Association between surgical case volume and survival in T1 bladder cancer: a need for centralization of care?

Introduction — Prior research demonstrated an association between surgeon case volume and survival in muscle-invasive bladder cancer (BC). This relationship, however, has not been investigated in the setting of high-risk, non-muscle-invasive BC (NMIBC). Hence, we investigated whether a higher surgeon case volume of T1 BC translates into improved survival outcomes.

Methods — Province-wide pathology reports (January 2002 to December 2015) were linked with health administrative data to identify patients diagnosed with T1 BC. For each patient, we determined the T1 case volume of the involved surgeon by benchmarking (percentile) her/him against his/her colleagues during a lookback period of one year. The volume-outcome (overall survival) relationship was then investigated by Cox proportional hazards regression (unadjusted and adjusted for a wide range of assumed confounders) that incorporated volume in three different ways (≥80th percentile vs. below, ≥ median vs. below, continuous [quintiles]). Effect sizes were presented as hazard ratios (95% confidence interval).

Results — We identified 7426 patients who were diagnosed with T1 BC and followed for a median of 4.8 years. A third of all patients (n=1895, 25.5%) received surgery by a high-volume surgeon (80th percentile and higher). Higher T1 case volume was associated with improved survival both in unadjusted (80th percentile: 0.93 [0.86– 0.99]; median: 0.93 [0.87–0.99]; continuous: 0.97 [0.94–0.99]) and adjusted analysis (80th percentile: 0.94 [0.88–1.01]; median: 0.93 [0.87–0.99]; continuous: 0.97 [0.95–0.99]) regardless of the method by which volume was analyzed.

Conclusions — This population-based cohort study demonstrated a volume-outcome relationship in T1 BC and raises questions regarding the centralization of care in high-risk NMIBC.