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What's New - Hormones and Breast Cancer

348 Portland-area women were involved in hormone study at Kaiser Permanente's Center for Health Research

Hormone Therapy Linked to More Advanced Breast Cancers, Later Diagnosis, and More Abnormal Mammograms

(PORTLAND, Ore.) - New findings from the Women's Health Initiative (WHI) show that use of combined estrogen plus progestin (E+P) hormone therapy is associated with an increased risk of breast cancer, diagnosis at a more advanced stage of breast cancer, and more abnormal mammograms. These findings appear in the June 25 issue of The Journal of the American Medical Association.

The original WHI study, involving more than 16,000 postmenopausal women nationwide and 348 Oregon and Southwest Washington women, was stopped early in July 2002 when it was found that the overall health risks of E+P, including breast cancer risk, exceeded the benefits. These new findings show that, compared with placebo, E+P increased total breast cancers (245 cases vs. 185 cases) and invasive breast cancers (199 cases vs. 150 cases). Invasive breast cancers among women taking E+P were larger and were diagnosed at a more advanced stage compared with those diagnosed among women taking a placebo. WHI researchers also found that, after one year, the percentage of women with abnormal mammograms was substantially greater in the E+P group (716 of 7,656 or 9.4 percent) than in the placebo group (398 of 7,310 or 5.4 percent). This difference in abnormal mammograms continued throughout the six years the women received mammograms.

Cheryl Ritenbaugh, PhD, principal investigator for the WHI clinical center at Kaiser Permanente's Center for Health Research, says, "For the past year, our advice has been that women should only take estrogen plus progestin for short-term relief of menopausal symptoms. That 'short-term' is now getting shorter. The changes in breast tissue due to taking combination hormone therapy appear within a year. These changes appear to both promote early breast cancers while making their detection harder. After four years, women who took E+P had a 45 percent greater risk of invasive breast cancer than women who took placebos."

Ritenbaugh adds that, "if a woman is on combination hormone therapy for relief of menopausal symptoms and gets even one abnormal mammogram, that should be a strong signal to seek alternatives."

Women in the WHI E+P study discontinued their use of E+P in July 2002. WHI researchers will be following these women to find out what happens to their breast cancer risk and the frequency of abnormal mammograms. Observational studies suggest that breast cancer risk will diminish over time.

A separate WHI study of the use of estrogen alone versus placebo involving 10,739 women who have had a hysterectomy is continuing. This arm of the study is scheduled to end in 2005. The E+P findings released in July 2002, last month (showing an increased risk of dementia), and this week don't apply to women who are taking estrogen alone. Women who are participating in the estrogen-alone study are asked to continue to take their study pills and to come for their regular clinic visits.

Kaiser Permanente's Center for Health Research, founded in 1964, is a non-profit research institute located in Portland, Oregon, and Honolulu, Hawaii. Its mission is to discover and advance knowledge to improve health.

Kaiser Permanente Northwest is a group practice health care organization serving the medical care needs of about 445,000 people in Oregon and Southwest Washington.

For more infomation contact:
Terry Fitzpatrick (503) 335-6602 or
Jim Gersbach (503) 831-4820

Released: June 24, 2003