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.