AstraZeneca is still basking in the glow of data from one of the world’s largest breast cancer trials which highlights the benefits of the firm’s Arimidex over tamoxifen in preventing all forms of disease recurrence increase over time - even four years after treatment ends.

Results from 100 months of followup in the ATAC trial, which were presented at the San Antonio Breast Cancer Symposium and published in The Lancet Oncology showed for the first time that the aromatase inhibitor Arimidex (anastrozole) has been shown to be the only treatment of its type to be increasingly better than tamoxifen in preventing tumours from returning. The study, which began in July 1996 and involved nearly 9,400 patients in 21 countries, was designed to establish whether the treatment advantages of anastrozole over tamoxifen, which had already been established in hormone sensitive advanced breast cancer, would also be seen in postmenopausal women diagnosed with early-stage disease.

The data showed that overall, women in the ATAC trial taking anastrozole were 24% less likely to have their cancer come back, compared with those taking tamoxifen, and improved disease-free survival by 15%. Also Arimidex reduced the risk of distant metastases by 16% and the incidence of contralateral breast cancer by 40%.

Presenting the data at SABCS, John Forbes, Newcastle Mater Misericordiae Hospital in Australia said that preventing recurrence is the primary goal in breast cancer management and “if we can stop the cancer from returning, we can save more lives, more often”. He noted that “these exciting long-term follow-up data show that anastrozole is a more effective treatment option than tamoxifen for postmenopausal women with hormone-sensitive early stage disease - thus it is imperative these women get the most effective treatment at the earliest opportunity after diagnosis."

Prof Forbes added that Arimidex can significantly reduce the risk of recurrence and minimise life-threatening side effects and “most encouragingly, the data also show us that the protective effect of anastrozole lasts well beyond the standard treatment period of five years”. He concluded by saying that the ATAC study “in my opinion confirms there is no longer any rationale for prescribing tamoxifen."

This data is likely to boost the sales of Arimidex which is already a big-earner for AstraZeneca with nine-month 2007 revenues of $1.26 billion.