Clinical differences among the aromatase inhibitors

Area of Science:

• Oncology
• Pharmacology

Background:

• Three third-generation aromatase inhibitors (anastrozole, letrozole, exemestane) are available in the U.S.
• These agents differ in structure, metabolism, and aromatase suppression efficacy.
• Clinical significance of these differences remains under investigation.

Purpose of the Study:

• To explore the efficacy and tolerability of third-generation aromatase inhibitors.
• To compare these agents in both metastatic and adjuvant breast cancer settings.

Main Methods:

• Review of clinical trial data comparing aromatase inhibitors to megesterol acetate and tamoxifen.
• Analysis of Phase III trials in metastatic breast cancer.
• Examination of early results from adjuvant setting trials, including the ATAC trial.

Main Results:

• Anastrozole, letrozole, and exemestane are equivalent or superior to megesterol acetate in second-line metastatic breast cancer therapy.
• Anastrozole and letrozole are equivalent or superior to tamoxifen in first-line metastatic breast cancer.
• Early ATAC trial data suggests anastrozole offers a slight disease-free survival benefit over tamoxifen in the adjuvant setting.

Conclusions:

• Third-generation aromatase inhibitors represent effective treatment options for metastatic breast cancer.
• Further follow-up is required to fully establish the role of aromatase inhibitors in adjuvant breast cancer therapy.