Postmenopausal women who intentionally lost weight over the course of three years had a much lower risk of endometrial cancer up to 11 years later compared to women whose weight didn't change, a U.S. study finds.
Overall, women who intentionally lost 5 percent or more of their body weight had 29 percent lower risk of developing endometrial cancer during the study period, and the effect was most pronounced for obese women, whose risk dropped by 66 percent with weight loss.
"We decided to do the study because we realized that, although obesity increases the risk of endometrial cancer, research couldn't say if intentional weight loss, especially among older persons, could reduce that risk," lead author Juhua Luo, of the School of Public Health at Indiana University in Bloomington, told Reuters health in an email.
Endometrial cancer is the most common gynecologic cancer in the U.S. and the fourth most common cancer among women. About 2.8 percent of American women will be diagnosed with endometrial cancer at some point during their lifetime, according to the National Cancer Institute.
Body fat is thought to increase risk of this hormone-sensitive cancer by increasing the amount of estrogen a woman produces, the researchers write in Journal of Clinical Oncology.
For their study, Luo and her colleagues analyzed data on more than 36,000 women between the ages of 50 and 79 who participated in the larger, long-term Women's Health Initiative study.
All the women were weighed at the beginning of the study period and again three years later when they were also asked if they had intentionally tried to lose weight in the previous few years. The study team followed the women for an average of 11 more years and found that 566 women were diagnosed with endometrial cancer during that time.
With women whose weight remained stable as the reference point, researchers found that women who dropped pounds were significantly less likely to develop endometrial cancer, and those who gained weight saw an 8 percent to 23 percent increase in risk. For women who had not used hormone replacement therapy for menopausal symptoms and gained weight, risk rose by 30 percent.
"It is not too late to lose weight to reduce cancer risk, even if you are older," Luo said.
The study only looked at older women, but Luo said she thinks it is reasonable to think the effects might apply to younger women too, and more research is indicated.
"The majority of women with endometrial cancer are diagnosed with early-stage tumors that are associated with a high cure rate. However, despite this paradigm, not only is the incidence of endometrial cancer increasing, but the number of women who die as a result of the disease also is increasing," Dr. Jason Wright, chief of gynecologic oncology at Columbia University College of Physicians and Surgeons and New York Presbyterian Hospital, writes in an editorial accompanying the study.
In 2016, the number of deaths from endometrial cancer in the United States reached 10,170, which is a 25 percent increase compared with just five years earlier, he writes.
Luo's findings suggest that weight loss, even by a modest amount, can lower a woman's risk of endometrial cancer, Wright told Reuters Health by email.
"Fatty tissue releases estrogen which can stimulate the endometrium and increase a woman's risk of endometrial cancer," Wright said.
At present, the only women for whom screening is recommended are those with Lynch syndrome, a genetic abnormality that predisposes women to the development of endometrial and colorectal cancer among other cancer types, Wright noted.
"Most endometrial cancers will have symptoms early such as vaginal bleeding. Women with vaginal bleeding should consult with their physician for evaluation," he said.