391 Background: The standard of care (SOC) for patients (pts) with MIUC is radical surgery ± cisplatin-based neoadjuvant chemotherapy (chemo), but many pts are cisplatin-ineligible. There is no conclusive evidence supporting adjuvant chemo in pts who did not receive neoadjuvant chemo and in those with residual disease after neoadjuvant cisplatin. This phase 3 trial of adjuvant nivolumab (NIVO) vs placebo (PBO) in pts with MIUC after radical surgery ± neoadjuvant cisplatin (CheckMate 274) aims to address an unmet need in these pts. We report the initial results. Methods: This is a phase 3, randomized, double-blind, multicenter trial of NIVO vs PBO in pts with high-risk MIUC (bladder, ureter, or renal pelvis) after radical surgery. Pts were randomized 1:1 to NIVO 240 mg Q2W or PBO for ≤ 1 year of adjuvant treatment. Pts had radical surgery within 120 days ± neoadjuvant cisplatin or were ineligible/declined cisplatin-based chemo, evidence of UC at high risk of recurrence per pathologic staging, were disease-free by imaging, and ECOG PS ≤ 1. Primary endpoints: disease-free survival (DFS) in all randomized pts (ITT population) and in pts with tumor PD-L1 expression ≥ 1%. DFS was stratified by nodal status, prior neoadjuvant cisplatin, and PD-L1 status. Non–urothelial tract recurrence-free survival (NUTRFS) in ITT pts and in pts with PD-L ≥ 1% is a secondary endpoint. Safety is an exploratory endpoint. Results: In total, 353 pts were randomized to NIVO (PD-L1 ≥ 1%, n = 140) and 356 pts to PBO (PD-L1 ≥ 1%, n = 142). The primary endpoint of DFS was met in ITT pts (median follow-up, 20.9 mo for NIVO; 19.5 mo for PBO) and in pts with PD-L1 ≥ 1%. DFS and NUTRFS were improved with NIVO vs PBO in both populations (Table). DFS improvement with NIVO was generally consistent across subgroups. Grade 3–4 treatment-related adverse events (TRAEs) occurred in 17.9% and 7.2% of pts in the NIVO and PBO arms, respectively. Conclusions: NIVO demonstrated a statistically significant and clinically meaningful improvement in DFS vs PBO for MIUC after radical surgery, both in ITT pts and pts with PD-L1 ≥ 1%. AEs were manageable and consistent with previous reports. These results support adjuvant NIVO as a new SOC for pts with MIUC with high risk for recurrence despite neoadjuvant chemo or those ineligible for and/or declining cisplatin-based chemo. Clinical trial information: NCT02632409 . Research Sponsor: Bristol Myers Squibb[Table: see text]
462P A clinical nomogram and recursive partitioning analysis to determine five-year disease-free survival in patients with thoracic esophageal carcinoma after radical surgery