Partial Nephrectomy Drives the Association Between High-volume Centers and Decreased Mortality: A Surveillance, Epidemiology, and End Results-Medicare Analysis.

OBJECTIVE: To better understand the association between high-volume surgical kidney cancer centers and decreased mortality. To identify quality metrics that mediate this association. METHODS: We designed a cohort of 14,044 patients who were diagnosed with kidney cancer between 2004 and 2013 and underwent a partial or radical nephrectomy using SEER-Medicare data. Hospitals were divided into quartiles based on their total nephrectomy volume for the study period. We investigated 6 quality metrics as potential mediators of the association between hospital volume and mortality using a mediation model. RESULTS: At the highest volume centers, survival was higher at 1-, 3-, 5-, and 10-year time intervals, respectively (91% vs 89%, 80% vs 76%, 70% vs 66%, 45% vs 38%, P < .001) compared to the lowest quartile nephrectomy centers. Receipt of partial nephrectomy for stage ≤T1a tumors explains 52.3% of the total association between hospital nephrectomy volume and mortality. Additionally, patients at the highest-volume centers were more likely to be younger (20% vs 26% 80≤ years old, P < .001), white (82% vs 78%, P < .001), reside in more densely populated counties (≥1 million residents, 62% vs 42%, P > .001), have a shorter mean length of stay (5.03 vs 5.88days, P < .001) when compared to those in the lowest-volume quartile. CONCLUSION: This analysis of SEER-Medicare data is the first to suggest that partial nephrectomy in the setting of T1a tumors mediates the association between hospital volume and mortality. Quality metrics that reduce mortality should be harnessed to develop more efficient and higher-quality health systems.