Postmenopausal women with obesity who intentionally lost weight had a lower risk for endometrial cancer, according to results of the Women’s Health Initiative observational study.

“Many older adults think it’s too late to benefit from weight loss, or think that because they are overweight or obese, the damage has already been done, but our findings show that’s not true,” Juhua Luo, PhD, associate professor of epidemiology and biostatistics at Indiana University School of Public Health, said in a press release.

Luo and colleagues evaluated 36,794 postmenopausal women aged 50 to 79 years recruited from 40 clinical centers between September 1993 and December 1998. Weight was measured at enrollment and again at 3 years.

Weight change was categorized as stable (within ± 5%) or a loss or gain (more than 5% change). All incidences of endometrial cancer diagnosed after the 3-year visit served as the primary outcome of the study.

Over a mean follow-up of 11.4 years, 566 women were diagnosed with endometrial cancer.

Multivariate analyses adjusted for baseline BMI, age and menopausal hormone therapy showed that women who had lost more than 5% of weight had a 29% lower risk for endometrial cancer compared with women who had stable weight (HR = 0.71; 95% CI, 0.54-0.95).

When analyzed by baseline BMI, weight loss was associated with significantly lower endometrial cancer risk among women who had been obese (HR = 0.47; 95% CI, 0.29-0.77), but not among women who were overweight (HR = 1.16; 95% CI, 0.74-1.83) or normal weight (HR = 0.8; 95% CI, 0.47-1.35).

Women obese at baseline who intentionally lost weight had a greater risk reduction than women who unintentionally lost weight (intentional, HR = 0.44; 95% CI, 0.25-0.78; unintentional, HR = 0.57; 95% CI, 0.25-1.3). When measured in pounds rather than a percentage, the association persisted among obese women who intentionally lost weight (HR = 0.52; 95% CI, 0.3-0.9).

In a sensitivity analysis of weight loss and endometrial cancer subtypes, researchers observed a stronger association between intentional weight loss and risk for type I endometrial cancer compared with overall results (all women, HR = 0.48; 95% CI, 0.3-0.76; obese women, HR = 0.26; 95% CI, 0.12-0.57).

This study shows that weight loss even later in life is beneficial, according to Jennifer A. Ligibel, MD, ASCO expert in cancer prevention and director of the Leonard P. Zakim Center for Integrative Therapies at Dana-Farber Cancer Institute, who was not involved in the study.

“There have been more than a thousand studies linking obesity to an increased risk for endometrial and other cancers, but almost none that look at the relationship between weight loss and cancer risk,” Ligibel said in the press release. “This study tells us that weight loss, even later in life, is linked to a lower risk of endometrial cancer.”

The researchers would like to further examine the role of weight loss in other populations, according to the release.

“We’re interested to see whether weight loss plays a role in the prevention of other cancers that are linked to obesity, Luo said. “We already know that avoiding obesity is associated with many health benefits, but we do not know enough about the benefits of weight loss for adults who are already obese.” – by Melinda Stevens

Disclosures: Luo reports no relevant financial disclosures. Please see the full study for a list of all other researchers’ relevant financial disclosures.

Luo J, et al. J Clin Oncol. 2017;doi:10.1200/JCO.2016.70.5822.