Impact of Facility Radiation Patient Volume on Overall Survival in Patients with Muscle Invasive Bladder Cancer Undergoing Trimodality Bladder Preservation Therapy

Background: There is an association between higher hospital and urologist case volume and improved survival outcomes for patients with bladder cancer. Less data on facility volume and outcomes exists following trimodality bladder preservation with TURBT followed by definitive chemoradiation (CRT). Materials and Methods: The National Cancer Database was queried for patients from 2004-2013 with urothelial bladder cancer (cT2-4aN0M0) receiving definitive CRT after TURBT. We compared OS between high- and low- bladder preservation case volume (BPCV) centers using Cox proportional hazard models. BPCV was dichotomized into high versus low volume at the 70th percentile level (i.e. high volume defined as top 30th percentile of cases and low volume defined as bottom 70th percentile of cases). Propensity matching was performed to match high- and low-volume centers. Results: A total of 666 treatment facilities treating 1,635 patients with bladder preservation were identified with a median follow-up of 26 months (range, 2-136 months). A 70th percentile cutoff identified 497 patients that received treatment at 64 high-volume facilities. Median OS of patients treated at high BPCV centers was 37.0 months (95% CI, 27.3-46.7) versus 32.3 months (95% CI, 27.9-33.6) for patients treated at low BPCV centers (P=0.004). High BPCV facilities were independently associated with a decreased hazard of death (HR, 0.86, 95% CI, 0.75-0.98; P=0.031). In the propensity score matched cohort, median OS of patients treated at high BPCV was 36.1 months (95% CI, 26.5-45.8) versus 28.1 months (95% CI, 23.9-32.3) for patients treated at a low BPCV facility (P=0.016). Conclusions: In this observational cohort, treatment at a high BPCV facility was associated with improved OS. Causal factors for this finding may include superior bladder specific clinician expertise, technology, and multidisciplinary-care.