Breast cancer and hormone-replacement therapy: the Million Women Study

Sir The Million Women Study (MWS) collaborators (Aug 9, p 419)1 report a doubling of the risk of incident invasive breast cancer in current-users of combined hormone-replacement therapy (HRT) compared with never-users, causing considerable alarm among patients, doctors, and the pharmaceutical indust...

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Published in:	The Lancet (British edition) 2003-10, Vol.362 (9392), p.1328-1328
Main Author:	Garton, Mark
Format:	Article
Language:	eng
Subjects:	Breast cancer Breast Neoplasms - chemically induced Breast Neoplasms - epidemiology Breast Neoplasms - prevention & control Estrogen Replacement Therapy - adverse effects Estrogens Female Health risk assessment Hormone replacement therapy Humans Incidence Mammography Pharmaceutical industry Placebos Research Design - standards Risk Risk Assessment Risk Factors Womens health
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Summary:	Sir The Million Women Study (MWS) collaborators (Aug 9, p 419)1 report a doubling of the risk of incident invasive breast cancer in current-users of combined hormone-replacement therapy (HRT) compared with never-users, causing considerable alarm among patients, doctors, and the pharmaceutical industry.2 Media medics urged calm by emphasising absolute rather than relative risk, but for many women the damage was done. [...]differences could be important, since the mean duration of follow-up was only 2·6 years, before most participants had attended for their next screening mammogram. Because only half the annual burden of breast cancers in this age group is detected by screening (Cook A, Ninewells Hospital, Dundee, UK, personal communication), the proportion of incident cancers detected by screening in the MWS would be relevant. Ascertainment bias might account in part for the observed increase in risk among HRT users, despite the potential adverse effect of HRT on sensitivity of mammographic screening.3 The Collaborators believe their results are consistent with those of the Women's Health Initiative (WHI) trial,3,4 in which healthy postmenopausal women were randomly assigned conjugated equine oestrogen plus medroxyprogesterone acetate, or placebo.
ISSN:	0140-6736 1474-547X