Aromatase Inhibitors for Breast Cancer: Proven Efficacy Across the Spectrum of Disease

Clin Breast Cancer. 2008 Feb;8(1):50-64. doi: 10.3816/CBC.2008.n.003.


For more than 100 years, hormonal therapy has been known to be effective in the treatment of breast cancer. Initially, this therapy was dominated by the selective estrogen receptor antagonists such as tamoxifen. Aromatase inhibitors (AIs) are a distinct drug class with demonstrated activity in the treatment of hormone-sensitive breast cancer. All 3 third-generation AIs, exemestane, anastrozole, and letrozole, have been studied in multiple lines of therapy in advanced breast cancer and have demonstrated equivalence or superiority compared with tamoxifen. While initially developed as a treatment option for advanced disease, the AIs have also shown efficacy in the treatment of curable disease, including the neoadjuvant and adjuvant settings. In addition, the AIs demonstrate a tolerable side effect profile in comparison with tamoxifen, and this has led to their early incorporation as standard of care therapy. Given the proven efficacy of AIs across the spectrum of breast cancer, the remaining questions include definitive sequencing strategy, timing, and duration of use. Ongoing trials include head-to-head comparisons between the AIs in early-stage breast cancer; the results of these trials are eagerly anticipated and should further optimize the use of AIs.

Publication types

  • Review

MeSH terms

  • Anastrozole
  • Androstadienes / therapeutic use
  • Aromatase Inhibitors / therapeutic use*
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / pathology
  • Female
  • Humans
  • Letrozole
  • Neoadjuvant Therapy
  • Neoplasm Staging
  • Nitriles / therapeutic use
  • Tamoxifen / therapeutic use*
  • Treatment Outcome
  • Triazoles / therapeutic use


  • Androstadienes
  • Aromatase Inhibitors
  • Nitriles
  • Triazoles
  • Tamoxifen
  • Anastrozole
  • Letrozole
  • exemestane