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Background: In the global, phase 3 KEYNOTE-042 study, pembrolizumab (pembro) significantly prolonged OS vs chemotherapy (chemo) in patients (pts) with previously untreated advanced/metastatic NSCLC with PD-L1 TPS ≥1% without EGFR/ALK alterations. Among pts enrolled in China, pembro prolonged OS (HR; 95% CI) vs chemo in pts with PD-L1 TPS ≥50% (0.63; 0.43-0.94), TPS ≥20% (0.66; 0.47-0.92), and TPS ≥1% (0.67; 0.50-0.89). We present efficacy and safety outcomes with an additional 14 calendar mo of follow-up in Chinese pts in KEYNOTE-042. Methods: Pts enrolled in China in the KEYNOTE-042 global (NCT02220894) and China extension (NCT03850444) studies were randomized 1:1 to pembro 200 mg Q3W for ≤35 cycles or carboplatin+paclitaxel or pemetrexed with optional pemetrexed maintenance (nonsquamous only). Primary endpoints were OS in pts with PD-L1 TPS ≥50%, ≥20%, and ≥1%. Eligible pts who completed 35 cycles of pembro could receive a second course of pembro. No alpha was allocated to the China extension analysis. Results: 262 pts with PD-L1 TPS ≥1% were randomized in China to pembro (n = 128) or chemo (n = 134). Median time from randomization to data cutoff (Apr 28, 2021) was 47.2 (range, 39.8-56.1) mo. Pembro prolonged OS (HR, 95% CI) vs chemo in pts with PD-L1 TPS ≥50% (0.66, 0.45-0.95), ≥20% (0.68, 0.49-0.93), and ≥1% (0.67, 0.51-0.89; Table). 19.5% and 68.8% of pts in the pembro and chemo groups experienced treatment-related grade 3-5 AEs. Among 22 pts who completed 35 cycles of pembro, ORR was 81.8% (95% CI, 59.7%-94.8%); estimated OS rate 4 y after randomization was 69.1%. At data cutoff, 79 pts in each group had begun subsequent therapy; 4 pts began a second course of pembro. Conclusion: Similar to the global KEYNOTE-042 study, first-line pembro continues to prolong OS and provide durable response in pts in China with advanced/metastatic PD-L1-positive NSCLC without EGFR/ALK alterations after nearly 4 y of follow-up. Pembro monotherapy remains a standard of care in these pts. Table PD-L1 TPS ≥50% PD-L1 TPS ≥20% PD-L1 TPS ≥1% Pembro n = 72 Chemo n = 74 Pembro n = 101 Chemo n = 103 Pembro n = 128 Chemo n = 134 OS, median (95% CI), mo 24.5 (17.4-34.3) 13.8 (10.1-18.3) 21.9 (17.4-27.0) 13.5 (10.1-17.9) 20.2 (17.4-25.3) 13.5 (10.1-17.9) OS, HR (95% CI) 0.66 (0.45-0.95) 0.68 (0.49-0.93) 0.67 (0.51-0.89) OS 4-y rate (95% CI), % 23.4 (13.5-34.8) 13.6 (6.1-24.1) 22.5 (14.2-31.9) 14.4 (8.0-22.6) 21.3 (14.1-29.5) 12.7 (7.2-19.7) ORRa (95% CI), % 41.7 (30.2-53.9) 24.3 (15.1-35.7) 34.7 (25.5-44.8) 24.3 (16.4-33.7) 32.0 (24.1-40.9) 24.6 (17.6-32.8) DOR, median (range), mo 16.5 (1.4+ to 47.1+) 11.7 (1.6+ to 46.9+) 16.5 (1.4+ to 47.1+) 10.9 (1.6+ to 46.9+) 16.0 (1.4+ to 47.1+) 10.9 (1.1+ to 46.9+) DOR ≥2-y, % 36.9 34.0 37.4 25.6 36.7 25.0 DOR, duration of response; HR, hazard ratio; TPS, tumor proportion score. ‘+’ indicates no PD by time of last assessment. aPer RECIST v1.1 by blinded independent central review. Citation Format: Yi-Long Wu, Yun Fan, JianYing Zhou, Li Zhang, Qing Zhou, Wei Li, ChengPing Hu, GongYan Chen, Xin Zhang, CaiCun Zhou, Carmen González Arenas, Wei Fu, Helen Wu, Tony Mok. Pembrolizumab vs chemotherapy in Chinese patients with PD-L1-positive NSCLC: 4-year update from KEYNOTE-042 China study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT555.