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Anastrozole Superior to Tamoxifen in Early Post-menopausal Breast Cancer: Presented at ESMO

By David J.E. Candlish

NICE, FRANCE -- October 21, 2002 -- Anastrozole is superior to tamoxifen in the treatment of postmenopausal women with early-stage breast cancer, according to a study presented at the 27^th Congress of the European Society for Medical Oncology.

Dr. Michael Baum, from University College, London, United Kingdom, presented the first results from the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial, which indicate that anastrozole shows significantly better efficacy than tamoxifen with regard to time to recurrence in the adjuvant therapy of postmenopausal women with early breast cancer.

Tamoxifen has been the gold standard in the treatment of hormone-sensitive breast cancer for the past 30 years. Although generally well tolerated, long-term use of tamoxifen has been associated with an increased risk of endometrial cancer and thromboembolic disorders, creating a demand for an alternative.

Anastrozole is an orally active, nonsteroidal agent that suppresses oestrogen levels via inhibition of the aromatase enzyme. Some studies have shown that anastrozole is superior to tamoxifen as a first-line therapy in postmenopausal patients with hormone-sensitive tumours, leading to its use in this setting.

The ATAC trial reported here was set up to compare the efficacy and safety of anastrozole alone with that of tamoxifen and the combination of anastrozole and tamoxifen with that of tamoxifen alone as adjuvant treatment for postmenopausal women with early breast cancer, following primary therapy.

The trial involved more than 9000 patients who were randomised to one of three treatment arms; all arms received treatment for 5 years. All patients had histologically proven operable invasive breast cancer, were aged 45 years or older, and were naturally or artificially postmenopausal.

First results indicate that anastrozole shows significantly better efficacy than tamoxifen with regard to time to recurrence, while the combination of anastrozole with tamoxifen shows similar efficacy to tamoxifen alone. Anastrozole alone appears to be more effective than the combination. Results also indicate a significantly lower risk of contralateral breast cancer with anastrozole alone than with tamoxifen alone.

With regard to adverse events, tamoxifen was associated with a lower incidence of musculoskeletal disorders and fractures, whereas anastrozole was associated with a lower incidence of thromboembolic events, endometrial cancer, and hot flushes.

These results indicate that anastrozole may now be an effective alternative adjuvant therapy to tamoxifen in postmenopausal women with early-stage breast cancer.

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