Long-Term Safety Data for Arimidex(TM) (Anastrozole) Reinforce Patient Benefits Over Tamoxifen in Early Breast Cancer

San Antonio, Texas (ots/PRNewswire) -

- Safety and Tolerability Advantages With 'Arimidex' Pave the Way
for New Treatment Combinations and Potential in Breast Cancer
Prevention

For Health Professional Press Only

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.

AstraZeneca (NYSE:AZN) is a major international healthcare
business engaged in the research, development, manufacture and
marketing of prescription pharmaceuticals and the supply of
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companies with healthcare sales of US$23.95 billion and leading
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ARIMIDEX is a trademark, the property of the AstraZeneca group of
companies.

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