Graham A. Colditz, Meir J . Stampfer, Walter C. Willett, David J . Hunter, J oAnn E. Manson, Charles H. Hennekens, Bernard A. Rosner and Frank E. Speizer
Received: 9 April 1992. Accepted: 16 June 1992.
Key words: breast cancer; cohort study; estrogens; progestins; Nurses' Health Study; USA.
We prospectively examined the use of hormone replacement therapy in relation to breast cancer incidence in a cohort of women 30 to 55 years of age in 1976. During 12 years of follow-up (480,665 person-years) among postmenopausal women, 1,050 incident cases of breast cancer were documented. Overall, past users of replacement estrogen were not at increased risk. After adjustment for established risk factors, type of menopause, age at menopause, and current age, the rate ratio (RR) was 0.91, 95 percent confidence interval (CI) = 0.78-1.07. the risk of breast cancer was elevated significantly among current users (RR = 1.33, Cl = 1.12-1.57); after adjusting for age, we observed no evidence of increasing risk with increasing duration of use among current users (P trend = 0.41), or among past users (P trend = 0.46). Women currently using unopposed estrogen (RR = 1.42, Cl = 1.19-1.70), estrogen and progesterone (RR = 1.54, Cl = 0.99-2.39), or progesterone alone (RR = 2.52, Cl = 0.66-9.63), were all at increased risk of breast cancer compared with never users. These data suggest that long-term past use of estrogen replacement therapy is not related to risk, that current estrogen use increases risk of breast cancer to a modest degree, and that the addition of progesterone does not remove the increased risk observed with current use of unopposed estrogen.
The authors are with the Nurses' Health Study, Channing Laboratory, Department of Medicine, Brigham and Women's H ospital, Boston, MA; and H arvard Medical School, Boston, MA, USA. Address correspondence to Dr Colditz, Channing Laboratory, 180 Longwood Ave., Boston, MA 02115-5899, USA. Supported by research grant CA40356 from the National Cancer Institute, N1 H , Department of Health and H uman Services. Dr Colditz is supported by an American Cancer Society Faculty Research Award FRA-398.
References
Kazer, Ralph R. (1995) Insulin resistance, insulinlike growth factor I and breast cancer: A hypothesis. International Journal of Cancer 62(4)
Lipworth, Loren (1995) Oral contraceptives, menopausal estrogens, and the risk of breast cancer: A casecontrol study in greece. International Journal of Cancer 62(5)
Kang, Se Chan (2006) Evaluation of oriental medicinal herbs for estrogenic and antiproliferative activities. Phytotherapy Research
Li, Christopher I. (2006) Interactions between Body Mass Index and H ormone Therapy and Postmenopausal Breast Cancer Risk (United States). Cancer Causes & Control 17 (5)
Schairer, Catherine (1994) Menopausal estrogen and estrogen-progestin replacement therapy and risk of breast cancer (United States). Cancer Causes & Control 5(6)
Magnusson, Cecilia (1996) Prognostic characteristics in breast cancers after hormone replacement therapy. Breast Cancer Research and Treatment 38 (3)
Yardley, Denise A. (2000) In Pursuit of the Prevention of Breast Cancer. The American Journal of the Medical Sciences
Modugno, Francesmary (2006) Obesity, hormone therapy, estrogen metabolism and risk of postmenopausal breast cancer. International Journal of Cancer 118(5)
Pearlstone, David B. (1999) Educational Review H ormone Replacement Therapy and Breast Cancer. Annals of Surgical Oncology 6(2)
Ioannidou-Mouzaka, Lydia (1998) Dilemmas in Breast Disease. The Breast Journal 4(6)