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More Results from WHI on Breast Cancer Risk with Combined Hormone Therapy

Significantly more (and larger) breast cancers occurred among HT recipients than among placebo recipients in the WHI.

Previous results from the Women's Health Initiative (WHI) showed that increased risk for breast cancer was associated with combined estrogen and progesterone hormone therapy (HT; Journal Watch Jul 26 2002). Now, the WHI researchers present further details on breast cancer outcomes.

In the WHI, 16,608 women (age range, 50-79) without breast disease were randomized to daily conjugated equine estrogen (0.625 mg) plus medroxyprogesterone acetate (2.5 mg) or placebo; participants were followed for a mean of 5 years with annual mammography and breast exams.

Significantly more total breast cancers (245 vs. 185 cases; hazard ratio, 1.24) and invasive breast cancers (199 vs. 150 cases; HR, 1.24) were reported in the HT group than in the placebo group. A nonsignificant trend toward increased risk for in situ cancers also was noted (HR, 1.18). Invasive breast cancers in the HT group were significantly larger (1.7 vs. 1.5 cm), more likely to be node-positive (26% vs. 16%), and more likely to be diagnosed at an advanced stage (25% vs. 16% were regional or metastatic). In addition, abnormal mammograms were significantly more common in the HT group: 32% of hormone-treated participants had at least 1 abnormal mammogram during 5 years of follow-up, compared with 21% in the control group.

Comment: This analysis showed not only that breast cancer risk was higher in the HT group than in the placebo group but also that cancers often were diagnosed at more advanced stages in the HT group. Editorialists consider these results "as close to definitive as can be expected" regarding increased breast cancer risk with combined HT.

— Thomas L. Schwenk, MD

Published in Journal Watch General Medicine July 15, 2003

Citation(s):

Chlebowski RT et al. Influence of estrogen plus progestin on breast cancer and mammography in healthy postmenopausal women: The Women's Health Initiative randomized trial. JAMA 2003 Jun 25; 289:3243-53.

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• Medline abstract (Free)

Gann PH and Morrow M. Combined hormone therapy and breast cancer: A single-edged sword. JAMA 2003 Jun 25; 289:3304-6.

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• Medline abstract (Free)