Fox Chase Cancer Center researchers have unveiled promising interim results from their RETAIN-2 clinical trial, suggesting that a novel combination of chemotherapy and immunotherapy could improve outcomes for patients with muscle-invasive bladder cancer while preserving their bladders.
The phase II trial, presented at the 2025 American Society of Clinical Oncology (ASCO) Genitourinary Cancers Symposium in San Francisco, evaluated the effectiveness of combining four-drug chemotherapy (ddMVAC) with the immunotherapy agent nivolumab as neoadjuvant therapy.
Improved Treatment Outcomes
"Our goal with RETAIN is to help our patients preserve their bladders, if possible, while effectively treating muscle-invasive bladder cancer," explained Dr. Pooja Ghatalia, Associate Professor in the Department of Hematology/Oncology at Fox Chase Cancer Center and the trial's lead investigator. "With this second trial, we are finding that adding neoadjuvant immunotherapy may help us better achieve these aims."
The study, involving 71 patients, has shown encouraging results compared to its predecessor, RETAIN-1. In patients who underwent cystectomy, 40% showed no evidence of cancer post-surgery – a substantial improvement from the 15% complete response rate observed in RETAIN-1.
Current Treatment Landscape
Standard treatment for muscle-invasive bladder cancer typically involves chemotherapy followed by complete bladder removal (cystectomy). The RETAIN trials represent an effort to identify patients who might safely preserve their bladders while maintaining effective cancer control.
Trial Design and Interim Results
The RETAIN-2 protocol stratified patients into two groups based on specific clinical indicators: an active surveillance group who retained their bladders after neoadjuvant therapy, and a treatment group who proceeded with standard care including cystectomy.
While the trial's primary endpoint of two-year metastasis-free survival has not yet been reached for all participants, current data shows promising outcomes:
- 85% of the treatment group remains metastasis-free
- 82% of the active surveillance group shows no signs of metastasis
- 60% of active surveillance patients have successfully retained their bladders
"In the active surveillance patient group, who kept their bladder, we've seen less disease recurrence compared to the same group in RETAIN-1," noted Dr. Ghatalia. "This suggests that there is potential value in combining neoadjuvant chemotherapy with ddMVAC and immunotherapy for patients with bladder cancer regardless of whether they undergo active surveillance or cystectomy."
Clinical Implications
These interim findings suggest that the addition of immunotherapy to standard chemotherapy could provide a more effective bladder-preserving approach for suitable candidates with muscle-invasive bladder cancer. The higher complete response rates and promising metastasis-free survival data indicate potential for improving both quality of life and oncological outcomes for these patients.
