Obesity linked to all types of breast cancer

The greater the weight gain, the greater the risk for all types, stages and grades of breast cancer.

Issue: July 1, 2006

Women who gain weight in adulthood face a higher lifetime risk of all types of breast cancer even if they do not take hormone therapy after menopause.

A recent study found that the greater the weight gain as an adult, the greater the risk for all histological types, tumor stages and grades of breast cancer, particularly advanced malignancies. The most extremely obese women were up to three times more likely to have regional or distant metastases than women with less weight gain.

Circulating estrogen

Breast cancer risk is linked to increased lifetime levels of circulating estrogen. Fat tissue increases circulating estrogen, thereby, adding to the risk. Previous studies have shown, however, that the risk can be affected by other factors. Postmenopausal women who take hormone therapy actually mitigate the effects of obesity on cancer risk. Moreover, current weight as defined by body mass index is not as important as a woman’s weight gain after age 18.

While there is much literature on the risk of obesity and breast cancer, there are no data on whether that risk is specific for the type of breast cancer. Heather Spencer Feigelson, PhD, MPH, of the American Cancer Society, and colleagues investigated the risk between weight gain and type of invasive breast cancer among 44,161 postmenopausal women enrolled in the American Cancer Society’s Cancer Prevention Study II Nutrition Cohort who were not taking hormone therapy.

Increased risk

The researchers found that the greater the weight gain, the greater the risk for all types, stages and grades of breast cancer. Compared to women who gained 20 pounds or less during adulthood, women who gained more than 60 pounds were almost twice as likely to have ductal type tumors and were 1.5 times more likely to have lobular type cancers.

Risk for metastatic disease increased for all women who gained weight, with the risk greater than threefold for women who gained more than 60 pounds. As expected, weight gain increased the risk of estrogen receptor positive tumors, but not tumors that did not present estrogen receptors.

“These data further illustrate the relationship between adult weight gain and breast cancer, and the importance of maintaining a healthy body weight throughout adulthood,” Feigelson and colleagues said in Cancer. – by Judith Rusk

For more information:

Feigelson HS, Patel AV, Teras LR, et al. Adult weight gain and histopathologic characteristics of breast cancer among postmenopausal women. Cancer. In press.