Avelumab maintenance therapy in patients (pts) with advanced urothelial carcinoma (UC) in Japan: Subgroup analyses by prior chemotherapy regimen from post-marketing surveillance (PMS).

692 Background: Avelumab was approved as maintenance therapy for pts with advanced UC that has not progressed after prior first-line platinum-based chemotherapy based on results from the JAVELIN Bladder 100 phase 3 trial, which showed a significant overall survival (OS) benefit. PMS data showed the safety and effectiveness of avelumab maintenance therapy in clinical practice in Japan. We report post hoc analyses of PMS data in subgroups defined by prior chemotherapy regimen. Methods: This prospective, multicenter, observational PMS evaluated pts with advanced UC who received ≥1 dose of avelumab between Feb and Dec 2021. The observation period was ≤52 weeks from start of avelumab in all pts. Data were analyzed in subgroups defined by prior chemotherapy for advanced UC: gemcitabine + cisplatin (GC), gemcitabine + carboplatin (GCa), or dose-dense methotrexate, vinblastine, doxorubicin, and cisplatin (ddMVAC). Pt characteristics were analyzed using descriptive statistics, and time-to-event analyses (from the start of avelumab maintenance therapy) used the Kaplan-Meier method. Results: The study cohort included 453 pts. Median age was 73 years (range, 21-91). Primary tumor site was bladder in 244 pts (53.9%) and upper tract in 209 (46.1%). Prior chemotherapy regimen was GC in 267 (58.9%), GCa in 163 (36.0%), and ddMVAC in 9 (2.0%). In chemotherapy subgroups, age was ≥75 years in 86 (32.2%), 89 (54.6%), and 1 (11.1%), and renal impairment was reported in 77 (28.8%), 82 (50.3%), and 2 (22%), respectively. At data cutoff (Mar 6, 2024), median duration of avelumab maintenance therapy was 5.1 mo (IQR, 2.3-12.0), 128 pts (28.3%) remained on avelumab, and 184 (40.6%) had received subsequent treatment. Prespecified adverse drug reactions (ADRs) of any grade were observed in 144 (31.8%) overall, and in 93 (34.8%) in the GC subgroup, 45 (27.6%) in the GCa subgroup, and 3 (33.3%) in the ddMVAC subgroup; ADRs were grade ≥3 in 36 (7.9%) overall, and in 22 (8.2%), 12 (7.4%), and 0 in subgroups, respectively. Median time to treatment failure was 4.6 mo (95% CI, 3.8-5.3) overall, and 4.6 mo (95% CI, 3.4-5.6), 4.6 mo (95% CI, 3.1-6.5), and 5.1 mo (95% CI, 1.4-11.8), in subgroups. Median OS was not reached in any subgroup; the 1-year OS rate was 77.9% (95% CI, 73.7-81.5) overall, and 79.6% (95% CI, 74.3-84.0), 73.8% (95% CI, 66.2-80.0), and 88.9% (95% CI, 43.3-98.4) in subgroups. Conclusions: This PMS represents the largest prospective observational study of avelumab maintenance therapy in pts with advanced UC in Asia. Post hoc analyses showed the acceptable safety and effectiveness of avelumab maintenance therapy in subgroups defined by prior chemotherapy regimen. Findings are consistent with analyses from JAVELIN Bladder 100 and support the favorable benefit-risk profile of avelumab in clinical practice in Japan, irrespective of prior chemotherapy regimen.