Atezolizumab in Combination With Gemcitabine and Cisplatin as First-Line Treatment in Metastatic Urothelial Cancer: A Randomized Phase II Study of Two Alternative Dosing Schedules

The potential impact of treatment sequencing in chemoimmunotherapy combinations remains underexplored. We evaluated 2 alternative dosing schedules of chemotherapy (cisplatin and gemcitabine [GC]) and an immune checkpoint inhibitor (CPI; atezolizumab [A]) for metastatic urothelial carcinoma (mUC).

This multicenter phase II study randomized cisplatin-eligible patients with previously untreated mUC in a 1:1 ratio. The chemo-first schedule included 2 cycles of GC, followed by 4 cycles of GC + A and A maintenance. The CPI-first schedule originally included a two-cycle A lead-in, later amended to a one-cycle lead-in, followed by 6 cycles of GC + A and A maintenance. The primary endpoint was objective response rate after the protocol amendment. Secondary endpoints included progression-free survival, overall survival, and safety.

Overall, 31 patients were randomized between 9/2017 and 2/2021 (chemo-first, n = 15; CPI-first, n = 16), with early discontinuation due to the evolving mUC management paradigm. Among the per-protocol evaluable patients (n = 19), ORR was 44% (95% CI, 14%-79%) in the chemo-first schedule and 40% (95% CI, 12%-74%) in the CPI-first amended schedule, with neither arm meeting the predefined efficacy threshold. Median follow-up was 60 months (95% CI 48-not reached [NR]). Median progression-free survival and overall survival (95% CI) were: chemo-first, 6.1 (4.4-NR) and 15 (10-NR) months; CPI-first original, 1.3 (1.1-NR) and 12 (8.4-NR) months; and CPI-first amended, 7.6 (2.0-NR) and 26 (3.6-NR) months. No new safety signals or treatment-related deaths occurred.

This study evaluating the impact of chemotherapy and CPI dosing sequence in patients with mUC was limited by a small sample size and early discontinuation, with neither arm meeting the primary endpoint. Exploratory observations highlight CPI lead-in duration as a potential consideration for future trial design.