2379P AVENANCE: Subgroup analysis of patients (pts) with advanced urothelial carcinoma (aUC) with histological variants from a real-world (RW) study of avelumab first-line maintenance (1LM)

≈10% of bladder cancers have nonpure UC histology; these tumors are often underdiagnosed and represent an unmet treatment need. AVENANCE (NCT04822350) is evaluating avelumab 1LM in pts with aUC in France and has previously shown clinical activity in a heterogenous population (N=593). We present a subgroup analysis of pts with histological variants. Eligible pts had aUC that had not progressed on 1L platinum-based chemotherapy (PBC) and previous, ongoing, or planned avelumab 1LM. The primary endpoint was overall survival (OS); secondary endpoints included progression-free survival (PFS), duration of treatment (DOT), and safety. Here, pts with nonpure UC (mixed UC with variants [UC-V] and pure variants [PV]) were analyzed. 44/593 pts had aUC with histological variants; at data cutoff (March 30, 2023), median follow-up was 18.0 mo (range, 12.9-20.4 mo). Tumor histology was UC-V, including micropapillary and epidermoid, in 32 pts (72.7%) and PV in 12 (27.3%). At the start of 1L PBC, most pts had metastatic disease (UC-V, 96.9%; PV, 91.7%) and ECOG PS 0/1 (UC-V, 71.4%; PV, 55.6%). The most common 1L PBC was gemcitabine + carboplatin in 65.6% of pts with UC-V and 75.0% with PV. In pts with UC-V and PV, best response to 1L PBC was complete response in 18.8% and 33.3%, partial response in 59.4% and 58.3%, and stable disease in 21.9% and 8.3%, respectively. In all 44 pts, median DOT was 5.1 mo (95% CI, 2.8-17.4 mo); 34.1% were still receiving treatment at data cutoff. The table shows OS, PFS, and safety data in pts with aUC with histological variants and the overall population. RW data from AVENANCE provide evidence of the effectiveness and safety of avelumab 1LM in pts with aUC, including histological variants. To our knowledge, this is the first analysis of avelumab 1LM in this pt population. Data are consistent with findings in the overall population.