Weight loss reduces the risk of postmenopausal breast cancer

Postmenopausal women who lost weight in 3 years had a 12% decrease in breast cancer risk compared to women whose weight remained stable, according to an observational study published in Cancer.

"Obesity is associated with an increased risk of postmenopausal breast cancer" Rowan T. Chlebowski, MD, PhD, Researcher Professor at the Department of Medical Oncology and Therapeutic Research at the National Medical Center of Hope City, and his colleagues wrote. "Since about one-third of menopausal women are obese, obesity represents a common and potentially modifiable factor related to the evolution of breast cancer. However, it has not been established that weight loss in postmenopausal women decreases the incidence of breast cancer or breast cancer mortality. "

Chlebowski and colleagues used observational data from the Women's Health Initiative to assess associations between weight loss and postmenopausal breast cancer.

The analysis involved 61,335 postmenopausal women without prior breast cancer and without normal mammography. The researchers evaluated body weight, height, and BMI at the beginning and third years.

The researchers ranked weight variation in the stable category (variation less than 5%, n = 41,139), loss of 5% or more (n = 8,175) or gain of 5% or more (n = 12,021) .

During an average follow-up of 11.4 years, researchers observed 3,061 cases of breast cancer.

Mean time between 3-year weight determination and breast cancer diagnosis was 6.47 years (range, 0.005-17).

Women with weight loss had a significantly lower risk of breast cancer compared to women whose weight was stable (HR = 0.88, 95% CI: 0.78-0.98).

The association remained after adjustment for mammography (HR = 0.88, 95% CI: 0.78-0.99) and after taking into account the self-reported intentionality of weight loss.

Weight gain of 5% or more did not appear to be associated with breast cancer risk (HR = 1.02, 95% CI, 0.93 to 1.11). However, researchers found an increased risk of triple negative breast cancer in women with weight gain (HR = 1.54, 95% CI, 1.16-2.05).

"Our study indicates that a moderate to relatively short-term weight reduction was associated with a statistically significant reduction in the risk of breast cancer in postmenopausal women," Chlebowski said in a press release. "These are observational results, but they are also corroborated by evidence from randomized clinical trials derived from the Women's Health Initiative's modified diet trial." in which, in the context of randomized clinical trials, the adoption of a low-fat diet was associated with similar weight loss. resulted in a significant improvement in the overall survival of breast cancer. These findings, taken together, provide strong correlative evidence that a modest weight loss program can have an impact on breast cancer. "

The limitations of the study included measuring weight at the beginning and the third year only and the lack of biological justification for the association between weight gain and breast cancer. – by Cassie Homer

Disclosures: Chlebowski reports consulting roles with AstraZeneca, Novartis and Pfizer. The other authors do not report any relevant financial information.