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Abstract:
In estrogen target tissues and hormone-dependent tumors, the steroid enters the cells and binds to a cytoplasmic protein called the estrogen receptor (ER). The steroid-receptor complex then migrates to the nuclei, where it initiates the biochemicial events characteristic of estrogen stimulation. Since ER is absent in tissues not responsive to estrogen, recent studies have asked whether ER assays in human breast cancer tissue might be used to identify those patients likely to respond to endocrine therapy. Data on 436 clinical trials contributed from a dozen centers around the world now clearly indicate that if a patient's tumor does not contain ER, there is virtually no chance of tumor regression following endocrine therapy. A large number of patients can be thus spared unrewarding major endocrine ablative therapy if ER assays are performed routinely. Of tumors with positiev ER, 55-60% respond to endocrine therapy. This single piece of data, when coupled with available clinical prognostic factors such as menopausal status, disease free interval, site of the dominant lesion, and especially response to previous hormonal therapies, should be practicing oncologist to select or reject endocrine therapy with considerable confidence.
Insights
Estrogen receptor (ER) assays in breast cancer tissue predict response to endocrine therapy. Tumors lacking ER show no regression, sparing patients unnecessary treatment.
Area of Science:
- Oncology
- Endocrinology
- Molecular Biology
Background:
- Estrogen receptor (ER) mediates estrogenic effects in target tissues and hormone-dependent tumors.
- ER presence within tumor cells is crucial for initiating biochemical events characteristic of estrogen stimulation.
- ER absence in non-responsive tissues suggests its role in predicting treatment outcomes.
Purpose of the Study:
- To evaluate the utility of ER assays in human breast cancer tissue for identifying patients likely to respond to endocrine therapy.
- To determine the predictive value of ER status for endocrine therapy efficacy.
Main Methods:
- Analysis of data from 436 clinical trials across multiple international centers.
- Routine ER assays performed on human breast cancer tissue samples.
Main Results:
- Tumors lacking ER demonstrated virtually no chance of regression following endocrine therapy.
- Approximately 55-60% of ER-positive tumors responded to endocrine therapy.
- ER assay results, combined with clinical prognostic factors, aid in selecting or rejecting endocrine therapy.
Conclusions:
- Routine ER assays are essential for sparing patients from ineffective endocrine ablative therapy.
- ER status is a critical determinant of response to endocrine therapy in breast cancer.
- Integrating ER assay data with clinical factors enhances treatment selection for breast cancer patients.