Breast-conserving surgery (BCS) provides equivalent survival outcomes to unilateral mastectomy. There is no survival advantage to bilateral mastectomy in average risk breast cancer. Among a cohort of breast cancer patients expected to be candidates for BCS, we examined choice of surgery and factors associated with it. A prospective cohort study of unilateral clinical Stage I breast cancer patients treated at National Comprehensive Cancer Network centers from 2000 to 2009 was performed. The proportion of patients who initially underwent mastectomy versus BCS and time to definitive surgery and chemotherapy were examined. Of 10,249 patients, 23 % underwent mastectomy as an initial surgery. No decline in the use of mastectomy as initial surgery was found. There was significant institutional variation, with rates of initial mastectomy ranging from 14 to 30 % (adjusted odds ratio: 0.42-1.38). Tumor characteristics were associated with surgical option, but with small absolute differences. Of those who received initial mastectomy, 22 % had bilateral mastectomy, with an increase over time (2000:13 % vs. 2009:30 %) and substantial institutional variation (11-34 %). Women treated with initial mastectomy had longer median times from diagnosis to complete definitive surgery (6 vs. 4 weeks) and to start of adjuvant chemotherapy (12 vs. 11 weeks). Among Stage I breast cancer, the overall use of mastectomy did not change significantly over 10 years; however, an increasing proportion of women with unilateral cancer had bilateral mastectomy, and there was wide variation in type of surgery by institution. Further studies to assess reasons for the observed wide variation are warranted.
Keywords: Bilateral mastectomy; Breast cancer; Breast-conserving surgery; Mastectomy; Patterns of care; Stage I.