Additional Research on Menopausal Hormone Therapy and Breast Cancer

A recent study of menopausal hormone therapy and risk of breast cancer reported that risk may vary by body weight and the type of hormone therapy. These results were published in Cancer Epidemiology, Biomarkers, & Prevention.

As women reach menopause and beyond, more than 80% will experience symptoms such as hot flashes, night sweats, sleep disturbance, and vaginal dryness. Estrogen, with or without progestin, is an effective treatment for many of these symptoms. Over the last several years, however, studies have raised important concerns about the health effects of menopausal hormone therapy.

Use of estrogen plus progestin has been linked with an increased risk of heart disease, breast cancer, stroke, and blood clots and a decreased risk of fractures and colorectal cancer. Use of estrogen alone, which is generally reserved for women who have had a hysterectomy, has been linked with an increased risk of strokes and a decreased risk of fractures.

Although it is now well established that menopausal hormone therapy with estrogen plus progestin increases the risk of breast cancer, researchers continue to explore the question of which subgroups of women are at greatest risk. This information would help personalize messages about the risks and benefits of hormone therapy.

The current study evaluated information from the California Teachers Study. Of the more than 56,000 perimenopausal or postmenopausal women in the study, 2,857 developed invasive breast cancer during 10 years of follow-up.

Compared with women who had never used hormone therapy, women who had used estrogen alone for 15 years or longer had a 19% increased risk of breast cancer (A 19% increase in risk means that if a woman has a 5% risk of getting breast cancer in the next 20 years, the risk goes up to 6%.). Women who had used estrogen plus progestin for 15 years or longer had an 83% increased risk of breast cancer (An 83% increase means that if a woman has a 5% risk over 20 years, the risk goes up to approximately 9%).For users of estrogen plus progestin, risk varied by the specific type of regimen used. Continuous regimens (progestin every day of the month) appeared to increase breast cancer risk to a greater extent than sequential regimens (progestin only some days of the month).The increased risk of breast cancer among users of hormone therapy was most apparent among thinner women.Use of hormone therapy increased the risk of cancers that were estrogen receptor-positive and progesterone receptor-positive.

These results provide additional evidence regarding the links between menopausal hormone therapy and risk of breast cancer. Women who are considering hormone therapy to manage menopausal symptoms are advised to talk with their doctor about the risks and benefits.

Reference: Saxena T, Lee E, Henderson K et al. Menopausal hormone therapy and subsequent risk of specific invasive breast cancer subtypes in the California Teachers Study. Cancer Epidemiology, Biomarkers, & Prevention [early online publication]. August 10, 2010.

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