Phase 1 Study of Chemoradiotherapy Combined with Nivolumab ± Ipilimumab for the Curative Treatment of Muscle-invasive Bladder Cancer

Background: Muscle-invasive bladder cancer (MIBC) has a poor prognosis. Chemoradiotherapy (CRT) in selected patients has comparable results to radical cystectomy. Results of neoadjuvant immune checkpoint inhibitors (ICIs) before radical cystectomy are promising. We hypothesize that ICI concurrent to CRT (iCRT) is safe and may improve treatment outcomes.

Objective: To determine the safety of iCRT for MIBC.

Design, setting, and participants: This multicenter, phase 1b, open-label, dose-escalation study determined the safety of CRT with three ICI regimens in patients with nonmetastatic (T2-4aN0-1) MIBC. Twenty-six patients received mitomycin C/capecitabine and 20 × 2.75 Gy to the bladder. Tolerability was evaluated in a cohort of up to ten patients. If two or fewer out of the first six patients or three or fewer of ten patients experienced dose-limiting toxicity (DLT), accrual continued in the next cohort.

Intervention: Patients received nivolumab 480 mg (NIVO480), nivolumab 3 mg/kg and ipilimumab 1 mg/kg (NIVO3 + IPI1), or nivolumab 1 mg/kg and ipilimumab 3 mg/kg (IPI3 + NIVO1).

Outcome measurements and statistical analysis: The primary endpoint was safety. Secondary objectives were response rate, disease-free survival, metastatic-free survival (MFS), and overall survival (OS).

Results and limitations: In the NIVO480 cohort, no patients experienced DLT. The NIVO3 + IPI1 2 patients experienced DLT, thrombocytopenia (grade 4), and asystole (grade 5). IPI3 + NIVO1 was discontinued after three out of six patients experienced DLT. Clinically significant adverse events (AEs) of grade ≥3 occurred in zero, three, and five patients in the NIVO480, NIVO3 + IPI1, and IPI3 + NIVO1 groups, respectively. The most common AEs were immune related and gastrointestinal. MFS and OS were 90% at 2 yr for NIVO480 and 90% at 1 yr for NIVO3 + IPI1. Limitations include the absence of a centralized pathology and radiology review, and a lack of biomarker analysis.

Conclusions: In this dose-finding study of iCRT, the regimens of nivolumab monotherapy and nivolumab 3 mg/kg with ipilimumab 1 mg/kg have acceptable toxicity.

Patient summary: We tested the safety of a new bladder-sparing treatment modality for muscle-invasive bladder cancer patients, combining immune checkpoint inhibitors simultaneously with chemoradiotherapy. We report that two regimens, nivolumab monotherapy and nivolumab 3 mg/kg with ipilimumab 1 mg/kg, are safe and can be used in phase 3 trials.