In a recently published investigation , Calle and colleagues selected a large cohort of postmenopausal US women (n = 67,754) from the 97,786 female participants of the prospective study Cancer Prevention Study II Nutrition Cohort. This cohort was established in 1982 by the American Cancer Society. Women aged 50–74 years were mailed self-administered questionnaires from 1992, with follow-up questionnaires being sent in 1997, 1999, 2001 and 2003. The follow-up period ended in June 2005, with an 89% response rate.
Of the respondents, 47.6% were never-users of hormone replacement therapy (HRT), 21.2% current estrogen-only users, 13% were current estrogen + progestogen users, 14.6% were former estrogen-only users and 3.6% were former estrogen + progestogen users. The incidence rates of breast cancer were significantly higher among current users of estrogen + progestogen compared with never-users for both ductal (relative risk (RR) 1.75; 95% confidence interval (CI) 1.53–2.01) and lobular cancer (RR 2.07; 95% CI 1.62–2.77). Risk increased within 2–3 years of usage and attenuated after this. Estrogen-only use was not associated with an overall increased risk of ductal carcinoma except in lean women (body mass index < 25 kg/m2) and in cancers diagnosed at the distant metastasis stage. The timing of mammographic screening was controlled for in the analysis.
Queen Charlottes & Chelsea Hospital, London, UK
Calle EE, Feigelson HS, Hildebrand JS, Teras LR, Thun MJ, Rodriguez C. Postmenopausal hormone use and breast cancer associations differ by hormone regimen and histological subtypes. Cancer 2009;115:936-45. Published March 1, 2009.
Beral V; Million Women Study Collaborators. Breast cancer and hormone-replacement therapy in the Million Women Study. Lancet 2003;362:419-27.
Writing Group for the Womens Health Initiative Investigators. Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results from the Womens Health Initiative randomized controlled trial. JAMA 2002;288:321-33.
The Womens Health Initiative Steering Committee. Effects of conjugated equine estrogen in postmenopausal women with hysterectomy: the Womens Health Initiative randomized controlled trial. JAMA 2004;291:1701-12.
Fournier A, Fabre A, Mesrine S, Boutron-Ruault MC, Berrino F, Clavel-Chapelon F. Use of different postmenopausal hormone therapies and risk of histology- and hormone receptor-defined invasive breast cancer. J Clin Oncol 2008;26:1260-8.