SAN ANTONIO, Texas, December 16 /PRNewswire/ --
- Safety and Tolerability Advantages With 'Arimidex' Pave the Way for New Treatment Combinations and Potential in Breast Cancer Prevention
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FOR INTERNATIONAL JOURNALISTS - NOT FOR US MEDIA
Data presented for the first time at the 29th Annual San Antonio Breast Cancer Symposium (SABCS) confirm that after five years of adjuvant breast cancer treatment, 'Arimidex' (anastrozole) performs significantly better than tamoxifen across a number of crucial safety and tolerability parameters, including endometrial abnormalities and venous thromboembolic events(1,2).
'Arimidex' has already been shown to be significantly more effective than tamoxifen in postmenopausal hormone-sensitive early breast cancer, preventing the disease returning in an additional one in four women compared with the older drug(3). The latest data also confirm that women prescribed 'Arimidex' will experience fewer life-threatening side effects than those on tamoxifen(1,2), further reducing the burden of the disease in these patients.
'Arimidex' - fewer endometrial abnormalities
The six-year results from a prospective sub-protocol of the 'Arimidex', Tamoxifen, Alone or in Combination (ATAC) trial, presented this week, confirm that 'Arimidex' is associated with a third fewer endometrial abnormalities than tamoxifen (27% versus 44% respectively, p=0.17) (2). These data suggest that, unlike tamoxifen, 'Arimidex' does not have a stimulatory effect on the endometrium2. These data also support earlier findings from the main ATAC trial which showed that treatment with tamoxifen led to a significantly higher incidence of vaginal bleeding and a four-fold increase in hysterectomy compared with 'Arimidex' (3,4).
Dr. Sean Duffy from St James' University Hospital, Leeds, UK, commented, "It can be highly distressing for a woman to undergo invasive gynaecological investigations, in order to rule out the possibility of endometrial cancer, when she's already experienced the trauma of surgery for breast cancer. These long-term data from ATAC, together with these updated safety data, suggest that treating patients with 'Arimidex' instead of tamoxifen for early breast cancer can help spare more women the fear of these types of side effects, which are also a costly burden on the healthcare system."
'Arimidex' - fewer venous thromboembolic events
Results from an additional analysis of ATAC trial (at 68 months follow-up), presented for the first time at SABCS, demonstrate that women treated for five years with 'Arimidex' experienced 39% fewer venous thromboembolic events (VTEs), such as deep vein thrombosis or pulmonary embolism, compared to those treated with tamoxifen (p<0.0001)(2).
Importantly, the risk of developing excess VTEs with tamoxifen occurs early after treatment initiation and remains elevated throughout the five-year treatment period. These findings further support initiating and continuing adjuvant treatment with 'Arimidex' instead of tamoxifen.
'Arimidex' safety profile - the long-term implications
These mature data from the ATAC trial confirm that the risk:benefit ratio in early breast cancer continues to favour 'Arimidex' over tamoxifen. As confidence in the 'Arimidex' efficacy and safety profile builds within the oncology community, so does the potential for this drug to be explored in combination with other treatments and as a preventative therapy.
The TAnDEM (TrAstuzumab in Dual HER2 ER-positive Metastatic breast cancer) study, presented for the first time in the USA today, shows that treatment with 'Arimidex' plus Herceptin (trastuzumab) keeps hormone-sensitive, HER2-positive tumours under control for significantly longer than hormonal therapy alone (median progression-free survival = 4.8 months vs. 2.4 months respectively) (5). Although only 25% of breast cancers are both HER2-positive and hormone sensitive, these types of cancer are particularly aggressive and do not generally respond well to hormonal therapy alone. Previous trends in advanced breast cancer treatment suggest that the 'Arimidex' plus Herceptin combination may impact the way that so called "co-positive" breast cancer is treated in the early stages.
As the overall treatment paradigm shifts, the safety profile of 'Arimidex' may also influence the prevention options available for healthy women at high risk of developing hormonal breast cancer. The potential for this was boosted today by the presentation of the first safety data from the International Breast Cancer Intervention Study, IBIS II, suggesting that 'Arimidex' does not pose any significant safety concerns with respect to cholesterol levels or cognitive functioning in the test population(6,7).
"The long-term safety profile of anastrozole provides a strong argument for using anastrozole instead of tamoxifen in the early breast cancer setting. But, even more importantly, these safety data, coupled with the fact that anastrozole is highly effective at preventing the development of new cancers in the opposite breast (contralateral breast cancer), continue to support anastrozole as a very strong candidate for breast cancer prevention in postmenopausal women," commented Jack Cuzick, John Snow Professor of Epidemiology at Queen Mary, University of London, leading researcher from Cancer Research UK and IBIS-II Steering Committee co-chairman. "Although we do not yet have efficacy data from the IBIS II trial, the safety profile of anastrozole in early breast cancer indicates that, compared with tamoxifen, it could be a viable option for preventive therapy in high-risk women who are otherwise healthy."
References
1. S Duffy et al. Anastrozole is associated with a lower risk of endometrial abnormalities than tamoxifen: first report of the ATAC trial endometrial sub-protocol at six years' follow-up. Abstract No: 4055. San Antonio Breast Cancer Symposium 2006.
2. J Cuzick et al. A detailed analysis of the benefits of anastrozole over tamoxifen for venous thromboembolic events (VTEs) after five years' treatment. Abstract No: 104. San Antonio Breast Cancer Symposium 2006.
3. ATAC Trialists' Group. Results of the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial after completion of five years' adjuvant treatment for breast cancer. Lancet. 2005; 365 (9453):60-62.
4. S Duffy on behalf of the ATAC Trialists' Group. Gynaecological adverse events including hysterectomy occur less frequently with anastrozole than with tamoxifen: data from the ATAC ('Arimidex', Tamoxifen, Alone or in Combination) trial. Proc ASCO 2005.
5. JR Mackey et al. Trastuzumab prolongs progression-free survival in hormone-dependent and HER2-positive metastatic breast cancer (MBC). Abstract No: 3. San Antonio Breast Cancer Symposium 2006.
6. V Jenkins et al. Preliminary results from the IBIS II (prevention) cognitive sub-protocol. Abstract No: 5076. San Antonio Breast Cancer Symposium 2006.
7. S Singh et al. Effect of anastrozole on cholesterol fractions in postmenopausal women with high risk of breast cancer: Results from IBIS-II Breast Cancer Prevention Study. Abstract No:1055. San Antonio Breast Cancer Symposium 2006.
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Notes to Editors
About IBIS II
The International Breast Cancer Intervention Study II (IBIS-II), a randomised, blinded placebo controlled clinical trial, has been designed to investigate 'Arimidex' in women in 25 countries, who are at an increased risk of breast cancer.
The study is divided into two parts:
- The IBIS-II Prevention part of the study aims to recruit 6,000 postmenopausal women who are at increased risk of developing breast cancer. A number of factors for increased risk can make a woman eligible to enter the study and these are set according to the different age groups. Women can take part in the trial if they are aged between 40-70 years and are not on HRT.
- The second part of the study, IBIS-II (DCIS), will recruit 4,000 women who have been diagnosed with and had surgery to remove a particular early form of breast cancer, which is not growing or spreading, known as DCIS (Ductal carcinoma in situ). As well as being at high risk of developing more advanced forms of breast cancer, these women are also more likely to develop a new tumour in the opposite breast. This part of the trial is designed to determine which of the two drugs, anastrozole or tamoxifen, can best prevent new cancers, both in the breast affected by DCIS and in the opposite breast.
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