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Pure antiestrogens as a new therapy for breast cancer
1Department of Surgery, Northwestern University Medical School, Chicago, IL 60611, USA.
Abstract:
Tamoxifen is the endocrine therapy of choice for all stages of breast cancer. However, the drug cannot be considered to be a cure as drug resistance will eventually develop. The resistance can take two forms: either the loss of estrogen receptor or the selection of estrogen receptor positive disease that is tamoxifen stimulated for growth. Laboratory studies have demonstrated that tamoxifen-stimulated MCF-7 breast tumors can develop in athymic mice. A number of pure (nonestrogenic) antiestrogens have been discovered that can either be administered by injection (e.g., ICI 182,780) or orally (e.g., EM-800). In preliminary clinical studies, the compound ICI 182,780 (Faslodex) has been shown to be an effective second-line therapy after tamoxifen failure. The goal of future clinical studies is to evaluate the therapeutic efficacy and patient acceptability of aromatase inhibitors (postmenopausal estrogen withdrawal), and injectable or oral pure antiestrogens after the failure of long-term tamoxifen therapy. Clearly, the primary purpose for the treatment of advanced breast cancer is to control disease growth; nevertheless, an evaluation of the effect of new agents on bones and lipids is required before pure antiestrogens could be considered for adjuvant therapy.
Insights
Tamoxifen resistance in breast cancer necessitates new treatments. Pure antiestrogens and aromatase inhibitors show promise as effective alternatives for advanced disease management.
Area of Science:
- Oncology
- Endocrinology
- Pharmacology
Background:
- Tamoxifen is a primary endocrine therapy for breast cancer but resistance develops.
- Resistance mechanisms include estrogen receptor loss or tamoxifen-stimulated growth.
- Novel pure antiestrogens (e.g., ICI 182,780, EM-800) offer alternative treatment strategies.
Purpose of the Study:
- To review the development of resistance to tamoxifen in breast cancer.
- To explore the potential of pure antiestrogens and aromatase inhibitors as future therapies.
- To assess the efficacy and patient acceptability of new agents after tamoxifen failure.
Main Methods:
- Review of laboratory studies on tamoxifen-stimulated tumors.
- Analysis of preliminary clinical data for ICI 182,780 (Faslodex).
- Discussion of future clinical trial goals for novel antiestrogens and aromatase inhibitors.
Main Results:
- Tamoxifen resistance is a significant clinical challenge.
- ICI 182,780 demonstrates efficacy as a second-line therapy post-tamoxifen.
- Further evaluation of aromatase inhibitors and pure antiestrogens is warranted.
Conclusions:
- New therapeutic agents are needed to overcome tamoxifen resistance in advanced breast cancer.
- Pure antiestrogens and aromatase inhibitors represent promising treatment options.
- Comprehensive evaluation of safety (bone, lipid effects) is crucial before adjuvant use.