Imvigor130 Clinical Trial In Patients (Pts) With Metastatic Urothelial Carcinoma (Muc): Analysis Of Upper Tract (Ut) And Lower Tract (Lt) Subgroups

551 Background: IMvigor130 demonstrated a statistically significant improvement in PFS in pts receiving atezolizumab (atezo; anti–PD-L1) + platinum-based chemotherapy (plt/gemcitabine [gem]; Arm A) vs placebo + plt/gem (Arm C) as first-line treatment for mUC (Grande et al. 2019). Exploratory analyses examined efficacy outcomes in UT and LT mUC subgroups. Methods: Pts with UT and LT mUC from Arm A and Arm C were included. Chemotherapy was gem + investigator choice of plt (cisplatin or carboplatin). Tumors were assessed at baseline and every 9 wk until investigator-assessed PD per RECIST 1.1 or other events. PFS, OS and ORR in UT and LT subgroups are shown. Results: Baseline characteristics were comparable between Arm A and Arm C in the UT and LT subgroups; however, slight imbalances were noted, such as higher PD-L1–positive status (IC2/3) and lower Bajorin risk score in UT Arm A pts. With a median follow-up of 11.8 mo, median PFS was8.2 vs 6.2 mo in Arm A vs Arm C in UT pts (HR, 0.69 [95% CI: 0.51, 0.94]) and 8.1 vs 6.5 mo, respectively, in LT pts (HR, 0.85 [95% CI: 0.70, 1.02]). Interim median OS was 16.9 vs 13.5 mo in Arm A vs Arm C in UT pts (HR, 0.78 [95% CI: 0.54, 1.12]) and 15.8 vs 13.4 mo, respectively, in LT pts (HR, 0.87 [95% CI: 0.70, 1.08]). See table for additional efficacy results. Conclusions: Exploratorysubgroup analyses suggest activity of atezo + plt/gem in both UT and LT mUC, with outcomes in UT pts comparable to those seen in the LT and ITT populations. Clinical trial information: NCT02807636. [Table: see text]