918PAtezolizumab (atezo) vs chemotherapy (chemo) in patients (pts) with platinum-treated locally advanced or metastatic urothelial carcinoma (mUC): A long-term overall survival (OS) and safety update from the phase III IMvigor211 study

Abstract Background Atezo (anti–PD-L1) is approved for platinum-treated mUC and other indications. Here, we evaluated long-term OS and safety data from IMvigor211, a randomised study evaluating atezo monotherapy vs chemo in platinum-treated mUC (Powles Lancet 2018; primary analysis median follow-up: ≈ 17 mo). Methods Pts with disease progression during or following platinum-based chemo were assigned 1:1 to atezo 1200 mg or chemo (vinflunine, paclitaxel or docetaxel per investigator) IV q3w. OS (primary endpoint) and safety were evaluated descriptively in this ad hoc analysis. Results As of 8 Nov 2018, median follow-up was 34.3 mo. OS HRs were similar to those from the primary analysis. 24- and 30-mo OS rates were higher with atezo vs chemo in the intent-to-treat (ITT) and PD-L1 populations (Table). In ITT pts, OS HRs with atezo vs taxanes and vinflunine were 0.73 (95% CI: 0.59, 0.90) and 0.90 (95% CI: 0.74, 1.09), respectively. Grade 3-4 treatment-related adverse events (AEs) occurred in 22% of atezo-treated pts and 43% of chemo-treated pts (Grade 5 treatment-related AEs in 1% vs 2%, respectively). AEs leading to treatment discontinuation occurred in 9% of atezo-treated pts and 18% of chemo-treated pts. 11% of atezo-treated patients had a Grade 3-4 AE of special interest (vs 2% with chemo). 29% and 31% of pts in the atezo and chemo arms, respectively, received ≥ 1 subsequent non-protocol therapy; 8% in the chemo arm had non-protocol immunotherapy. Table:918P OS in IMvigor211 ITT and PD-L1 populationsPD-L1 IC2/3PD-L1 IC1/2/3ITTChemo n = 118Atezo n = 116Chemo n = 309Atezo n = 316Chemo n = 464Atezo n = 467Number of deaths (% of randomised pts)97 (82)85 (73)269 (87)261 (83)403 (87)386 (83)Median OS (95% CI), mo10.6 (8.4, 12.2)11.1 (8.6, 15.4)8.2 (7.4, 9.5)8.9 (8.2, 10.9)8.0 (7.2, 8.6)8.6 (7.8, 9.6)Stratified HR (95% CI)0.87 (0.64, 1.17)0.84 (0.70, 1.00)0.82 (0.71, 0.94)24-mo OS rate (95% CI)19%33%14%22%13%23%(12, 27)(24, 42)(10, 17)(18, 27)(10, 16)(19, 26)30-mo OS rate (95% CI)17%29%10%18%10%18%(10, 24)(21, 38)(7, 14)(14, 23)(7, 13)(15, 22)Data cutoff, 8 Nov 2018. Median follow-up, 34.3 mo (range: 0-42.3). Stratification factors: PD-L1 status on tumour-infiltrating immune cells (IC), chemo type, liver metastases, and number of prognostic risk factors. PD-L1 status on IC evaluated per VENTANA SP142 assay. Conclusions In this long-term update from IMvigor211, including 24- and 30-mo OS rates, continued OS benefit in favor of atezo vs chemo was observed in the IT