Bariatric surgery, or weight-loss surgery, is normally used as a last resort when all other efforts have failed for obese patients who need to lose weight for their health. And now, researchers have found that the weight loss following such surgery significantly reduces the risk of endometrial (uterine) cancer in women.
According to the US Centers for Disease Control and Prevention (CDC), uterine cancer is the fourth most common cancer in women. Though all women are at risk for this cancer, the risk increases with age, and most cases are found in women who have gone through menopause.
Researchers from the study, which is published in the April issue of the journal Gynecologic Oncology, note that obesity is a significant public health problem in the US.
The team, comprised of researchers from the University of California-San Diego (UCSD) and Moores Cancer Center, says around two thirds of adults in the US are overweight or obese. Though obesity is linked to a range of health risks, including heart disease, diabetes and cancer, it is also linked to cancer of the uterus in women.
To investigate these links in detail, the researchers analyzed a retrospective cohort study of over 7 million patients in the University HealthSystem Consortium database, which provides information from academic medical centers and affiliated hospitals in the US.
From this database, the researchers identified 103,797 patients with a history of bariatric surgery, and 44,345 had a diagnosis of uterine malignancy.
Dr. Kristy Ward, first author and senior gynecologic oncology fellow in the Department of Reproductive Medicine at UCSD School of Medicine, explains what they found:
"Estimating from various studies that looked at increasing body mass index (BMI) and endometrial cancer risk, a woman with a BMI of 40 would have approximately eight times greater risk of endometrial cancer than someone with a BMI of 25."
And she says that this risk will likely rise as BMI increases.
'Obesity may be a modifiable risk factor for uterine cancer'
Weight loss that comes as a result of bariatric surgery significantly reduces a woman's risk of uterine cancer, researchers say.
To qualify for bariatric surgery, patients must be defined as either severely obese with a BMI over 40, or they must have a BMI of 35 or greater alongside one related condition, such as diabetes, obstructive sleep apnea, obesity-related cardiomyopathy, heart muscle disease or severe joint disease.
The surgery involves either removing a portion of the stomach or resecting and routing the small intestines to a small stomach pouch.
Lifestyle changes following surgery are vital to ensuring long-term weight loss success, the team notes.
Though any type of surgery carries with it certain risks, the researchers report that bariatric surgery - followed by dramatic weight loss in women who were formerly obese - reduces risks of uterine cancer by 71%, up to as much as 81%, provided normal weight is maintained after the surgery.
The team says their findings suggest that obesity may be a modifiable risk factor for endometrial cancer, and that bariatric surgery may be a feasible option for patients who are eligible.
Endometrial cancers are estrogen-driven
There are several biological mechanisms that link obesity with endometrial cancer, the researchers say. For example, extra adipose or fat tissue raises estrogen levels, which is linked with the creation of tumors and metastasis.
- It is the most commonly diagnosed gynecological cancer.
- In 2010, 44,717 women in the US were diagnosed with uterine cancer.
- That same year, 8,402 women died from it.
Dr. Ward explains that most endometrial cancers are driven by estrogen.
"In a normal menstruating woman," she says, "two hormones control the endometrium (inner lining of the uterus). Estrogen builds up the endometrium and progesterone stabilizes it. A woman with excess adipose tissue has an increased level of estrogen because the fat tissue converts steroid hormones into a form of estrogen."
She adds that if there is too much estrogen, it causes the endometrium to further build up, and meanwhile there is not enough progesterone to stabilize it.
"The endometrium continues to grow and can undergo changes into abnormal tissue, leading to cancer," she concludes.
Bariatric surgery works to reduce the impact of these factors by normalizing hormone levels, reducing insulin resistance and allowing for increased physical activity and improved health.
"The obesity epidemic is a complicated problem," Dr. Ward says, adding:
"Further work is needed to define the role of bariatric surgery in cancer care and prevention, but we know that women with endometrial cancer are more likely to die of cardiovascular causes than they are of endometrial cancer."
She adds that overweight or obese patients should be counseled about losing weight, and some who meet the criteria should be referred to a bariatric program.