Biological background to aromatase inhibition

Highly specific and potent aromatase inhibitors are becoming available for the treatment of advanced breast cancer and trials of their use in the adjuvant setting have started. There is a good understanding of the role of aromatase in the determination of plasma oestrogen levels and (in premenopausal women) of its endocrine control. However, there is not a clear relationship between plasma oestrogens and oestrogen-dependent tumour growth and the role of intratumoural aromatase needs to be determined. To ensure optimal usage of the new aromatase inhibitors it is essential are improve our understanding of the intratumoural effects of these drugs.