Background: Pembrolizumab (pembro) is approved as first-line (1L) treatment for advanced NSCLC patients (pts) with PD-L1 tumor proportion score (TPS) ≥50% and as treatment for previously treated advanced NSCLC pts with PD-L1 TPS ≥1%. Here we present 3-y OS results for pts enrolled in KEYNOTE-001 (NCT01295827), the first trial evaluating pembro in advanced NSCLC pts. Methods: 550 pts received pembro 2 or 10 mg/kg Q3W or 10 mg/kg Q2W until intolerable toxicity, progression, or investigator or pt decision to withdraw. PD-L1 expression was assessed by IHC using the 22C3 antibody. Survival was assessed every 2 mo after treatment discontinuation. Results: 550 advanced NSCLC pts enrolled; 101 were first line (1L), and 449 were previously treated. As of the Sept 1, 2016, data cutoff, median follow-up duration was 34.5 mo (range, 25.7-51.5 mo); 8 (7.9%) 1L pts and 28 (6.2%) previously treated pts were still on treatment. 3-y OS was 26.4% (95% CI, 14.3%-40.1%) in 1L pts and 19% (95% CI, 15.0%-23.4%) in previously treated pts. 3-y OS rate and median OS by PD-L1 status are in the Table. Additional description of the pts with long-term survival, including updated safety data as well as 3-y OS by smoking history, histology, EGFRstatus, and prior radiation therapy, will be presented. Conclusions: Pembro provides promising long-term OS benefit for 1L and previously treated advanced NSCLC pts expressing PD-L1. The current data represent the longest efficacy and safety follow-up for pts with advanced NSCLC treated with pembro. Clinical trial information: NCT01295827

*Includes unknown PD-L1 status and TPS <1% pts.