4526 Background: Approval of anti–PD-L1/anti–PD-1 CPI agents has changed the mUC tx landscape, but real-world (RW) tx patterns are not well described. Here, we describe pt characteristics, time on tx (TOT), tx-cycle distribution, relative dose intensity (RDI) and subsequent tx for pts receiving atezolizumab (atezo), nivolumab (nivo) or pembrolizumab (pembro) monotherapy. Methods: Pts diagnosed with mUC who completed atezo, nivo or pembro in the first-line (1L) or prior-platinum second-line and beyond (2L+) settings by April 30, 2018, were identified from the US-based Flatiron Health electronic health record–derived database. TOT was defined as time from first to last CPI administration + 1 cycle, tx cycles as number of CPI doses received during TOT and RDI as ratio of actual to planned dose per week to reflect any dose interruption. Results: RW data from pts receiving atezo, nivo and pembro were analyzed (Table). Up to 38% of pts had ECOG PS > 1. Median TOT ranged from 2.1-2.8 mo, with overlapping 95% CIs; mean TOT ranged from 2.7-4.1 mo. Over 50% of pts had ≤ 4 tx cycles. 21%-38% of pts did not have RDI within 95%-105% of the labeled dose. Most common subsequent txs were platinum-based chemotherapy combinations with gemcitabine or taxanes (post–1L CPI) and taxane monotherapy or other CPI monotherapy/combinations (post–2L+ CPI). Conclusions: Here, we present the largest analysis of RW CPI use in mUC to date. Overall, this unadjusted descriptive analysis showed relative comparability of pt and tx characteristics and TOT across CPI-treated groups. Insights into RW tx allow for an understanding of how clinical trial data translate to broader pt populations, including those with ECOG PS > 1, and may be useful for practitioners. [Table: see text]
800TiP Meet-URO 12: A randomized phase II trial of niraparib versus best supportive care (BSC) as maintenance treatment in patients with locally advanced or metastatic urothelial cancer (UC) whose disease did not progress after completion of first-line platinum-based chemotherapy