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Arimidex (Anastrozole) Continues to Show Benefits Over Tamoxifen in Early-stage Breast Cancer: Presented at SABCS

By Charlene Laino

SAN ANTONIO, TX -- December 12, 2002 -- Updated results from the ongoing Arimidex, Tamoxifen, Alone or in Combination (ATAC) trial continue to suggest that anastrozole is superior to tamoxifen in the treatment of postmenopausal women with early-stage breast cancer.

Principal United States Investigator Aman Buzdar, MD, a professor in the Department of Breast Medical Oncology at the University of Texas M.D. Anderson Cancer Center in Houston, Texas, United States, presented the data here on December 11^th at the 25^th Annual San Antonio Breast Cancer Symposium (SABCS).

The results of the ATAC trial main analysis were reported in full at last year's SABCS. That analysis showed that at a median follow-up of 33.3 months, 89.4 percent of women given anastrozole were disease free, compared with 87.4 percent of women given tamoxifen -- an absolute difference of 2.0 percent.

On the basis of that analysis, the U. S. Food and Drug Administration approved anastrozole (Arimidex®, AstraZeneca) for the adjuvant treatment of early-stage breast cancer in postmenopausal women with hormone receptor-positive disease.

The updated analysis shows that the absolute difference in disease-free survival continues to increase over time, Dr. Buzdar said. At a median follow-up of 47 months, 86.9 percent of women given anastrozole were disease free, compared with 84.5 percent of those given tamoxifen -- a difference of 2.4 percent (p=0.030).

Among women with confirmed hormone-sensitive tumours, the absolute difference in disease-free survival was even higher: 89.0 percent vs. 86.1 percent (p=0.014).

Anastrozole is an orally active nonsteroidal agent that inhibits the aromatase enzyme, thereby suppressing oestrogen levels.

The ATAC trial was designed to compare the efficacy and safety of anastrozole alone, tamoxifen alone and the combination of anastrozole and tamoxifen as adjuvant treatment for postmenopausal women with early-stage breast cancer, following primary therapy. The combination arm has since been terminated, as the results were comparable to those in the tamoxifen-only arm, Dr. Buzdar said.

The trial enrolled more than 9,000 patients who were randomised to one of the three treatment arms; all arms received treatment for five years. Eligible patients were postmenopausal women with histologically proven, operable invasive breast cancer who had completed treatment with primary surgery and chemotherapy. All were aged 45 years or older.

The analysis also showed that anastrozole achieved a greater time to recurrence and a lower risk of contralateral breast cancer than tamoxifen.

While safety data will not be presented until later this week, Dr. Buzdar said, "There are no surprises." Last year's analysis showed that anastrozole was associated with a lower incidence of thromboembolic events and endometrial cancer, while tamoxifen was associated with a lower risk of musculoskeletal disorders and fractures.

On the basis of these results, " Arimidex® should be considered a better choice of therapy for postmenopausal women with hormone-sensitive early breast cancer," Dr. Buzdar said.

Nevertheless, he stressed, the ultimate choice should be the patient's: "I sit down with each woman and explain the options, the benefits and risks of each treatment. Nine in ten women will want the newer drug. But some will want the drug that's been around 30 years."

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