Comparative Effectiveness Of Non-Cisplatin (Cis)-Based First-Line (1l) Regimens In Patients With Metastatic Urothelial Carcinoma (Muc): Veterans Affairs Control Cohorts Vs. Imvigor210.

496Background: For mUC patients (pts) ineligible for cis, 1L carboplatin (carbo)-based regimens and checkpoint inhibitors are recommended, but comparative data are lacking. We assessed OS in pts given 1L atezolizumab (atezo; anti–PD-L1) from Ph 2 study IMvigor210 and Veterans Affairs (VA) mUC pts treated with carbo standards. Methods: Carbo-based control cohorts were derived from the VA Health Care Network databases (diagnosed 2006-2017), with treatment (tx) defined per NCCN guidelines V2.2005. IMvigor210 eligibility criteria were used to refine non-cis VA cohorts. Prespecified OS predictors were balanced between VA and IMvigor210 pts using entropy (e)-balance weighting. OS was evaluated by Kaplan-Meier (KM) and Cox regression (weighted). Sensitivity analyses used stabilized inverse probability weighting (sIPW) and statistical adjustments. Results: Of 2056 VA pts included, 926 received carbo-based tx, of whom 380 received carbo+gemcitabine [CarboGem]; after IMvigor210 exclusion criteria, the carbo-based c...