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HEALTH PROFESSIONALS > DISCUSSION TOPICS > AROMATASE INHIBITORS IN EARLY BREAST CANCER > AROMATASE INHIBITORSAromatase inhibitors
Aromatase inhibitors are only suitable for use in women who have been through the menopause. After the menopause, oestrogen is mainly produced by a process called aromatisation; the conversion of androgens (produced by the adrenal glands) into oestrogens. This process occurs mainly in the fatty tissues of the body. Aromatase inhibitors block this process, thus stopping the production of oestrogen in post menopausal women.
Third generation aromatase inhibitors have been used for the treatment of advanced oestrogen receptor positive breast cancer since the mid 1990’s. Those in use are anastrozole (Arimidex), letrozole (Femara) and exemestane (Aromasin).
Anastrozole is a highly selective non-steroidal aromatase inhibitor, licensed for use both in advanced breast cancer and early stage breast cancer.
Letrozole is also a highly selective non-steroidal aromatase inhibitor. It is licensed for use in advanced breast cancer and for use in early stage breast cancer either following surgery or following adjuvant tamoxifen therapy. It may also be used as neo-adjuvant therapy.
Exemestane is an irreversible steroidal aromatase inhibitor, licensed for use in advanced breast cancer and also for early breast cancer after initial treatment of 2–3 years of tamoxifen therapy.
Studies comparing the use of anastrozole with tamoxifen for advanced breast cancer have indicated that anastrozole is at least as good as tamoxifen in the overall population. It results in a significant improvement in time to progression in patients with known hormone-receptor-positive disease, when compared with tamoxifen. Similar results have been obtained with exemestane.
Studies comparing letrozole and tamoxifen in advanced breast cancer showed letrozole to be superior to tamoxifen in all end points. This was regardless of subgroups. There was a longer period of time before patients needed chemotherapy with letrozole than with tamoxifen (1).
The ATAC Study
The ATAC study was originally designed to answer three questions: (a) is anastrozole at least as effective as tamoxifen in post menopausal women with early operable breast cancer (b) does anastrozole offer any safety or side-effect benefits over tamoxifen in this group of patients (c) could a combination of anastrozole and tamoxifen offer additional efficacy or safety benefits over tamoxifen alone (2).
Since the ATAC trial commenced, other studies have also looked at the use of third generation aromatase inhibitors for early stage breast cancer.
Content last reviewed: 01 July 2006
Page last modified: 19 April 2007
Page last modified: 19 April 2007