Use of aromatase inhibitors in the adjuvant treatment of breast cancer.

The value of endocrine treatment of early breast cancer has been illustrated by the antioestrogen, tamoxifen, which has now been available for nearly 30 years. However, if the recognised side effects and pharmacological properties of tamoxifen are taken into consideration, it is possible that other endocrine treatments that are now available can provide equal or superior efficacy, along with improved tolerability. One such group of agents is the aromatase inhibitors specifically the new-generation triazole aromatase inhibitors, such as anastrozole and letrozole, which have both shown tolerability and efficacy advantages over standard treatments in postmenopausal women with advanced breast cancer. There are convincing reasons why the new generation of aromatase inhibitors have advantages over tamoxifen. For instance, from their agonist properties, the effects on the endometrium and tumour stimulation seen with tamoxifen would not be expected, nor would the visual disturbances that have been associated with the triphenylethylene compounds, including tamoxifen. A number of aromatase inhibitors, for instance, anastrozole, letrozole and exemestane, are currently being investigated for treatment of early breast cancer. The results of the trials of aromatase inhibitors and tamoxifen will, in the next few years, define whether or not the new-generation aromatase inhibitors have a role to play in the treatment of postmenopausal women with early breast cancer.