BARIATRIC surgery in females with obesity may reduce the risk of developing breast cancer to levels similar to those with a normal BMI, according to a retrospective matched cohort study. This suggests that “the carcinogenic associations between obesity and cancer risk are reversible and warrant public health attention given the current obesity crisis,” explained author Mehran Anvari, St. Joseph’s Healthcare, Hamilton, Ontario, Canada.
The study included nearly 70,000 females, divided evenly into five groups based on BMI category. In total, 13,852 underwent bariatric surgery and 55,408 did not. The groups were balanced for cancer history, age, and breast cancer screening stage, and were followed for 5 years. Breast cancers were diagnosed in 659 participants during the study period, including 103 in the surgical cohort. In the non-surgical cohort, there were 135 in the BMI≥35 group, 150 in the BMI 30–34 group, 143 in the BMI 25–29 group, and 128 in the BMI <25 group. The most commonly diagnosed cancers were Stage I, and the data did not show any significant differences for the distribution of grade, stage, or hormone status data across all cohorts. Researchers noted that after 1 year, there was no difference in incidence of breast cancer in those who had bariatric surgery, compared to those with a normal BMI; however, those who did not have surgery and had higher BMIs had a 25–42% risk for breast cancer, which was significantly higher than those who had surgery.
Researchers concluded that a significant proportion of females could reduce their breast cancer risk through weight loss surgery. They stated: “Given the increasingly strong evidence supporting a reduced risk of breast cancer after weight loss, even among women at high risk of breast cancer, breast cancer risk reduction should be discussed as a benefit of weight loss.” Limitations of the study included the inability to adjust for healthy user bias, as females in the surgical cohort may have been healthier than those in the non-surgical group, or may have made other lifestyle changes which impacted their breast cancer risk.