Processes of care and the impact of surgical volumes on cancer-specific survival: a population-based study in bladder cancer.

OBJECTIVE: To describe the relationships between procedure volume and late survival after cystectomy for muscle-invasive bladder cancer (MIBC) and explore variables explaining any effect.
MATERIALS AND METHODS: Electronic records of treatment and surgical pathology reports were linked to a population-based registry to identify patients who underwent cystectomy during 1994-2008 in Ontario, Canada. Explanatory variables included adjuvant chemotherapy, lymph node dissection (LND), and margin status. A Cox proportional hazards regression model was used to explore associations between volume and cancer-specific survival (CSS) as well as overall survival.
RESULTS: The cohort included 2802 MIBC patients treated with cystectomy. High-volume hospitals were more likely to have used adjuvant chemotherapy (25% vs 18%; P <.001), more likely to have performed an LND (83% vs 53%; P <.001), and associated with a lower 90-day mortality (6% vs 10%; P = .032). Low-volume hospitals had a lower 5-year CSS rate of 32% (28%-36%) compared with those of high-volume centers at 38% (33%-42%). Individual surgeon volume was similarly associated with both early- and long-term outcomes. In multivariate analysis, both surgeon and hospital volumes were associated with CSS and overall survival. The surgeon volume effect on long-term outcomes was modestly modified by indicators of the quality of the LND, with little effect of the other explanatory variables.
CONCLUSION: Higher provider volume is associated with higher CSS in patients with MIBC in the general population. The volume effect was modestly mediated by the quality of LND.