Estrogen-Progestin Hormone Therapy and Breast Cancer

Andrew M. Kaunitz, MD


October 21, 2010

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Hello. I'm Andrew Kaunitz, Professor and Associate Chairman, Department of OB/GYN, University of Florida College of Medicine in Jacksonville. Today I'd like to discuss new data from the Women's Health Initiative (WHI) concerning the use of estrogen-progestin hormone therapy (HT) and risk for mortality from breast cancer.[1]

Initial findings of the WHI randomized trial of estrogen-progestin therapy indicated a small increased risk for invasive breast cancer, which appeared limited to women who had used HT longer than 5 years.[2] Now, with a total mean follow-up of 11 years, WHI investigators report on breast cancer mortality in women who participated in the estrogen-progestin randomized clinical trial.

Although the histology of breast cancers was similar in the HT and placebo groups, tumors in women randomized to combination HT were more likely to be node-positive. Likewise, in comparison with women randomized to placebo, the death rate from breast cancer was marginally higher among women randomized to HT.

Earlier observational studies suggested that breast cancers occurring in women using combination HT had more favorable characteristics and were associated with less mortality than tumors that occur in non-users of HT. This current report from the WHI, which is in agreement with findings from the British Million Women Study,[3] clarifies that breast cancer mortality is indeed increased in women who have used combination HT.

With the publication of this important report, some healthcare providers will recommend that no menopausal women should be prescribed hormone therapy. I will now incorporate an increased risk for mortality from breast cancer into my counseling of patients considering initiating or continuing combination HT.

This new WHI publication also heightens the importance of exploring whether micronized progesterone, when combined with estrogen, may have less impact on breast cancer mortality, a possibility raised by findings of a large French study.[4]

Finally, given the possible cardioprotection noted when HT is started by women within 10 years of the onset of menopause,[5] a WHI report that incorporates the lengthy follow-up employed in this current publication and addresses all-cause mortality (including from coronary artery disease, breast cancer, and other conditions) would help women and clinicians as they make decisions regarding use of combination HT. Thank you.


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