The Vital First Years in Breast Cancer Care: New Data Confirm That Using 'Arimidex' (anastrozole) From the Start Can Help More Women Live Cancer-Free for Longer

MACCLESFIELD, England, May 16 /PRNewswire/ -- Today, the crucial benefits of using 'Arimidex' (anastrozole) to help postmenopausal women continue to live free from breast cancer, were confirmed by the latest data from the groundbreaking ATAC* trial(1), presented at the American Society of Clinical Oncology (ASCO) Annual Meeting, in Orlando, Florida.

By comparing the real-life outcomes of women in this trial, who took either anastrozole or tamoxifen for five years following surgery for early breast cancer, it was shown that starting treatment with anastrozole can prevent many of the breast cancer recurrences that would otherwise occur if treated with tamoxifen. The data also show that using anastrozole first helps to avoid some of the life-threatening side effects that are associated with tamoxifen, such as blood clots, strokes and cancer of the womb.(2)

"Until now, women had been at highest risk of their cancer returning during the first two-to-three years following diagnosis, regardless of the treatment they receive. Looking at the number of recurrences that were prevented by anastrozole compared with tamoxifen in the ATAC trial, more than half of them occurred within the first two-and-a-half years of the five-year treatment period." explained Dr Buzdar of the MD Anderson Cancer Centre in Texas, "This clearly shows us that if women are not given the chance to start with the most effective therapy, they risk suffering a potentially fatal recurrence of their breast cancer that could otherwise have been prevented."

Protecting women from life-threatening side effects

A recognised side effect associated with tamoxifen therapy, is the increased risk of endometrial cancer. A review of the mature data from the ATAC trial has now revealed how important this can be in selecting the most appropriate treatment after surgery. Diagnoses of benign or malignant uterine tumours were three-to-four times higher in women who took tamoxifen, compared with anastrozole, and this led to almost four times more women having to undergo a hysterectomy in the tamoxifen group.(3) Blood clots, including embolus to the lung and stroke, increased by 50% in patients on tamoxifen when compared with anastrozole.

"Although anastrozole increases the risk of fracture compared with tamoxifen, we are able to identify those patients who may be more likely to have a fracture and manage them proactively," continued Dr Buzdar. "However, it is much more difficult to predict or prevent some of the life-threatening side effects we see with tamoxifen."

Looking to the long-term

The ATAC data have now confirmed that the substantial benefits that anastrozole provides women, both in terms of living free from cancer for longer and avoiding serious side effects, become apparent right from the start of treatment. However, questions remain about the benefit of initiating treatment with tamoxifen and changing therapy to an aromatase inhibitor after a few years. Professor Jack Cuzick, Cancer Research UK, Wolfson Institute of Preventive Medicine, London, used models to predict the long-term effects of these strategies, up to ten years following initial surgery.(4)

"What our model indicated was that it is always better to start and continue treatment with anastrozole, than it is to start treatment with tamoxifen and change to anastrozole at a later date," Professor Cuzick explained. "The reduction in risk may appear greater if you wait to start anastrozole after 2-3 years of tamoxifen but this is not enough to make up for the early relapses occurring in those vital first years that could have been prevented if anastrozole was used first."

But is it too late for women who have already started on tamoxifen?

Although it is now clear that women gain the most benefit from starting with anastrozole from the outset, the comprehensive portfolio of evidence for this drug shows that women who are part way through (5,6), or even reaching the end of a course of tamoxifen do not have to miss out. "Although the long-term benefits are not as great as those gained by using anastrozole from the start, switching therapy from tamoxifen to anastrozole is a better option than staying on tamoxifen for the full five years", continued Prof. Cuzick. Furthermore, new data from the ABCSG 6a study, also presented at ASCO, now show that patients who have just completed a 5-year course of endocrine therapy can extend their protection against breast cancer by taking a further three years' treatment with anastrozole.(7)

The overwhelming clinical evidence now available for anastrozole, coupled with new endorsements in clinical guidelines (8) means that more and more patients are having the opportunity to use anastrozole right from the start. According to Dr Buzdar: "One thing is now clear. Women should be given what they deserve - the best possible chance to keep breast cancer at bay at the earliest possible opportunity."

* ATAC: 'Arimidex', Tamoxifen, Alone or in Combination

References

1. ATAC Trialists' Group. Results of the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial after completion of 5 years' adjuvant treatment for breast cancer. Lancet, 365 (9453): 60-62.

2. Houghton J on behalf of the ATAC Trialists' Group. Using anastrozole as initial adjuvant treatment prevents early recurrences and reduces adverse events: Updated data from the ATAC ('Arimidex', Tamoxifen, Alone or in Combination) trial. Proc ASCO 2005; Poster Number: A8 Abstract No: 582

3. Duffy S 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

4. Cuzick JM, Howell A. Optimal timing of the use of an aromatase inhibitor in the adjuvant treatment of postmenopausal hormone receptor-positive breast cancer. Proc ASCO 2005; Poster Number: J17 Abstract No: 658

5. Kaufmann M. Benefits of switching postmenopausal women with hormone-sensitive early breast cancer to anastrozole after 2 years adjuvant tamoxifen: combined results from 3123 women enrolled in the ABCSG Trial 8 and the ARNO 95 Trial. Breast 2005;14 (Suppl 1):Abs P81 P S38.

6. Boccardo F. Switching to anastrozole (ANA) vs continued tamoxifen (TAM) treatment of early breast cancer (EBC). Updated results of the Italian tamoxifen anastrozole (ITA) trial. Proc ASCO 2005; Poster Number: 1 Abstract No: 526

7. Jakesz R. Extended adjuvant treatment with anastrozole: Results from the Austrian Breast and Colorectal Cancer Study Group Trial 6a (ABCSG-6a). Proc ASCO 2005; Poster Number: 2 Abstract No: 527

8. Winer EP, Hudis C, Burstein HJ et al. American Society of Clinical Oncology Technology Assessment on the Use of Aromatase Inhibitors As Adjuvant Therapy for Postmenopausal Women With Hormone Receptor-Positive Breast Cancer: Status Report 2004. J Clin Oncol 2005; 23 93: 1-11

Notes to editors

AstraZeneca is a major international healthcare business engaged in the research, development, manufacture and marketing of prescription pharmaceuticals and the supply of healthcare services. It is one of the world's leading pharmaceutical companies with healthcare sales of over $21.4 billion and leading positions in sales of gastrointestinal, cardiovascular, respiratory, oncology and neuroscience products. AstraZeneca is listed in the Dow Jones Sustainability Index (Global) as well as the FTSE4Good Index.

'Arimidex' is a trademark, the properties of the AstraZeneca group of companies.

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