Survival Comparisons for Breast Conserving Surgery and Mastectomy Revisited: Community Experience and the Role of Radiation Therapy.

OBJECTIVES Evidence suggests superiority of breast conserving surgery (BCS) plus radiation over mastectomy alone for treatment of early stage breast cancer. Whether the superiority of BCS plus radiation is related to the surgical approach itself or to the addition of adjuvant radiation therapy following BCS remains unclear. MATERIALS AND METHODS We conducted a retrospective cohort study of women with breast cancer diagnosed from 1994-2012. Data regarding patient and tumor characteristics and treatment specifics were captured electronically. Kaplan-Meier survival analyses were performed with inverse probability of treatment weighting to reduce selection bias effects in surgical assignment. RESULTS Data from 5335 women were included, of which two-thirds had BCS and one-third had mastectomy. Surgical decision trends changed over time with more women undergoing mastectomy in recent years. Women who underwent BCS versus mastectomy differed significantly regarding age, cancer stage/grade, adjuvant radiation, chemotherapy, and endocrine treatment. Overall survival was similar for BCS and mastectomy. When BCS plus radiation was compared to mastectomy alone, 3-, 5-, and 10-year overall survival was 96.5% vs 93.4%, 92.9% vs 88.3% and 80.9% vs 67.2%, respectively. CONCLUSION These analyses suggest that survival benefit is not related only to the surgery itself, but that the prognostic advantage of BCS plus radiation over mastectomy may also be related to the addition of adjuvant radiation therapy. This conclusion requires prospective confirmation in randomized trials.