Hormone receptors and breast cancer--an occasional survey.

Hormone receptors are proteins, localised in the membrane, cytosol, mitochondrion or nucleus of target cells; binding of hormone to the receptor leads to alterations in intracellular activity or growth. The development of antagonists which competitively bind to receptor sites has been used clinically to block, for example, the action of androgen, histamine, adrenaline and oestrogen. In patients with breast cancer, measurements of hormone receptor activity are valuable (1) in predicting which patients with advanced disease will respond to endocrine therapy, (2) as an additional independent guide to the patients' prognosis. The anti-oestrogen, tamoxifen has few side-effects and is therefore particularly useful in the treatment of advanced disease. In addition, two trials, performed in the USA, suggest that this receptor-blocker may be valuable in the adjuvant treatment of early disease. In the UK, further trials are underway to confirm this and to assess the relationship of hormone receptor status in the primary tumour to benefit from treatment.