Phase II Trial of Risk-Enabled Therapy After Neoadjuvant Chemotherapy for Muscle-Invasive Bladder Cancer (RETAIN 1)

Cisplatin-based neoadjuvant chemotherapy (NAC) followed by cystectomy is the standard of care for patients with muscle-invasive bladder cancer (MIBC). Mutations in DNA damage repair genes are associated with pathologic downstaging after NAC. We hypothesized that a combination of biomarker selection and clinical staging would identify patients for cystectomy-sparing active surveillance (AS).

We conducted a single-arm, phase II, noninferiority trial to evaluate a risk-adapted approach for MIBC. Patients with cT2-T3N0M0 MIBC underwent NAC with accelerated methotrexate, vinblastine, doxorubicin, and cisplatin (AMVAC). Pre-NAC transurethral bladder tumor specimens were sequenced for mutations in ATM, ERCC2, FANCC, and RB1. Patients with ≥1 mutation and cT0 post-NAC began AS. The primary end point was metastasis-free survival (MFS) at 2 years for the entire cohort with the null hypothesis rejected if the lower bound exact one-sided 95% CI exceeds 64%.

Seventy patients were enrolled, 33 (47%) had a mutation, and 25 (36%) began per-protocol AS. With a median follow-up of 40 months, the 2-year MFS for all patients was 72.9% (lower bound exact one-sided 95% CI, 62.8). The 2-year MFS was 76.0% in the AS group (95% CI, 54.2 to 88.4) and 71.1% (95% CI, 55.5 to 82.1) in the remaining patients. In the AS group, 17 patients (68%) had some recurrence and 12 (48%) were metastasis-free with an intact bladder. The 2-year overall survival (OS) was 84.3% (95% CI, 73.4 to 91.0); OS was 88.0% (95% CI, 67.3 to 96.0) and 82.2% (95% CI, 67.6 to 90.7) in the AS and not-AS groups, respectively.

Patients with MIBC treated with AMVAC followed by a risk-adapted approach to local consolidation achieved a 2-year MFS rate of 73%. The primary end point was not met, but 17% of all enrolled patients and 48% of the AS group avoided cystectomy without metastatic disease.