October 22, 2001
Experts Confirm 'Arimidex' (anastrozole) as a Gold Standard
for Advanced Breast Cancer
New publication confirms the superiority of 'Arimidex' over tamoxifen in the
first-line treatment of hormone-sensitive breast cancer
- 'Arimidex' (anastrozole) should now replace tamoxifen as a first
choice, first-line therapy for post-menopausal women with hormone-
sensitive* advanced breast cancer, according to the full results of a study
involving the largest patient population ever investigated comparing these
two treatments in the advanced setting, published in the peer-review journal
The study programme involved two randomised, double blind multicentre
trials,*** one conducted in North America and Canada and the second
conducted in the rest of the world, which compared daily treatment with 'Arimidex'
1mg or tamoxifen 20mg in post-menopausal women with hormone-sensitive or
receptor unknown tumours. The data published today are the full analysis of
the combined results of these two studies, which between them, involved over
1,000 breast cancer patients.
The results in patients who had confirmed hormone-sensitive tumours (60% of
the study population and the target patients for this intervention), were
very encouraging. A retrospective analysis of this patient subgroup revealed
that 'Arimidex' was significantly superior to tamoxifen in terms of median
time to disease progression (TTP) (median 10.7 months vs 6.4 months
The investigators explored a number of possible prognostic factors which
could have contributed to the superior efficacy seen with 'Arimidex' in
these patients (age, prior treatment, presence/absence of visceral, liver or
bone metastases) and concluded that only the hormone receptor status of the
tumour had any significant impact on treatment difference. In light of this
finding, the investigators believe that the benefits of 'Arimidex' over
tamoxifen may have been diluted in the results from the overall population
by the high proportion of patients with tumours of 'unknown' hormone
receptor status included in the combined analysis (40%). The differing
mechanisms of action of the two compounds could hold the key to the
superiority of the 'Arimidex' treatment.
The potential impact of these differences in terms of treatment side effects
were also explored in the combined analysis. Both compounds were generally
well tolerated and appeared similar in terms of number of side effects
reported. However, a significantly lower incidence of thromboembolic events
were observed in patients receiving 'Arimidex' compared with those who
received tamoxifen (3.6% vs 6.5% respectively; p=0.0434, not adjusted for
multiple analysis). In addition, only 1.0% of patients taking 'Arimidex'
reported vaginal bleeding - a psychologically distressing side effect which
adversely affects quality of life - when compared with 2.2% in the tamoxifen
group. Reassuringly, given the potency of 'Arimidex' in suppressing
oestrogen synthesis, an effect which in theory might have an unfavourable
impact on bone metabolism, there was no difference between the treatment
groups in terms of bone fractures.
Reviewing these exciting new findings, the authors concluded, "In post-
menopausal women with hormonally-sensitive breast cancer, anastrozole should
be considered as the new standard first-line treatment."
Lead investigator Professor Jacques Bonneterre, Professor of Medical
Oncology, Centre Oscar Lambret, France, says, "The optimum balance of the
efficacy and tolerability data confirm that 'Arimidex' should be considered
as a new standard first-line treatment for post-menopausal women with
hormonally- sensitive breast cancer. 'Arimidex' was shown to be more
efficacious than tamoxifen in patients with hormone-sensitive disease, who
are the most appropriate group of patients for hormonal therapy in advanced
breast cancer. The data also showed 'Arimidex' to be at least as well
tolerated as tamoxifen , with a lower incidence of thromboembolic events.
Furthermore, the low incidence of vaginal bleeding observed with 'Arimidex'
provides indirect evidence of its lack of stimulatory effect on the
Because 'Arimidex' is potent and is the most selective 1, 2,3, 4 aromatase
inhibitor in the clinical setting, it provides near maximal oestrogen
suppression and is also well tolerated, while tamoxifen acts as a partial
agonist at oestrogen receptors in the breast tumour cell. The profound
reduction in circulating oestrogen levels which are achieved with 'Arimidex'
could be a more effective method of halting tumour cell proliferation than
partial oestrogen receptor inhibition. The next step will be to establish if
the proven clinical benefits of 'Arimidex' in advanced disease translate
into the early breast cancer setting, which will be revealed later this year
when results from the ATAC ('Arimidex', Tamoxifen, Alone or in Combination)
Study, involving over 9,000 patients, become available.
'Arimidex' is a trademark, the property of the AstraZeneca group of
* In these studies, hormone-sensitive refers to ER+ve and/or PR+ve tumours
** Bonneterre J, Buzdar A, Nabholtz JM, et al. Anastrozole (Arimidex) is
Superior to Tamoxifen as First-line Therapy in Hormone Receptor-positive
Advanced Breast Cancer: Results of Two Randomized Trials Designed for
Combined Analysis. Cancer, 2001
*** The North American study was conducted in 97 centres across the US and
Canada. The Rest of World study was conducted in 83 sites in Europe,
Australia, New Zealand, South America and South Africa. These studies have
been individually reported in the Journal of Clinical Oncology (Nov 2000, 18
Notes to Editors
'Arimidex' is a potent, highly selective, non-steroidal aromatase inhibitor
that exerts a therapeutic effect by inhibiting a key step in the production
of oestrogen: 'Arimidex' inhibits the conversion of androgens to oestrogens
by the enzyme aromatase. In this way, 'Arimidex' suppresses the levels of
oestrogen circulating in the blood to non-detectable levels in
'Arimidex' is currently approved for the first-line treatment of advanced
breast cancer in postmenopausal women in 24 markets, the US, UK, Italy,
France, Germany, Canada, Spain, Austria, Belgium, Brazil, Denmark, Finland,
Ireland, Luxembourg, Mexico, Netherlands, New Zealand, S. Africa, Slovakia,
Czech Republic, Malta, Norway, Australia and Switzerland.
'Arimidex' is also available in most countries for the treatment of advanced
breast cancer in postmenopausal women whose disease has progressed following
treatment with tamoxifen or other anti-oestrogens.
'Arimidex' is the most widely used aromatase inhibitor currently with over
430,000 patient years experience.