The RETAIN-1 and RETAIN-2 trials studied a new “risk-adapted” approach for treating muscle-invasive bladder cancer (MIBC). Instead of automatically removing the bladder with radical cystectomy, researchers wanted to find out which patients could safely keep their bladder through careful monitoring.
In this approach, patients first received chemotherapy (MVAC) combined with immunotherapy (nivolumab) before surgery. Their tumor tissue was tested for specific genetic changes linked to good response to treatment. After therapy, patients underwent detailed testing to check if any cancer remained. Those with no detectable disease and favorable biomarkers could enter active surveillance instead of having their bladder removed. A key tool was circulating tumor DNA (ctDNA) testing. If ctDNA was still detectable after treatment, patients had a much higher risk of cancer spreading, making it an important warning sign.
Results from RETAIN-2 were encouraging. In the overall group, the two-year metastasis-free survival rate was 70%. Among patients who entered active surveillance, the rate was 85%, and about 68% remained cancer-free with their bladder intact. These findings suggest that, for selected patients, careful monitoring after chemoimmunotherapy may allow them to avoid bladder removal without compromising cancer control.