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Intentional weight loss lowers risk for endometrial cancer in postmenopausal women
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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.
Perspective
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Strengths of the study by Luo and colleagues include a large study population, sufficient follow-up time for cancer to develop, and measured rather than self-reported weight at two time points 3 years apart.
Key findings include that postmenopausal women who gained 10 or more pounds had 25% increased endometrial cancer risk, which is not surprising as overweight and obesity have been strongly and consistently associated with endometrial cancer in many prior reports. On the contrary, women who lost 10 or more pounds had a 30% lower risk. Yet, weight loss may be purposeful or unintended — which can be due to pre-existing illness — and this may influence morbidity and mortality.
When researchers separated weight loss by intent, 40% reduced risk was evident only with intentional loss of 10 or more pounds or 5% or more of body weight. Additional analyses indicated that these findings were strongest among obese women, women with estrogen plus progestin hormone therapy use, and women with estrogen-dependent type I endometrial cancers.
Potential limitations of this study include that results may not be generalizable to premenopausal women and that weight change was only assessed over 3 years. Undocumented weight change during additional follow-up could have resulted in exposure misclassification, and as there are more than two exposure levels, the resulting bias is not necessarily toward the null. Further, the number of endometrial cancer cases with intentional weight loss was modest (by pounds, n = 27; by percentage, n = 33), and so even within this large study, stratified analyses may be limited. In addition, the choice to combine women with stable but high BMI with those who increased from low to high BMI in some analyses merits comment, as risk may not be similar across these exposures.
Overall, results from this interesting and note-worthy study indicate that intentional weight loss can significantly lower endometrial cancer risk; this agrees with a growing body of literature that shows that even modest weight loss can positively impact human health and disease. For example, metabolic control and cardiovascular risk factor profiles improved among patients with diabetes, and hepatosteatosis of nonalcoholic fatty liver disease was markedly reduced in conjunction with 3% to 5% weight loss. Given that large changes can be very difficult to achieve and maintain, a shift from weight loss efforts to simply making healthier choices may be an important focus to integrate into public health messages, interventions and health care.
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