New Data Confirm Benefit Of Extended Adjuvant Treatment With Arimidex (Anastrozole)

Main Category: Breast Cancer
Also Included In: Cancer / Oncology
Article Date: 19 Dec 2007 - 4:00 PDT

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New data published in the Journal of the National Cancer Institute(JNCI) demonstrate the significant benefits of extended adjuvant treatment with Arimidex (anastrozole) for postmenopausal women who have completed five years of treatment with tamoxifen for hormone receptor-positive early breast cancer.

Currently the standard duration of endocrine treatment for these patients is five years. This latest report demonstrates the safety and efficacy of Arimidex in the extended adjuvant setting, and adds to the ongoing debate as to "what the optimal duration of adjuvant endocrine therapy should be?" The new data supports extension of the current five-year treatment cycle with Arimidex to give women additional protection against the risk of recurrence.

The Austrian Breast and Colorectal Cancer Study Group (ABCSG) 6a study, involving 856 patients, was designed to investigate the effect of extending adjuvant therapy with Arimidex for postmenopausal women with hormone receptor-positive early breast cancer after five years of tamoxifen. The study showed that women who received Arimidex (n=387) rather than no further treatment (n=469) experienced:1

- A 38% reduction in the risk of recurrence (HR = 0.62, 95% CI = 0.40-0.96, P=0.031)
- A 47% reduction in the risk of distance metastasis (HR = 0.53, 95%CI = 0.29 - 0.96, P=0.034)
- No unexpected adverse events

Professor Michael Gnant, President of the ABCSG, Vienna, Austria commented, "While the best available treatment should be offered at the earliest opportunity in order to reduce the risk of recurrence and minimise life-threatening side effects, these data confirm that women can be given Arimidex later in the treatment cycle, to extend their chance of living cancer-free for longer."

Professor Raimund Jakesz, Department of Surgery, Medical University of Vienna, Vienna, Austria added, "I welcome these new data because they show that Arimidex can further reduce the risk of recurrence in women with hormone receptor-positive early breast cancer who have completed their five-year adjuvant treatment."

Treatment strategies for early breast cancer have changed significantly in recent years. The introduction of aromatase inhibitors (AIs) such as Arimidex, which have proved to be not only more effective but better tolerated than tamoxifen, has led to international guidelines now recommending that all postmenopausal women with hormone receptor-positive early breast cancer should receive an AI at some point during their treatment to reduce the risk of disease recurrence.2,3

Although, as this latest study shows, patients benefit from extending adjuvant therapy with Arimidex on completion of tamoxifen, other trials indicate earlier use may be more effective in helping women remain disease-free.

The landmark Arimidex, Tamoxifen, Alone or in Combination (ATAC) study confirmed the superior efficacy and tolerability profile of Arimidex compared with tamoxifen given for five years to postmenopausal women with newly diagnosed hormone-sensitive early breast cancer.4Arimidex has now overtaken tamoxifen as the most widely prescribed treatment in this patient group.

For patients already being treated with tamoxifen, data highlight they can still benefit from Arimidex. A recent analysis of the Arimidex-'Nolvadex' 95 (ARNO 95) study showed that postmenopausal women who have been treated with tamoxifen for two to three years for hormone-sensitive early breast cancer also benefit by switching to Arimidex rather than continuing on tamoxifen treatment.5

Of note, NSABP Trial B-14 indicated that there is no additional advantage for continuation of tamoxifen beyond 5 years6. These latest findings from the ABCSG 6a study add to the increasing body of evidence that Arimidex is a superior adjuvant treatment to tamoxifen for early breast cancer in the extended adjuvant setting. Arimidex is now the only AI that has been proven to benefit women at all stages of early breast cancer, whichever treatment regimen is employed.

References

1. Jakesz R, et al. Extended Adjuvant Therapy with Anastrozole among Postmenopausal Breast Cancer Patients: Results from the Randomized Austrian Breast and Colorectal cancer Study Group Trial 6a. JNCI 2007; 12 December.

2. 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 (3): 1-11.

3. NCCN Clinical Practice Guidelines in Oncology™ - Breast Cancer (V2) 2007. Please click here.

4. 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): 60-2.

5. Kaufmann M, Jonat W, Hilfrich J, et al. Improved Overall Survival in Postmenopausal Women With Early Breast Cancer After Anastrozole Initiated After 2 Years of Treatment With Tamoxifen Compared With Continued Tamoxifen: The ARNO 95 Study. J Clin Onc2007 (Early online publication). Please click here.

6. Fisher B, Dignam J, Bryant J, Wolmark N. Five versus more than five years of tamoxifen for lymph node-negative breast cancer: Updated findings from the National Surgical AdjuvantBreast and Bowel Project B-14 randomized trial. Journal of the National Cancer Institute 2001;93 (9):684-90.

ABCSG 6a trial design

ABCSG 6a was a prospective randomised, open, clinical study designed as a continuation of the ABCSG 6 trial which compared adjuvant treatment with either 5 years of tamoxifen alone, or 5 years of adjuvant tamoxifen plus aminoglutethimide for the first 2 years of treatment. Any patient in the ABCSG 6 study who had not experienced recurrence by the end of 5 years of adjuvant therapy was eligible to be re-randomised into ABCSG 6a, to receive either anastrozole (1mg daily) or no treatment for a further 3 years, starting within 6 weeks of completing 5 years of tamoxifen.

Other extended adjuvant trial data

The MA-17 study was conducted by Novartis to investigate extended adjuvant therapy with letrozole in postmenopausal women with receptor-positive or receptor-unknown early breast cancer who were disease-free after completing five years of adjuvant tamoxifen therapy.

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