Arimidex shows survival benefit in early breast cancer

Data at the San Antonio Breast Cancer Symposium (SABCS), Texas, US showed AstraZeneca's Arimidex (anastrozole) to be the first aromatase inhibitor (AI) to provide an overall survival benefit, compared with tamoxifen, in the treatment of hormone-sensitive early breast cancer.

Three international trials were designed to assess whether replacing tamoxifen with Arimidex after two to three years of therapy was more effective than remaining on tamoxifen for the full five year treatment period. Post-menopausal women who replaced tamoxifen with Arimidex in their treatment for early breast cancer showed a reduction in the likelihood recurrence by almost 50%, while their risk of death fell by nearly a third.

At a median follow-up of 30 months, Arimidex patients experienced a 29% improvement in overall survival; 45% improvement in 'event-free survival', ie, no disease recurrence of a local, contralateral or distant nature; and a 39% improvement in distant recurrence-free survival.

In the landmark Arimidex, Tamoxifen, Alone or in Combination (ATAC) Trial, women taking Arimidex for the full five year treatment period showed a significantly reduced risk of disease recurrence compared with tamoxifen, especially during the first three years following surgery. They also experience fewer serious side effects, and although Arimidex, like all Ais, increases the risk of bone fracture compared with tamoxifen, it is possible to predict which women may be most at risk of fracture, which is not the case with the more serious side effects associated with tamoxifen.

'The ATAC trial has confirmed that starting treatment with anastrozole at the earliest opportunity after surgery, and giving it for the full five years of treatment, is more effective than tamoxifen for the prevention of disease recurrence,' said Prof Jeffrey Tobias of the University College London Hospitals, UK. 'This would suggest that the best place to use anastrozole is right from the start. These new data are important news for women currently taking tamoxifen who can still gain from the significant benefits of anastrozole by switching at two years.'

Arimidex is currently indicated for adjuvant treatment of early breast cancer in 81 markets based on superiority over tamoxifen in the ATAC trial. It has a broad licence for the US, Japan and a number of European markets, and in June 2005 was granted indication for adjuvant treatment of post-menopausal women with hormone receptor positive early invasive breast cancer from the Medicines and Healthcare Products Regulatory Agency (MHRA) in the UK, which in turn lead to approvals in five other European countries under the Mutual Recognition Variation Procedure. For the nine months of 2005, worldwide sales reached $856m.