A study by researchers at the University of California-San Diego finds that bariatric surgery in severely obese women may reduce the risk of uterine cancer by as much as 81 percent in those who maintain normal weight after surgery.
The study is based on more than 7.4 million patient records.
"Estimating from various studies that looked at increasing BMI and endometrial cancer risk, a woman with a Body Mass Index (BMI) of 40 would have approximately eight times greater risk of endometrial cancer than someone with a BMI of 25," said first author Kristy Ward, MD, the senior gynecologic oncology fellow in the Department of Reproductive Medicine at UC San Diego School of Medicine. "This risk likely continues to go up as BMI goes up."
Bariatric surgery involves reducing the size of the stomach using a gastric band, removing a portion of the stomach or resecting and re-routing the small intestines to a small stomach pouch. In all cases, the surgery must be followed by lifestyle changes to ensure long-term weight loss success.
Bariatric surgery is often the last resort for obese patients after all other non-surgical weight loss efforts have failed. To qualify, patients must be an acceptable surgical risk and be defined as either severely obese with a BMI of 40 or greater or have a BMI of 35 or greater with at least one related condition: diabetes, obstructive sleep apnea, obesity-related cardiomyopathy or heart muscle disease or severe joint disease.
What links obesity to uterine -- or endometrial -- cancer?
The researchers say that excessive fat tissue raises the levels of estrogen, which is associated with tumor creation. Obesity also causes chronic inflammation, boosting insulin resistance and increased estrogen levels.
"The majority of endometrial cancers are estrogen-driven," said Ward. "A woman with excess adipose tissue has an increased level of estrogen because the fat tissue converts steroid hormones into a form of estrogen.
"So there is too much estrogen, causing the endometrium to build up, but not enough progesterone to stabilize it. The endometrium continues to grow and can undergo changes into abnormal tissue, leading to cancer."
Obesity is a widespread public health problem in the United States, with an estimated two-thirds of the U.S. adult population considered to be overweight or obese. The condition is strongly linked to a host of health risks, among them heart disease, diabetes and cancer, in particular endometrial cancer.
Bariatric surgery has been shown to reduce the impact of these factors: hormone levels become normal; inflammation decreases; insulin resistance drops; weight loss allows for increased physical activity and improved overall health.
The study was published in the April issue of Gynecologic Oncology, the official publication of the Society of Gynecologic Oncology.