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Five Years of Adjuvant Treatment With Anastrozole (Arimidex) Shows Better Results Than Tamoxifen in Breast Cancer: Presented at SGOC

By Crystal Phend

ST. GALLEN, SWITZERLAND -- February 2, 2005 -- Postmenopausal women with breast cancer may experience significant improvements in disease-free survival and time to recurrence with the use of adjuvant anastrozole (Arimidex) as compared with tamoxifen.

"Five years of anastrozole therapy should now be considered as the standard of care for postmenopausal women with hormone sensitive early breast cancer," said presenter Anthony Howell, professor, medical oncology cancer research department, Christie Hospital, Manchester, United Kingdom.

Dr. Howell reported the study findings, on behalf of the "Arimidex," Tamoxifen, Alone or in Combination (ATAC) Trialists' Group, during a presentation here on January 28^th at the 9^th International St. Gallen Oncology Conferences: Primary Therapy of Early Breast Cancer.

The ATAC trial randomised 6366 postmenopausal women to 1 of 3 treatment groups, but an initial analysis of the data suggested no efficacy or tolerability benefit to combination treatment so that arm was discontinued.

The final analysis of the multinational, double-blind study included 3125 women on anastrozole and 3116 on tamoxifen over a 5-year period following surgery with or without radiotherapy and chemotherapy. Median follow-up was 68 months.

Both groups had similar patient characteristics; about 60% were node negative and about 63% had a tumour size of less than 2 cm.

In the final analysis, anastrozole had a benefit over tamoxifen that improved over time based on 2 previous analyses. The absolute benefit was 2.9% for disease-free survival and of 3.4% for time to recurrence.

Women with hormone receptor-positive breast cancer received the most benefit from anastrozole treatment with a hazard ratio of 0.83 for disease-free survival and of 0.74 for time to recurrence as compared with 0.87 and 0.79 respectively for the anastrozole group.

Time to distant recurrence was also significantly better in the anastrozole group; however, there was no overall survival advantage.

A previously noted potential treatment interaction with chemotherapy disappeared on final analysis, according to the researchers.

No new tolerability concerns were observed in this analysis, although the absolute incidence of adverse events increased with longer follow-up. Compared to tamoxifen, the anastrozole arm had statistically fewer cases of vaginal bleeding and discharge, endometrial cancer, hot flushes, and thromboembolic and cerebrovascular events.

However, the authors observed a significant increase in fractures and joint symptoms in patients receiving anastrozole.


[Presentation Title: Efficacy Data From the ATAC ('Arimidex', Tamoxifen, Alone or in Combination) Trial After Completion of 5 Years' Adjuvant Treatment." Abstract P127. Safety and Tolerability Data From the ATAC ('Arimidex', Tamoxifen, Alone or in Combination) Trial After Completion of 5 Years' Adjuvant Treatment. Abstract: P128]

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