Long-term Survival Improved for Women with Early Breast Cancer

New data from ATAC, one of the world’s largest and longest-running breast cancer trials in postmenopausal women with early breast cancer, was presented at the San Antonio Breast Cancer Symposium (SABCS) in the United States on 15 December. After 100 months of follow-up, these data show that anastrozole (Arimidex) can help many more women live cancer-free, for longer. Anastrozole, an aromatase inhibitor, has been shown to be better than tamoxifen in preventing tumours from returning in postmenopausal women with hormone-sensitive early breast cancer.1 Preventing breast cancer from returning (“recurrence”) is the key to saving lives because if cancer returns, women are much more likely to die.

Importantly, this data shows that even four years after a woman’s treatment ends, the protective effect of anastrozole in reducing the risk of hormone-sensitive early breast cancer from returning continues to increase. Overall, women in the ATAC trial taking anastrozole were 24% less likely to have their cancer come back, compared with those taking tamoxifen.¹ This data provides strong evidence for starting treatment with anastrozole, in preference to tamoxifen, soon after diagnosis, to give women the best chance of remaining cancer-free long term. Breast cancer currently affects 1.1 million women worldwide per year² and hormone-sensitive early breast cancer accounts for around 75% of all cases of breast cancer in postmenopausal women.³The ATAC trial is an international study which was conducted in Australia and New Zealand by the Australian New Zealand Breast Cancer Trials Group (ANZ BCTG). This Group is Australia’s premier breast cancer research body conducting research for prevention, treatment and cure of breast cancer through a collaborative national clinical trials research program. Presenting the data at the 2007 SABCS, Professor John Forbes said: “Preventing recurrence is of utmost importance in breast cancer management. If we can stop the cancer from returning, we can save more lives, more often. 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.”Professor Forbes continued: “Prior to the ATAC trial, tamoxifen was the standard of care for women with hormone-sensitive disease, with substantial evidence to support its crucial place in practice. However, these new 100-month data from ATAC show us that compared with tamoxifen, anastrozole can significantly reduce the risk of recurrence and minimise life-threatening side effects. Most encouragingly, the data also show us that the protective effect of anastrozole lasts well beyond the standard treatment period of five years.”The impact of treatment on quality of life is also an important consideration in early breast cancer, and data have shown that the clinical benefits of anastrozole are achieved without adversely affecting the quality of patients’ lives.⁴The ATAC trial has provided important information on the long term safety profile of anastrozole compared to tamoxifen. No new morbidities or mortalities were seen and fracture rates, which had been noted to be higher for women taking anastrozole, were no longer different once treatment had ceased. Endometrial cancer rates, previously noted to be higher for women taking tamoxifen, remained significantly higher for these women after their tamoxifen treatment had stopped.Results from the ATAC trial confirm the importance of supporting large, quality clinical trials to obtain rigorous, scientific data for the ongoing safety and efficacy of new treatments. Such support may ensure that positive results are translated into new best practice treatment to provide women the greatest chance of long term survival.Professor Forbes concluded, “On behalf of the ATAC investigators in the ANZ BCTG, we thank all the women in Australia and New Zealand who have made a significant contribution to these results by their involvement in ATAC. These results will improve the outcomes for patients worldwide.”References

1. Forbes J, on behalf of the ATAC Trialist’s Group. ATAC: 100 month median follow-up shows continued superior efficacy and no excess fracture risk for anastrozole compared with tamoxifen after treatment completion. Abstract no 41. San Antonio Breast Cancer Symposium 2007.

2. Parkin DM, Laara E, Muir CS. Estimates of the worldwide frequency of sixteen major cancers in 1980. Int J Cancer 1988; 41(2): 184-97.
3. Breastcancer.org. What role do hormones play in breast cancer treatment. Available from url: http://www.breastcancer.org/treatment/hormonal/what_is_it/hormone_role.jsp. (Last accessed October 2007)
4. Cella et al. Quality of life of postmenopausal women in the ATAC (‘Arimidex’, Tamoxifen, Alone or in Combination) trial after completion of 5 years’ adjuvant treatment for early breast cancer. Breast Cancer Research and Treatment 2006; 100(3): 273-84.

(Source: Australian New Zealand Breast Cancer Trials Group : January 2008)