Pembrolizumab extends time to recurrence in aggressive bladder cancer

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Patients with muscle-invasive urothelial cancer and at high risk of recurrence after surgery may have a new treatment option. The Alliance for Clinical Trials in Oncology today announced positive results from the Phase III AMBASSADOR (A031501) trial for the adjuvant treatment of patients with localized muscle-invasive urothelial carcinoma (MIUC) and locally advanced urothelial carcinoma. Late-breaking data from the trial are being presented today during an oral abstract session at the 2024 American Society of Clinical Oncology (ASCO) Genitourinary (GU) Cancer Symposium (abstract #LBA531).

Patients with muscle-invasive bladder cancer are at high risk of disease recurrence and metastases after radical surgery. Pembrolizumab versus observation significantly reduced the risk of disease recurrence for these patients. “This is long-awaited data in the bladder cancer community.”

Andrea B. Apollo, MD, is study chair for the AMBASSADOR trial and chief of the Bladder Cancer Section of the Genitourinary Malignancies Branch and director of the Bladder Cancer and Genitourinary Tumor Multidisciplinary Clinic at the National Cancer Institute’s Center for Cancer Research.

In a pre-specified interim analysis review, pembrolizumab, an anti-PD-1 therapy, demonstrated a statistically significant and clinically meaningful improvement in disease-free survival (DFS) versus observation in patients after surgery, which met one of the trial’s dual primary endpoints. . . After a median follow-up of 22.3 months, pembrolizumab reduced the risk of DFS or death by 31% (HR=0.69). [95% confidence interval (CI), 0.55-0.87]; p=0.0013) vs observation of patients after surgery. Median DFS was 29.0 months (95% CI, 21.8—not evaluable). [NE]) for pembrolizumab and 14.0 months (95% CI, 9.7–20.2) for observation, an improvement of 15 months. These DFS results were consistent regardless of patients’ PD-L1 expression status. The trial’s other dual primary end point of overall survival (OS) did not reach statistical significance during this interim analysis and will continue to be followed as mature data (HR=0.98). [95% CI, 0.76-1.26]; p = 0.88). After a median follow-up of 36.9 months, median OS was 50.9 months (95% CI, 43.9-NE) for pembrolizumab versus 55.8 months (95% CI, 53.3-NE) for observation (HR=0.98). [95% CI, 0.76-1.26]; p = 0.88).

The safety profile of pembrolizumab in this trial was consistent with observations in previously reported studies and no new safety signals were identified. Grade 3+ adverse events (side effects that are serious or clinically significant but not immediately life-threatening) occurred in 48.4% of patients receiving pembrolizumab in 31.8% of patients under observation.

17.4% of patients receiving pembrolizumab withdrew from the trial without event, versus 27.2% from the observation arm. 76 patients (22%) in the observation arm subsequently received an immune checkpoint inhibitor.

AMBASSADOR (A031501) is a randomized, open-label phase III trial evaluating pembrolizumab versus observation for the adjuvant treatment of localized MIUC and locally advanced urothelial carcinoma. Dual primary endpoints are OS and DFS, and secondary endpoints include OS and DFS in PD-L1 positive and negative patients. The trial enrolled 702 patients who received pembrolizumab (200 mg intravenously every three weeks for up to 18 cycles) or underwent observation.

It is estimated that approximately 82,290 people in the United States will be diagnosed with bladder cancer in 2023. Globally, there were approximately 573,000 new cases and 212,000 deaths from bladder cancer in 2020. Muscle-invasive bladder cancer is cancer that has spread to bladder cancer, the muscle of the bladder wall, and locally advanced urothelial cancer is cancer that starts in urothelial cells and from where it has spread to nearby tissue or lymph nodes. Despite surgery, up to 50% of patients with bladder cancer recur within 12 months.

Ambassador is sponsored by the National Cancer Institute (NCI), part of the National Institutes of Health, and is administered and managed by the NCI-funded Alliance for Clinical Trials in Oncology with participation from the NCI-funded National Clinical Trials Network (NCTN) through a cooperative research and development agreement ( Part of Merck’s collaboration with NCI through CRADA). To learn more about the AMBASSADOR trial, visit

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