The Effect of Hospital Volume on Breast Cancer Mortality

Objective: The aim of this study was to determine whether hospital volume was associated with mortality in breast cancer, and what thresholds of case volume impacted survival. Background: Prior literature has demonstrated improved survival with treatment at high volume centers among less common cancers requiring technically complex surgery. Methods: All adults (18 to 90 years) with stages 0-III unilateral breast cancer diagnosed from 2004 to 2012 were identified from the American College of Surgeons National Cancer Data Base (NCDB). A multivariable Cox proportional hazards model with restricted cubic splines was used to examine the association of annual hospital volume and overall survival, after adjusting for measured covariates. Intergroup comparisons of patient and treatment characteristics were conducted with X-2 and analysis of variance (ANOVA). The log-rank test was used to test survival differences between groups. A multivariable Cox proportional hazards model was used to estimate hazard ratios (HRs) associated with each volume group. Results: One million sixty-four thousand two hundred and fifty-one patients met inclusion criteria. The median age of the sample was 60 (interquartile range 50 to 70). Hospitals were categorized into 3 groups using restricted cubic spline analysis: low-volume (<148cases/year), moderate-volume (148 to 298cases/year), and high-volume (>298cases/year). Treatment at high volume centers was associated with an 11% reduction in overall mortality for all patients (HR 0.89); those with stage 0-I, ER+/PR+ or ER+/PR- breast cancers derived the greatest benefit. Conclusions: Treatment at high volume centers is associated with improved survival for breast cancer patients regardless of stage. High case volume could serve as a proxy for the institutional infrastructure required to deliver complex multidisciplinary breast cancer treatment.