Breast Cancer and HRT: Collaborative Reanalysis of Data

Abstract

Large numbers of epidemiological studies of the relationship between use of oral contraceptives and hormone replacement therapy (HRT) on the one hand and the risk of breast cancer on the other have been published over the past two decades. The results have generally been regarded as conflicting and difficult to interpret. Some years ago, Professor Valerie Beral (Director of the Imperial Cancer Research Fund Cancer Epidemiology Unit, Oxford, UK) decided that the best way forward would be to undertake a collaborative re-analysis of the studies. She and her team succeeded in gaining the support of almost all the investigators worldwide and in 1996 a collaborative re-analysis of the data on breast cancer and oral contraceptive use was published [1]. This was followed by a similar reanalysis concerning the data on breast cancer and hormone replacement therapy which appeared in 1997 [2]. The latter analysis is the subject of the present report.