Final analysis of KEYNOTE-189: Pemetrexed-platinum chemotherapy (chemo) with or without pembrolizumab (pembro) in patients (pts) with previously untreated metastatic nonsquamous non-small cell lung cancer (NSCLC).

9582 Background: The phase III KEYNOTE-189 study (NCT02578680), showed significant improvements in OS and PFS with pembro + chemo vs placebo + chemo in pts with previously untreated metastatic nonsquamous NSCLC without sensitizing EGFR/ALK mutations. We report the protocol-specified final analysis of KEYNOTE-189. Methods: Pts were randomized 2:1 to receive 35 cycles of pembro 200 mg Q3W (n = 410) or placebo Q3W (n = 206) plus 4 cycles of pemetrexed (pem) and carboplatin/cisplatin followed by maintenance pem. Pts in the placebo + chemo arm could crossover to pembro upon PD. PFS and OS were primary endpoints; ORR was a secondary endpoint. PFS2 (time from randomization to objective tumor progression on next-line treatment/death), was an exploratory endpoint. Results: At data cutoff (May 20, 2019), median (range) time from randomization to data cutoff was 31.0 (26.5–38.8) mo. 17 pts in the pembro + chemo arm and 1 pt in the placebo + chemo arm were receiving initially assigned treatment; 84 pts crossed over to pembro. Median (95% CI) OS (22.0 [19.5–24.5] vs 10.6 [8.7–13.6] mo; HR 0.56 [95% CI, 0.46–0.69]) and PFS (9.0 [8.1–10.4] vs 4.9 [4.7–5.5] mo; HR 0.49 [95% CI, 0.41–0.59]) were longer with pembro + chemo vs placebo + chemo (Table). The 2-y OS rate was 45.7% vs 27.3% and the 2-y PFS rate was 22.0% vs 3.4%. ORR was 48.3% with pembro + chemo vs 19.9% with placebo + chemo. 56 pts in the pembro + chemo arm completed 35 cycles of pembro among whom ORR was 85.7% (4 CR, 44 PR, 8 SD) and median OS was not reached. 292 (72.1%) pts in the pembro + chemo arm and 135 (66.8%) pts in the placebo + chemo arm had grade 3–5 AEs. Conclusions: Pembro + chemo continued to show improved outcomes in OS, PFS, ORR and PFS2 compared with placebo + chemo, with manageable toxicity. These findings support first-line pembro + chemo in pts with previously untreated metastatic nonsquamous NSCLC. Clinical trial information: NCT02578680 . [Table: see text]