The Pharmaceutical Journal
Vol 273 No 7329 p841
11 December 2004

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Anastrazole should be preferred initial treatment

Anastrazole should be the preferred initial treatment for postmenopausal women with localised hormone-receptor positive breast cancer, according to final results from the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial.

The ATAC trial compared five years of using the aromatase inhibitor anastrazole (Arimidex) alone or tamoxifen alone with both drugs in combination, as adjuvant therapy in 9,366 postmenopausal women with localised breast cancer. Initial analyses of trial results showed that anastrazole prolonged disease free survival compared with tamoxifen (PJ, 15 November 2003) and reduced the incidence of contralateral breast cancer.

Five-year follow up data published this week show that, compared with tamoxifen, anastrazole increases disease free survival (575 vs. 651 events, hazard ratio 0.87, 95 per cent confidence interval 0.78–0.97) and time to recurrence (402 vs. 498, hazard ratio 0.79, CI 0.70–0.90). These advantages were greater for hormone receptor positive patients. The incidence of contralateral breast cancer was reduced by 53 per cent with anastrazole in hormone-receptor positive patients (95 per cent CI 25–71). Overall survival was similar for both drugs although withdrawal due to adverse events was less common with anastrazole (11.1 per cent) than tamoxifen (14.3 per cent, P=0.0002).

Compared with tamoxifen, anastrazole treatment was associated with significant reductions in the incidence of endometrial cancer, thromboembolic events, ischaemic cerebrovascular events, vaginal bleeding, hot flushes and vaginal discharge, although fracture rates and arthralgia were more common in the anastrazole group.

The researchers say that although their results are only applicable to anastrazole, current data suggest that it is not appropriate to wait five years before starting an aromatase inhibitor, and say that the most effective and well tolerated therapy should be offered at the earliest opportunity.

The trial, published early online (www.thelancet.com), was sponsored by AstraZeneca.