February 5, 2009

Adult Weight Change Influences Risk of Breast Cancer

Three recent studies have highlighted the benefits of maintaining a healthy weight throughout adulthood (this includes trying to lose the weight that you’ve already gained). The first study explores the effects of both weight gain and weight loss on risk of postmenopausal breast cancer; the second explores the effects of weight gain on particular types of breast cancer; and the third explores the effects of weight gain among women with a BRCA1 or BRCA2 mutation.

Adult Weight Changes and Breast Cancer Risk

Women with a higher body mass index (a comparison of weight to height) are known to have a higher risk of postmenopausal breast cancer. Furthermore, several studies have linked adult weight gain with an increased risk of breast cancer. Less is known, however, about whether weight loss can decrease risk or about the effects of weight change later in life (after the time of menopause).

To explore how adult weight change affects risk of breast cancer, researchers evaluated information from the Nurses’ Health Study.[1] The study included over 87,000 postmenopausal women who did not have cancer when the study began. They were followed for up to 26 years. Over the course of follow-up, more than 4,000 cases of breast cancer were diagnosed.

  • Women who gained 55 pounds or more after the age of 18 had a 45% increase in risk of breast cancer. The link between weight gain and breast cancer was particularly strong for women who had never used postmenopausal hormones.
  • Women who gained 22 pounds or more after menopause had an 18% increased risk of developing breast cancer.
  • Among women who had never used postmenopausal hormone therapy, weight loss after menopause was linked with a decreased risk of breast cancer. Women who lost 22 pounds or more and kept it off cut their risk of breast cancer by more than half.
  • Roughly 15% of the breast cancers in this population may be due to weight gain after the age of 18, and 4.4% may be due to weight gain since the time of menopause.

This study confirms that weight gain in adulthood, including weight gain after the time of menopause, increases the risk of breast cancer in postmenopausal women. Importantly, however, the study also suggests that weight loss may decrease risk for some women. The researchers point out that because weight loss can be difficult, the best approach is to maintain a healthy weight throughout adulthood.

Adult Weight Gain and Type and Stage of Breast Cancer

A second study evaluated the link between adult weight gain and type and stage of breast cancer.[2] The study involved 44,161 postmenopausal women, 1,200 of whom developed breast cancer. The study included only women who were not using postmenopausal hormones.

  • Women with the most weight gain in adulthood had increased risks of both ductal and lobular breast cancer. Compared to women who gained 20 or fewer pounds, women who gained more than 60 pounds were almost twice as likely to develop ductal carcinoma and roughly 50% more likely to develop lobular carcinoma.
  • Weight gain increased the risk of breast cancer of all stages and grades, but seemed to have the greatest impact on regional and distant disease. Compared to women with the least weight gain, women with the greatest weight gain were more than three times more likely to develop regional or distant breast cancer.

These results, like the previous study, suggest a link between adult weight gain and increased risk of postmenopausal breast cancer.

Weight Gain and BRCA1/2 Carriers

Finally, a third study explored the effect of weight gain among women at very high risk of breast cancer due to a BRCA1 or BRCA2 mutation.[3] Women who had gained the most weight in adulthood (after the age of 18) had a more than four-fold increase in breast cancer risk. Weight gain after the age of 30 was also linked with an increased risk. This suggests that the link between weight gain and breast cancer risk also applies to this very high-risk group of women.

These three studies provide additional motivation to maintain or to work towards a healthy body weight in adulthood. Furthermore, the results of the first study suggest that it’s never too late to start.

[1]Eliassen A, Colditz G, Rosner B, et al. Adult Weight Change and Risk of Postmenopausal Breast Cancer. Journal of the American Medical Association. 2006; 296:193-201.

[2]Feigelson HS, Patel AV, Teras LR, Gansler T, Thun MJ, Calle EE. Adult Weight Gain and Histopathologic Characteristics of Breast Cancer Among Postmenopausal Women. Cancer. Early Online Publication May 22, 2006.

[3]Nkondjock A, Robidoux A, Paredes Y, Narod SA, Ghadirian P. Diet, Lifestyle and BRCA-related Breast Cancer Risk among French-Canadians. Breast Cancer Research and Treatment. 2006;98:285-294.

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Tags: Breast Cancer, Uncategorized