PURPOSE: Appropriate local therapy may provide survival benefits in oligometastatic non-small cell lung cancer (NSCLC) patients receiving chemotherapy or targeted therapy. However, its roles in immunotherapy-treated patients have not been fully understood. METHODS: PD-1/PD-L1 inhibitor-treated metastatic NSCLC patients were enrolled in a prospective multi-center observational study (NCT04766515) from September 2020 to March 2023. Those without driver mutations, with measurable disease and harboring oligometastatic disease were included. Progression-free survival (PFS) and overall survival (OS) were compared between those with or without early local therapy (eLT). Moreover, eLT performed within or after 1 month of the initiation of PD-1/PD-L1 inhibitors was defined as concurrent- or sequential-LT, respectively. While, eLT targeting partial or all of the tumor lesions, was described as partial- or all-LT, respectively. RESULTS: Among the 180 patients identified, eLT was performed in 44, including concurrent-LT in 25 and all-LT in 19, respectively. With a median follow-up of 19.40 months, progressive disease occurred in 95 of the 136 patients without eLT. Compared to those without eLT, patients receiving eLT had significantly longer PFS (HR = 0.40, 95% CI 0.27-0.59, p <
0.0001) and OS (HR = 0.43, 95% CI 0.24-0.76, p = 0.02). Moreover, eLT was associated with improved survival after Cox analyses and propensity score matching. Meanwhile, sequential-LT, as well as all-LT, was associated with longer OS, when compared with concurrent-LT or partial-LT, respectively. CONCLUSIONS: Early local therapy, especially those performed after effective systemic therapy and targeting all tumor lesions, may prolong patient's survival in PD-1/PD-L1 inhibitor-treated oligometastatic NSCLC.