How bariatric surgery affects risk
Many cancers are associated with obesity, including endometrial, breast, colon, pancreas, gallbladder, and renal. Obesity is associated with increased conversion of androgens to estrogens in fat tissue, stimulating excessive endometrial proliferation and increasing the risk of endometrial hyperplasia and cancer. Bariatric surgery reliably causes sustained weight reduction. Multiple studies have reported that bariatric surgery reduces the risk of endometrial cancer.
Schauer and colleagues used data from the Kaiser Permanente health system to identify 22,198 obese people who had undergone bariatric surgery and 66,427 matched controls who were obese but did not have surgery.10 The study population was 81% female, with a mean age of 45 years and a mean BMI of 45 kg/m2. After an average 3.5 years of follow-up there were 2,542 incident cases of cancer, including 322 cases of endometrial cancer. Compared with conventional weight loss treatment, bariatric surgery reduced the risk of endometrial cancer by 50% (HR, 0.50; 95% CI, 0.37–0.67; P<.001).10 In addition, bariatric surgery reduced the risk of colon and pancreatic cancer by 41% and 54%, respectively.10
In the Swedish Obese Subjects (SOS) study, 1,420 women who underwent bariatric surgery and 1,447 matched controls who received conventional obesity treatment were followed for 18 years.11 At study entry, the mean age of the women was approximately 48 years, and the mean BMI was approximately 42 kg/m2. In follow-up there were 76 incident cases of endometrial cancer. Compared with women receiving conventional obesity treatment, women who had bariatric surgery had a non–statistically significant 49% decrease in the risk of developing endometrial cancer (HR, 0.51; 95% CI, 0.24–1.10)
In a systematic review of 5 additional studies (not including publications 10 or 11) of the impact of bariatric surgery on the risk of developing endometrial cancer, the surgery was associated with a 68% risk reduction (odds ratio [OR], 0.32; 95% CI, 0.16–0.63) compared with matched obese women that did not have surgery.12
Although there are no randomized prospective studies showing that bariatric surgery reduces the risk of endometrial cancer, the weight of the observation evidence is strong. In addition, bariatric surgery was reported to reduce all-cause mortality in the SOS study.13 Hence, for obese postmenopausal women, if lifestyle changes do not result in sustained weight loss, bariatric surgery may be an optimal approach to improving health outcomes.
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