Anastrozole (Arimidex) in clinical practice versus the old 'gold standard', tamoxifen
1Department of Breast Medical Oncology, Box 424, University of Texas MD Anderson Cancer Center, 1515 Holcolme Blvd, Houston, TX 77030, USA. abuzdar@mdanderson.org
Abstract:
For the past 25 years, the estrogen antagonist tamoxifen has been considered the 'gold standard' for the treatment of breast cancer, despite certain tolerability issues and the risk of developing resistance. The aromatase inhibitors work by blocking the conversion of androgens to estrogen and were developed for use in patients where ovarian function had ceased (naturally, surgically or pharmacologically). Anastrozole, a third-generation nonsteroidal aromatase inhibitor that is a highly potent and selective inhibitor of the aromatase enzyme, has been shown to be superior to the gold standard tamoxifen for the first-line treatment of postmenopausal women with advanced breast cancer. As second-line therapy, anastrozole has shown superior survival compared with megestrol acetate and is also efficacious as neoadjuvant treatment in postmenopausal women and in combination with goserelin for the treatment of premenopausal women with advanced breast cancer. More recently, the results of the ATAC (anastrozole, tamoxifen, alone or in combination) trial, a large study in 9366 patients, demonstrated that anastrozole was significantly superior to tamoxifen for the treatment of postmenopausal women with early breast cancer, with regards to disease-free survival (p = 0.013) and incidence of contralateral breast cancer (p = 0.007). In addition, anastrozole was shown to be significantly better tolerated than tamoxifen with respect to endometrial cancer (p = 0.02), vaginal bleeding/discharge (p < 0.0001 for both), ischaemic cerebrovascular events (p = 0.0006), thromboembolic events (p = 0.0006) and hot flushes (p < 0.0001), while tamoxifen was associated with significantly less musculoskeletal disorders and fractures than anastrozole (p < 0.0001 for both). This review focuses on both the clinical pharmacology and the clinical data of anastrozole with emphasis on its future applications.
Insights
Anastrozole, a potent aromatase inhibitor, offers superior efficacy and tolerability compared to tamoxifen for postmenopausal breast cancer treatment. It shows improved disease-free survival and fewer adverse events, establishing it as a key therapy.
Area of Science:
- Oncology
- Pharmacology
Background:
- Tamoxifen, an estrogen antagonist, was the standard breast cancer treatment for 25 years.
- Aromatase inhibitors block estrogen production and were developed for postmenopausal patients.
- Anastrozole is a potent, selective, third-generation nonsteroidal aromatase inhibitor.
Purpose of the Study:
- To review the clinical pharmacology and data of anastrozole.
- To emphasize future applications of anastrozole in breast cancer treatment.
Main Methods:
- Review of clinical data and pharmacology of anastrozole.
- Analysis of results from the ATAC trial (anastrozole, tamoxifen, alone or in combination) involving 9366 patients.
Main Results:
- Anastrozole demonstrated superiority over tamoxifen in first-line treatment of advanced breast cancer in postmenopausal women.
- The ATAC trial showed anastrozole significantly improved disease-free survival and reduced contralateral breast cancer incidence compared to tamoxifen.
- Anastrozole exhibited better tolerability than tamoxifen, with fewer adverse events like endometrial cancer and thromboembolic events, although tamoxifen was associated with fewer musculoskeletal issues.
Conclusions:
- Anastrozole is a superior and better-tolerated alternative to tamoxifen for postmenopausal women with early and advanced breast cancer.
- Anastrozole shows efficacy in various settings, including neoadjuvant therapy and combination treatment for premenopausal women.
- Further research into the future applications of anastrozole is warranted.
