Overall and Estrogen Receptor–Positive Breast Cancer Incidences Are Decreased Following Bariatric Surgery

Introduction Bariatric surgery treats morbid obesity resulting in long-lasting weight loss. Elevated body mass index (BMI) increases breast cancer risk. We hypothesized that patients undergoing bariatric surgery would have decreased overall and estrogen receptor (ER)-positive breast cancer incidences compared to a propensity-matched non-surgical cohort. Methods The bariatric population included all female patients who underwent weight loss surgery at a single institution from 1985 to 2015. Patients from all outpatient visits were propensity score matched 1:1 with bariatric patients using BMI, comorbidities, demographics, and insurance status. The primary outcome was breast cancer incidence. Univariate analyses compared the groups. Results A total of 4860 patients were included, with 2430 in both groups. Median follow-up time from date of surgery or morbid obesity diagnosis was 5.7 years. There were no differences in age or comorbidities aside from gastroesophageal reflux disease. Seventeen (0.7%) patients in the surgery group were subsequently diagnosed with breast cancer versus 32 (1.3%) in the non-surgery group ( p = 0.03). The non-surgery group had more ER-positive tumors [4 (36.4%) vs. 22 (71.0%); p = 0.04]. Conclusion Female patients who underwent bariatric surgery were less frequently diagnosed with any breast cancer and ER-positive breast cancer versus a propensity-matched cohort suggesting a possible oncologic benefit to weight loss surgery.