Breast cancer and hormone replacement therapy.

Understanding the association between hormone replacement therapy (HRT), the diagnosis of breast cancer, and the clinical outcome of women who develop breast cancer in the setting of HRT continue to present important challenges for health professionals and the public. The general impression in the medical community is that breast cancer is diagnosed more frequently after prolonged HRT; however, whether a causative relationship exists between HRT and breast cancer remains uncertain. Despite the increase in breast cancer diagnosis, clinical outcome of the disease appears favorable for women who develop breast cancer after HRT; HRT users tend to present with more localized tumors that exhibit favorable histology, and overall death from breast cancer appears reduced. The history of breast cancer constitutes a contraindication for HRT as a general rule, based on the concern that HRT may activate dormant cancer cells. Direct evidence for this practice is very limited; available studies are small and mostly retrospective, but do not indicate an adverse effect of HRT on breast cancer recurrence. In reaching a clinical decision regarding HRT, the expected benefits (largely improvement of menopausal symptoms) must be weighed against the potential risks of HRT (especially breast cancer) for each individual woman.