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| |  Arimidex (Anastrozole) Shown to be Gold Standard for Advanced Breast Cancer CHESHIRE, ENGLAND -- October 19, 2001 -- Arimidex™ (anastrozole) should now replace tamoxifen as a first choice, first-line therapy for post-menopausal women with hormone-sensitive (ER+ and/or PR+ tumours) 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 Cancer today. 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. The North American study was conducted in 97 centres across the U.S. 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 (22) 3748-3767). The studies 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 percent 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 versus 6.4 months respectively, 2P=0.022). 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 percent). 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 percent versus 6.5 percent respectively; p=0.0434, not adjusted for multiple analysis). In addition, only 1 percent of patients taking Arimidex reported vaginal bleeding -- a psychologically distressing side effect which adversely affects quality of life -- when compared with 2.2 percent 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 Jacques Bonneterre, Professor of Medical Oncology, of Centre Oscar Lambret in 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 endometrium." 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. References: (1) Dewar, J et al. The effect of anastrozole (Arimidex) on serum lipids - data from a randomised comparison of anastrozole versus tamoxifen in postmenopausal women with advanced breast cancer. Breast Cancer Research and Treatment. 2000; 64: 51 (Abs 164) (2) Michaud LB, Buzdar AU. Risks and benefits of aromatase inhibitors in postmenopausal breast cancer. Drug Safety 1999; 21: 297-309 (3) Bajetta E et al. Double-blind, randomised, multicentre endocrine trial comparing two letrozole doses, in postmenopausal breast cancer patients. Eur J Cancer 1999; 35: 208-213 (4) L Esparza-Guerra, A Buzdar. Anastrozole (Arimidex) does not impair adrenal cortisol or aldosterone synthesis in postmenopausal women with advanced breast cancer. ASCO, May 2001 SOURCE: AstraZeneca Related Links: Anastrozole (Arimidex) and AstraZeneca.
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