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Are all aromatase inhibitors alike?

Publication ,  Journal Article
Blackwell, KL
Published in: Breast Cancer Res Treat
December 2008

The anti-estrogen tamoxifen was the gold-standard adjuvant therapy for hormone-receptor-positive (HR+) early breast cancer for several decades, but has recently been displaced by the third-generation aromatase inhibitors (AIs). Three AIs are commercially available: letrozole, anastrozole and exemestane. All are more effective and at least as well tolerated as tamoxifen as adjuvant therapy for HR+ breast cancer in postmenopausal women. Despite the wealth of data comparing AIs with tamoxifen, it is unclear whether the three AIs are clinically equivalent, owing to the lack of head-to-head trials directly comparing them. Preclinical and small clinical studies suggest that letrozole is the most potent inhibitor of aromatase, reducing circulating estrogen levels to a greater degree than the other agents. However, whether this greater activity translates into superior clinical efficacy remains to be determined. In the absence of direct comparative data, cross-trial comparisons have been used to gain insights into any safety or efficacy differences. All three AIs have been compared directly with tamoxifen, and efficacy relative to tamoxifen has been compared across trials, although such analyses are complicated by differences in treatment schedules, patient populations and trial designs. Definitive conclusions cannot yet be drawn, but some important differences are coming to light, with upfront letrozole appearing particularly effective at preventing early distant metastasis, an event strongly associated with breast-cancer-related death. No safety differences between the AIs have yet been identified. This article explores the pharmacologic and clinical differences between the AIs, based on data from clinical and preclinical studies.

Duke Scholars

Published In

Breast Cancer Res Treat

DOI

EISSN

1573-7217

Publication Date

December 2008

Volume

112 Suppl 1

Start / End Page

35 / 43

Location

Netherlands

Related Subject Headings

  • Receptors, Progesterone
  • Receptors, Estrogen
  • Oncology & Carcinogenesis
  • Humans
  • Female
  • Breast Neoplasms
  • Aromatase Inhibitors
  • 3211 Oncology and carcinogenesis
  • 3202 Clinical sciences
  • 1112 Oncology and Carcinogenesis
 

Citation

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Blackwell, K. L. (2008). Are all aromatase inhibitors alike? Breast Cancer Res Treat, 112 Suppl 1, 35–43. https://doi.org/10.1007/s10549-008-0233-9
Blackwell, Kimberly L. “Are all aromatase inhibitors alike?Breast Cancer Res Treat 112 Suppl 1 (December 2008): 35–43. https://doi.org/10.1007/s10549-008-0233-9.
Blackwell KL. Are all aromatase inhibitors alike? Breast Cancer Res Treat. 2008 Dec;112 Suppl 1:35–43.
Blackwell, Kimberly L. “Are all aromatase inhibitors alike?Breast Cancer Res Treat, vol. 112 Suppl 1, Dec. 2008, pp. 35–43. Pubmed, doi:10.1007/s10549-008-0233-9.
Blackwell KL. Are all aromatase inhibitors alike? Breast Cancer Res Treat. 2008 Dec;112 Suppl 1:35–43.
Journal cover image

Published In

Breast Cancer Res Treat

DOI

EISSN

1573-7217

Publication Date

December 2008

Volume

112 Suppl 1

Start / End Page

35 / 43

Location

Netherlands

Related Subject Headings

  • Receptors, Progesterone
  • Receptors, Estrogen
  • Oncology & Carcinogenesis
  • Humans
  • Female
  • Breast Neoplasms
  • Aromatase Inhibitors
  • 3211 Oncology and carcinogenesis
  • 3202 Clinical sciences
  • 1112 Oncology and Carcinogenesis