Research

Hormonal

Current use of postmenopausal hormone therapy (estrogen alone or estrogen plus progestin) significantly increases the risk of invasive breast cancer, with the risk rising significantly after five or more years of use and being highest in women over age 55.

If you are a postmenopausal woman considering hormone therapy, be aware that current use of estrogen (alone or with progestin) increases breast cancer risk, especially if you are over 55 and use it for more than five years. Discuss these specific risks with your doctor to weigh them against potential benefits.

StrongSupportsHIGH confidence
The risk of breast cancer was significantly increased among women who were currently using estrogen alone (relative risk, 1.32; 95 percent confidence interval, 1.14 to 1.54) or estrogen plus progestin (relative risk, 1.41; 95 percent confidence interval, 1.15 to 1.74)... The increased risk of breast cancer associated with five or more years of postmenopausal hormone therapy was greater among older women (relative risk for women 60 to 64 years old, 1.71; 95 percent confidence interval, 1.34 to 2.18).
Graham A. Colditz et al. · New England Journal of Medicine · 1995

Why this rating

Large prospective cohort study (Nurses' Health Study) with long follow-up (725,550 person-years) and high case confirmation rates.

Source

The Use of Estrogens and Progestins and the Risk of Breast Cancer in Postmenopausal Women

Graham A. Colditz et al. · New England Journal of Medicine · 1995

DOI 10.1056/nejm199506153322401

cohort · n=69586Cited 1,509×
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DOI resolved against Crossref · corpus check 2026-06-10

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