Association between surgical case volume and survival in T1 bladder cancer: A plea for regionalization of care?

Abstract

Introduction: Prior research demonstrated an association between surgical case volume and survival in muscle-invasive bladder cancer (BC). This relationship, however, has not been investigated in the setting of T1 BC so far. Therefore, we investigated whether a higher surgical 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 and higher vs. below, median and higher 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 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]). Conclusions: This province-wide cohort study could demonstrate a volume-outcome relationship in T1 BC and raises questions regarding the regionalization of care in high-risk non-muscle-invasive BC. The generalizability of our findings, however, is limited by the fact that the performance of the initial resection by a high-volume surgeon does not necessarily translate into downstream care by the same surgeon.