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Hormone Replacement Therapy and Breast Cancer Risk
WHI trials review progestin plus estrogen and estrogen alone
The use of progestin and estrogen for menopausal hormonal therapy has a higher risk of breast cancer than estrogen therapy alone, according to a longer-term study of 27,347 postmenopausal women in 2 trials of the Women’s Health Initiative who were followed for an average of 13 years.
The first trial included 16,608 women with a uterus who were randomized to receive either 0.625 mg of conjugated equine estrogens (estrogen) plus 2.5 mg mederoxyprogesterone acetate (progestin) or placebo. The following hazard ratios (HR) for breast cancer were associated with different phases of care:
• 0.71 HR during the first 2 years of therapy
• 1.24 HR for the remaining intervention
• 1.23 HR during the initial postintervention phases
• 1.37 HR at 5 years post-treatment
The second trial involved 10,739 women with a prior hysterectomy who were randomized to receive either 0.625 mg estrogen or placebo. The following HRs for breast cancer were associated with different phases of care:
• 0.79 HR during the intervention phase
• 0.55 HR in the early postintervention phase
• 1.17 at late postintervention follow up
Citation: Chelbowski RT, Rohan TE, Manson JE, et al. Breast cancer after use of estrogen plus progestin and estrogen alone: analyses of data from 2 Women’s Health Initiative randomized clinical trials. JAMA Oncol. 2015. Doi:10.1001/jamaoncol.2015.0494