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Chlebowski RT, Anderson GL, Gass M, et al. Estrogen Plus Progestin and Breast Cancer Incidence and Mortality in Postmenopausal Women. JAMA. 2010;304(15):1684–1692. doi:10.1001/jama.2010.1500
Author Affiliations: Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California (Dr Chlebowski); Fred Hutchinson Cancer Research Center, Seattle, Washington (Drs Anderson and Prentice and Mr Aragaki); University of Cincinnati, Cincinnati, Ohio (Dr Gass); State University of New York at Stony Brook (Dr Lane); University of Pittsburgh, Pittsburgh, Pennsylvania (Dr Kuller); Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts (Dr Manson); Stanford Prevention Research Center, Stanford, California (Dr Stefanick); University of Massachusetts/ Fallon Clinic, Worcester (Dr Ockene); University of Wisconsin, Madison (Dr Sarto); University of Tennessee Health Science Center, Memphis (Dr Johnson); University at Buffalo, Buffalo, New York (Dr Wactawski-Wende); Cancer Therapy and Research Center (Dr Ravdin) and University of Texas Health Science Center (Dr Schenken), San Antonio; Wayne State School of Medicine and Hurtzel Hosptial, Detroit, Michigan (Dr Hendrix); Baylor College of Medicine, Houston, Texas (Dr Rajkovic); Albert Einstein College of Medicine, New York, New York (Dr Rohan); and University of California at Davis, Sacramento (Dr Yasmeen).
Context In the Women's Health Initiative randomized, placebo-controlled trial of estrogen plus progestin, after a mean intervention time of 5.6 (SD, 1.3) years (range, 3.7-8.6 years) and a mean follow-up of 7.9 (SD, 1.4) years, breast cancer incidence was increased among women who received combined hormone therapy. Breast cancer mortality among participants in the trial has not been previously reported.
Objective To determine the effects of therapy with estrogen plus progestin on cumulative breast cancer incidence and mortality after a total mean follow-up of 11.0 (SD, 2.7) years, through August 14, 2009.
Design, Setting, and Participants A total of 16 608 postmenopausal women aged 50 to 79 years with no prior hysterectomy from 40 US clinical centers were randomly assigned to receive combined conjugated equine estrogens, 0.625 mg/d, plus medroxyprogesterone acetate, 2.5 mg/d, or placebo pill. After the original trial completion date (March 31, 2005), reconsent was required for continued follow-up for breast cancer incidence and was obtained from 12 788 (83%) of the surviving participants.
Main Outcome Measures Invasive breast cancer incidence and breast cancer mortality.
Results In intention-to-treat analyses including all randomized participants and censoring those not consenting to additional follow-up on March 31, 2005, estrogen plus progestin was associated with more invasive breast cancers compared with placebo (385 cases [0.42% per year] vs 293 cases [0.34% per year]; hazard ratio [HR], 1.25; 95% confidence interval [CI], 1.07-1.46; P = .004). Breast cancers in the estrogen-plus-progestin group were similar in histology and grade to breast cancers in the placebo group but were more likely to be node-positive (81 [23.7%] vs 43 [16.2%], respectively; HR, 1.78; 95% CI, 1.23-2.58; P = .03). There were more deaths directly attributed to breast cancer (25 deaths [0.03% per year] vs 12 deaths [0.01% per year]; HR, 1.96; 95% CI, 1.00-4.04; P = .049) as well as more deaths from all causes occurring after a breast cancer diagnosis (51 deaths [0.05% per year] vs 31 deaths [0.03% per year]; HR, 1.57; 95% CI, 1.01-2.48; P = .045) among women who received estrogen plus progestin compared with women in the placebo group.
Conclusions Estrogen plus progestin was associated with greater breast cancer incidence, and the cancers are more commonly node-positive. Breast cancer mortality also appears to be increased with combined use of estrogen plus progestin.
Trial Registration clinicaltrials.gov Identifier: NCT00000611
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