According to results recently presented at the 2006 annual San Antonio Breast Cancer Symposium, Aromasin® (exemestane) and Faslodex® (fulvestrant) demonstrate similar efficacy and safety among postmenopausal women who have previously been treated with non-steroidal aromatase inhibitors.
Aromatase inhibitors are drugs that block the production of estrogen. They suppress estrogen levels in postmenopausal women and can slow or stop the growth of estrogen-dependent breast cancer.
Based on how they work, aromatase inhibitors are classified as either steroidal or non-steroidal. Arimidex® (anastrozole) and Femara® (letrozole) are non-steroidal aromatase inhibitors. Aromasin is a steroidal aromatase inhibitor. There is some evidence that patients who stop responding to one type of aromatase inhibitor may respond to the other type.
Faslodex is another type of hormonal therapy drug.Faslodex binds to estrogen receptors so that estrogen is crowded out and no longer able to bind to the receptors. In addition, Faslodex degrades the estrogen receptors to which it is bound. Both of these mechanisms prevent cancer cells from accessing enough estrogen for cellular growth and replication.
To assess the effects of Aromasin and Faslodex in women who have stopped responding to treatment with a non-steroidal aromatase inhibitor, researchers from the United States, Canada, and Europe recently conducted a Phase III clinical trial known as the EFFECT trial.
The study included nearly 700 postmenopausal women with hormone receptor-positive, advanced breast cancer that worsened or recurred during or shortly after treatment with a non-steroidal aromatase inhibitor.
- Time to cancer progression was 3.7 months in both treatment groups.
- A reduction in detectable cancer occurred in 6.7% of patients treated with Aromasin and 7.4% of patients treated with Faslodex.
- There were no significant differences between treatment groups in treatment safety or adverse treatment effects.
The researchers concluded that either Aromasin or Faslodex may be used in postmenopausal women with hormone-positive, advanced breast cancer who have received prior treatment with a non-steroidal aromatase inhibitor. There do not appear to be any significant differences between these two agents in this patient population.
Reference: Gradishar W, Chia S, Piccart-Gebhart J, et al. Fulvestrant versus exemestane following prior non-steroidal aromatase inhibitor therapy: first results from EFECT, a randomized, Phase III trial in postmenopausal women with advanced breast cancer. Proceedings from the 2006 annual San Antonio Breast Cancer Symposium. Oral presentation December 15, 2006. Abstract #12.