Effect of Bacille Calmette-Guérin for Non–Muscle-Invasive Bladder Cancer After Prostate Radiotherapy

BACKGROUND: Little is known about the impact of prior prostate radiation therapy (RT) on the Bacille Calmette-Guerin (BCG) immunotherapy response in patients with non-muscle invasive bladder cancer (NMIBC). OBJECTIVE: We hypothesized that the damaging radiation effects on the bladder could negatively influence BCG efficacy. METHODS: Men with a history of high-risk NMIBC were identified within the Surveillance, Epidemiology, and End Results–Medicare database. All patients completed adequate BCG defined as at least 5 plus 2 treatments completed within 12 months. Patients were stratified into 2 groups: with prior RT for prostate cancer and without prior RT before the diagnosis of NMIBC. The primary endpoint was a 5-year composite for progression defined as disease progression requiring systemic chemotherapy, checkpoint inhibitors, radical or partial cystectomy, or cancer-specific death. RESULTS: We identified 3,466 patients with NMIBC, including 145 with prior RT for prostate cancer. Five-year progression occurred in 471 patients (13.6%). Patients with prior RT were older than patients without prior RT (77.0 vs 75.0 years; P < .001). The distribution of T stage was significantly different at diagnosis between the RT and non-RT groups (RT: Ta, 44.8%; Tis, 18.6%; T1, 36.6%; without RT: Ta, 40.9%; Tis, 10.8%; T1, 48.3%; P = .002). No difference in the risk of total progression was observed between patients with and without prior RT (P = .67). Similarly, no difference was observed after multivariable adjustment (hazard ratio, 0.99; 95% CI, 0.61-1.58; P = .95). CONCLUSION: For patients with NMIBC who undergo adequate BCG treatment, prior RT for prostate cancer was not associated with worse 5-year progression-free survival.