The role of aromatase inhibitors as adjuvant therapy for early breast cancer in postmenopausal women

Eur J Cancer. 2005 Aug;41(12):1678-89. doi: 10.1016/j.ejca.2004.10.020. Epub 2004 Nov 25.


For endocrine therapy of hormone-sensitive advanced breast cancer in postmenopausal women, the third-generation aromatase inhibitors, letrozole, anastrozole, and exemestane, are effective both as alternatives to tamoxifen in first-line treatment and following first-line tamoxifen failure. These three agents are currently being evaluated as adjuvant therapy of early breast cancer, again relative to the standard, tamoxifen. Three treatment strategies are under investigation: replacement of tamoxifen as adjuvant therapy for 5 years (early adjuvant therapy); sequencing of tamoxifen before or after an aromatase inhibitor during the first 5 years (early sequential adjuvant therapy); or following 5 years of tamoxifen (extended adjuvant therapy). Results of the first early adjuvant trial (Arimidex, Tamoxifen Alone or in Combination [ATAC]) demonstrated that anastrozole was significantly more effective than tamoxifen in reducing the risk of disease recurrence. Two trials sequencing 2-3 years of an aromatase inhibitor after 2-3 years of tamoxifen have also reported results. A large trial (International Collaborative Cancer Group [ICCG] trial 96) found switching to exemestane to be significantly superior to continuing on tamoxifen in disease-free survival, and in a small study (Italian Tamoxifen Arimidex [ITA] trial), similarly sequencing anastrozole after tamoxifen significantly reduced the hazard of recurrence compared with remaining on tamoxifen. Extended adjuvant therapy with 5 years of letrozole versus placebo following 5 years of tamoxifen was evaluated in the MA.17 trial. Compared with placebo, letrozole resulted in a significant improvement in disease-free survival that was irrespective of whether patients had lymph node-positive or -negative tumours. Results of these four trials emphasise the important role of aromatase inhibitors in the adjuvant setting, yet the optimal approach still needs to be defined. A number of trials further evaluating the three adjuvant treatment strategies are ongoing.

Publication types

  • Review

MeSH terms

  • Antineoplastic Agents, Hormonal / therapeutic use*
  • Aromatase Inhibitors / therapeutic use*
  • Breast Neoplasms / drug therapy*
  • Chemotherapy, Adjuvant
  • Clinical Trials, Phase III as Topic
  • Disease-Free Survival
  • Female
  • Humans
  • Multicenter Studies as Topic
  • Neoplasm Recurrence, Local / etiology
  • Postmenopause
  • Randomized Controlled Trials as Topic
  • Tamoxifen / therapeutic use*
  • Treatment Outcome


  • Antineoplastic Agents, Hormonal
  • Aromatase Inhibitors
  • Tamoxifen