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Updated: Jul 12, 2026

Systems Biology of Metabolic Regulation by Estrogen Receptor Signaling in Breast Cancer
Published on: March 17, 2016
Application of aromatase inhibitors in endocrine responsive breast cancers
1Massachusetts General Hospital, 55 Fruit Street, LRH 302, Boston, MA 02114, USA. pgoss@partners.org
Abstract:
Aromatase (estrogen synthetase) inhibitors (AIs) have been incorporated into adjuvant treatment of early-stage breast cancer in post-menopausal women and their role in pre-menopausal is being investigated. Several questions regarding AIs remain unanswered: optimal sequence with tamoxifen; optimal duration and the best agent in the class. The benefits of extending therapy beyond 5 years has been established by the MA17 trial and many follow-on trials are exploring prolonged therapy. Several strategies to overcome de novo and acquired resistance are being explored. Improving on the "total estrogen blockade" by adding fulvestrant is one example; blocking collaborating cell signaling pathways is another. Candidate targets for this include the erbB2, IGF1R and the mTOR cell survival pathway. Identification of both host (pharmacogenomic) and tumor (genomic) signatures as prognostic and predictive factors will help to select patients for appropriate therapies in the future and reduce the number needed to treat to benefit a few.
Insights
Aromatase inhibitors are key in breast cancer treatment for post-menopausal women. Research is ongoing to optimize their use, duration, and effectiveness, especially in pre-menopausal women and in overcoming resistance.
Area of Science:
- Oncology
- Endocrinology
- Pharmacology
Background:
- Aromatase inhibitors (AIs) are standard adjuvant therapy for early-stage breast cancer in post-menopausal women.
- The role of AIs in pre-menopausal women is under investigation.
- Unanswered questions include optimal sequencing with tamoxifen, duration, and agent selection.
Purpose of the Study:
- To review the current status and future directions of aromatase inhibitor therapy in breast cancer.
- To explore strategies for overcoming de novo and acquired resistance to AIs.
- To highlight the potential of pharmacogenomic and genomic signatures for personalized therapy.
Main Methods:
- Review of clinical trial data, including the MA17 trial and its follow-on studies.
- Exploration of novel therapeutic strategies, such as combining AIs with fulvestrant or targeting cell signaling pathways (erbB2, IGF1R, mTOR).
- Discussion of the role of biomarkers in patient selection.
Main Results:
- Extended AI therapy beyond 5 years shows benefits, with ongoing trials exploring prolonged durations.
- Strategies to overcome resistance include enhancing estrogen blockade and targeting collaborating pathways.
- Pharmacogenomic and genomic signatures are emerging as predictive factors.
Conclusions:
- Further research is needed to define optimal AI treatment paradigms.
- Personalized medicine approaches using biomarkers will be crucial for selecting patients and improving treatment outcomes.
- Targeting resistance mechanisms and optimizing drug combinations hold promise for enhancing efficacy.
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