–71.2). In the entire cohort, LAT was independently associated with significantly improved PFS (hazard ratio [HR], 0.64; P = 0.015) and overall survival (OS) (HR, 0.61; P = 0.020). In the propensity score-matched cohort (N = 74 in each group), the median PFS was 19.9 months and 9.6 months, respectively (P = 0.003), and the median OS was 42.2 months and 20.5 months, respectively (P = 0.045), for the LAT and non-LAT groups. Based on the RPA model, incorporating the number of metastatic lesions, performance status, and PD-L1 expression level, patients were stratified into three risk groups with distinct PFS. LAT significantly improved PFS and OS in the low- and intermediate-risk groups; however, no difference was observed in the high-risk group. LAT was more effective as a consolidative treatment following pembrolizumab initiation than as an upfront therapy. Conclusion: LAT combined with pembrolizumab was associated with higher PFS and OS compared to pembrolizumab alone in selected patients with synchronous oligometastatic NSCLC. The RPA model could serve as a valuable clinical tool for identifying appropriate patients for LAT.