The ATAC adjuvant breast-cancer trial: Six-year results of the endometrial subprotocol

Abstract

Postmenopausal women with localised, early breast cancer (n = 285) were enrolled in a prospective subprotocol of the ‘arimidex, tamoxifen, alone or in combination’ (ATAC) trial to assess gynaecological abnormalities arising during treatment with anastrozole (1 mg/day) or tamoxifen (20 mg/day). After 6 years' follow-up, there appeared to be non-significantly fewer endometrial abnormalities with anastrozole than with tamoxifen (12.4% vs 20.2%, odds ratio 0.52; 95% confidence intervals 0.20, 1.32; p = 0.17). The time to first endometrial abnormality was non-significantly longer for patients receiving anastrozole compared with tamoxifen (hazard ratio 0.57; 95% confidence intervals 0.26, 1.22; p = 0.15), with most abnormalities occurring within the first year of treatment. Fewer patients treated with anastrozole appeared to require medical intervention for endometrial abnormalities, compared with patients on tamoxifen. This study showed that there was no significant difference in endometrial pathology between anastrozole and tamoxifen treatment groups.

Keywords:

• Adjuvant treatment
• anastrozole
• breast cancer
• endometrial abnormalities
• tamoxifen

Acknowledgements

We thank the patients who are participating in the ATAC trial and all the investigators listed inAppendix C. The authors would like to thank Sally Mitchell PhD and Sandra Cuscό PhD from Complete Medical Communications, who provided medical writing support funded by AstraZeneca. The trial sponsor, AstraZeneca, provided support for the conduct of the study, data collection and project management. S. Duffy was the International Coordinating Investigator. All authors participated in the collection, analysis and interpretation of data, took part in writing the report, and read and approved the final version.

Declaration of interest: S. Duffy and M. Wells have received research funding from AstraZeneca. M. Lansdown has received travel grants and honoraria from AstraZeneca, Novartis and Pfizer. G. Clack is an employee of AstraZeneca.