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ObesityWeek 2019

20 percent post-bariatric weight loss reduces cancer risk by half

Study compared differences in cancer risk reduction among weight-loss surgery patients

Patients with severe obesity who had bariatric surgery and lost more than 20% of their total weight were 50% less likely to develop cancer. compared to patients who did not have as much weight loss after surgery, according to a study presented today by Oregon Health & Science University researchers at the 36th American Society for Metabolic and Bariatric Surgery (ASMBS) Annual Meeting at ObesityWeek 2019.

Researchers reviewed data from 2,107 adults who underwent bariatric surgery (either laparoscopic gastric bypass or gastric banding), at hospitals participating in the LABS-2 (Longitudinal Assessment of Bariatric Surgery 2) study. The average age of patients was 46 years old, 79% were female, about a third had type 2 diabetes and 44% had a history of smoking before surgery. Weight and cancer serum biomarkers (proteins detected in the blood, urine or body tissues) were measured preoperatively and one year after surgery, as predictors for incident cancer after adjusting for age, sex, education, and smoking history.

While previous studies have shown that bariatric surgery reduces the risk of certain cancers compared to patients who do not have the surgery, this study compared the differences in risk based on the amount of weight lost after bariatric surgery.

Researchers found having a BMI>30 or more one year after bariatric surgery was suggestive of a 60% higher risk of cancer compared to having a BMI<30. About 6.2% of those that lost less than 20% of their body weight reported a cancer diagnosis by year 7, compared to about 3.6% of patients who lost 20% or more of their total body weight - representing a 50% reduction. Overall, the average BMI at 12-months after surgery was 33 and the average excess weight loss was 58%.

Andrea Stroud

The most common cancer type was breast cancer (34%), followed by thyroid (8.5%), melanoma (7%), colon (6%), kidney (6%), uterine (5%) and lung (4%). The incidence of bladder, cervical, prostate, brain, endometrial, oesophagus, stomach and testicular was less than 3%.

"Our data suggests that there is a weight loss threshold, that if achieved, significantly reduces risk of cancer in post- bariatric surgery patients," said lead study author, Dr Andrea M Stroud, Assistant Professor of Surgery, Division of Bariatric Surgery, Oregon Health & Science University School of Medicine in Portland. "So, there seems to be a variability in the protective effect of bariatric surgery that is dependent on the degree of weight loss."

Researchers also found that metabolic changes after bariatric surgery contributed to lowering the risk of cancer. For each 20% reduction in leptin, a hormone released from the fat cells located in adipose tissue, there was a 20% reduction in cancer incidence. Decreases in diabetes-related fasting glucose, proinsulin, insulin and C-peptide levels and increased levels of ghrelin, the hunger hormone, were also associated with reduced cancer risk.

"For people with severe obesity, bariatric surgery is the most effective treatment available and we're seeing more and more evidence that it's also an effective way to prevent a number of diseases including cancer, heart disease, and diabetes," said Dr Eric J DeMaria, President, ASMBS and Professor and Chief, Division of General/Bariatric Surgery, Brody School of Medicine, East Carolina University Greenville, NC, who was not involved in the study.

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