Real‐World Outcomes of Avelumab Maintenance Therapy in Patients With Curatively Unresectable Urothelial Carcinoma in Japan: Results From the Final Analysis of Postmarketing Surveillance

BACKGROUND: Avelumab maintenance therapy was approved in Japan in February 2021 for the treatment of curatively unresectable urothelial carcinoma (UC) that has not progressed after prior chemotherapy based on results from the JAVELIN Bladder 100 phase 3 trial. We report the final analysis of postmarketing surveillance (PMS) data on the safety and effectiveness of avelumab maintenance in clinical practice in Japan. METHODS: This prospective, multicenter, noninterventional PMS evaluated patients with curatively unresectable UC who received ≥ 1 dose of avelumab maintenance in Japan between February 2021 and December 2021. The observation period was ≤ 52 weeks in all patients. The primary objective was to evaluate the safety of avelumab maintenance based on the occurrence of prespecified adverse drug reactions (ADRs). The secondary objective was to evaluate effectiveness, including time to treatment failure (TTF), time to next-line treatment (TTNT), and overall survival (OS). RESULTS: Data were collected from 453 patients at 213 sites (data cutoff: March 6, 2024). Median age was 73 years, 90.3% had metastatic disease, and prior chemotherapy regimen was gemcitabine + cisplatin in 267 (58.9%), gemcitabine + carboplatin in 163 (36.0%), and others in 23 (5.1%). Any-grade prespecified ADRs occurred in 144 patients (31.8%), including grade ≥ 3 in 35 patients (7.7%). The most common any-grade prespecified ADRs were infusion reaction (11.7%) and thyroid dysfunction (7.3%). Median TTF was 4.6 months (95% CI, 3.8-5.3 months). Median TTNT was 9.9 months (95% CI, 8.3 months-not estimable). OS rates at 6 and 12 months were 89.2% (95% CI, 86.0%-91.8%) and 77.9% (95% CI, 73.7%-81.5%), respectively. CONCLUSION: Final analysis of PMS provides the largest real-world dataset of avelumab maintenance in Japan reported to date. Findings demonstrate the acceptable safety, tolerability, and effectiveness of avelumab maintenance, consistent with data from JAVELIN Bladder 100 and real-world studies in other countries, and support its continued use in clinical practice. TRIAL REGISTRATION: University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR): UMIN 43435.