Relationship between number of breast cancer operations performed and 5-year survival after treatment for early-stage breast cancer

Objectives. We examined the association between number of breast cancer operations performed in a hospital (hospital volume) and all-cause and breast cancer-specific mortality using a national database and statistical methods appropriate for clustering and reducing confounding. Methods. In a retrospective cohort study, we linked Surveillance, Epidemiology, and End Results tumor registry data with Medicare claims data. The cohort included 11225 Medicare patients who had undergone surgery for early-stage breast cancer from 1994 to 1996 in 457 different hospitals. Primary outcomes were all-cause and breast cancer-specific survival rates at a mean follow-up time of 62.5 months. Results. In comparison with treatment in a low-volume hospital, treatment in a high-volume hospital was associated with hazard ratios of 0.83 (95% confidence interval [CI] = 0.75, 0.92) for all-cause mortality and 0.80 (CI = 0.66, 0.97) for breast cancer-specific mortality. Conclusions. An association between the volume of breast cancer operations performed in a hospital and 5-year survival rates was observed for both all-cause and breast cancer-specific mortality. Further work investigating the aspects of hospital volume that contribute to increased survival is warranted.