Anastrozole as adjuvant therapy for early-stage breast cancer: implications of the ATAC trial

Clin Breast Cancer. 2003 Apr;4 Suppl 1:S42-8. doi: 10.3816/cbc.2003.s.014.


Tamoxifen has been the gold standard adjuvant therapeutic agent for postmenopausal women with hormone-sensitive breast cancer for > 25 years. Although it continues to play an important role in treating premenopausal women, tamoxifen's association with some serious safety and tolerability issues, including increased incidence of endometrial cancer and thromboembolic events, may be cause to limit its use in postmenopausal women. Anastrozole was the first drug to show improved efficacy and safety compared with standard therapies for first- and second-line therapy of hormone-sensitive advanced breast cancer in postmenopausal women. This article provides a review of the results of the first major analysis of the Arimidex, Tamoxifen, Alone or in Combination (ATAC) early-stage breast cancer trial, initiated in 1996, and discusses the implications for the use of anastrozole in the adjuvant setting. This randomized, double-blind, multicenter trial compared tamoxifen (20 mg once daily) with anastrozole (1 mg) alone and in combination with tamoxifen, as adjuvant endocrine treatment for postmenopausal patients with operable, invasive, early-stage breast cancer. The results of the ATAC trial show anastrozole to be more effective and better tolerated than tamoxifen in this group of patients, and an updated follow-up suggests the therapeutic index for anastrozole will continue to remain superior to that of tamoxifen. Anastrozole is now emerging as a new standard for the adjuvant treatment of postmenopausal women with hormone-sensitive early-stage breast cancer. New adjuvant trials are currently using anastrozole in the control arm.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Review

MeSH terms

  • Age Factors
  • Anastrozole
  • Antineoplastic Agents, Hormonal / administration & dosage*
  • Antineoplastic Agents, Hormonal / adverse effects
  • Antineoplastic Combined Chemotherapy Protocols*
  • Aromatase Inhibitors / administration & dosage*
  • Aromatase Inhibitors / adverse effects
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / pathology
  • Chemotherapy, Adjuvant
  • Disease-Free Survival
  • Double-Blind Method
  • Female
  • Humans
  • Multicenter Studies as Topic
  • Nitriles / administration & dosage*
  • Nitriles / adverse effects
  • Randomized Controlled Trials as Topic
  • Tamoxifen / administration & dosage*
  • Tamoxifen / adverse effects
  • Time Factors
  • Treatment Outcome
  • Triazoles / administration & dosage*
  • Triazoles / adverse effects
  • United States


  • Antineoplastic Agents, Hormonal
  • Aromatase Inhibitors
  • Nitriles
  • Triazoles
  • Tamoxifen
  • Anastrozole