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Bariatric Surgery May Help Protect Against Cancer in Obese Women

June 30, 2009 — Bariatric surgery may help protect against cancer in obese women, according to the results of a prospective, controlled intervention trial reported in the June 24 Online First issue of Lancet Oncology.

"Obesity is a risk factor for cancer," write Lars Sjöström, MD, from the University of Gothenburg in Gothenburg, Sweden, and colleagues from the Swedish Obese Subjects (SOS) study. Beginning in 1987, the SOS study enrolled 2010 obese patients who underwent bariatric surgery and 2037 contemporaneously matched obese control subjects who received standard treatment. Obesity was defined as a body mass index (BMI) of 34 kg/m² or more in men and 38 kg/m² or more in women. Although the primary outcome measure in SOS was overall mortality rate, the main endpoint of this analysis was incident cancer through December 31, 2005. Median follow-up duration was 10.9 years, with a cancer follow-up rate of 99.9%.

During the 10-year follow-up, mean weight loss was 20 kg in the bariatric surgery group vs a mean weight gain of 1.3 kg in the standard-care group. The number of first-time cancers after study enrollment was 117 in the surgery group, which was significantly lower than the standard-care group (n = 169; P = .0009).

When all cancer cases during the first 3 years of the intervention were excluded, the findings were similar. "Bariatric surgery was associated with reduced cancer incidence in obese women but not in obese men," the study authors write.

Limitations of this study include lack of randomization, slightly higher BMI and prevalence of some risk factors in the surgery group vs the control group, and the fact that cancer incidence was not a predefined endpoint of the SOS study.

"Earlier reports from SOS show that bariatric surgery is associated with reduced overall mortality, and has beneficial effects on diabetes, other cardiovascular risk factors, intima-media progression rate, cardiovascular symptoms, sleep apnoea, joint pain, and health-related quality of life," the study authors conclude. "The current exploratory report on cancer further underlines the favourable effects of bariatric surgery, particularly in women.

Lancet Oncol. Published online June 24, 2009.

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