Nonrandomized controlled trial of breast cancer risk after bariatric surgery and influence of insulin levels

Obesity and hyperinsulemia are risk factors for breast cancer, and retrospective studie suggest bariatric surgery reduces breast cancer risk in women. However, long-term prospective data on breast cancer risk after bariatric surgery and the role of baseline insulin levels are lacking. A secondary analysis of the prospective Swedish Obese Subjects Study, including 2867 women with obesity and a median follow-up of 23.9 years, found that bariatric surgery was associated with lower incidence of breast cancer compared to usual obesity care. The association between bariatric surgery and reduced risk was greatest in women with high levels of insulin at baseline. The authors conclude that bariatric surgery may protect against development of breast cancer in women with obesity, and insulin levels may help predict treatment benefit.