Genomic Testing in Breast Cancer: Clinical Applications and Best Practices - Episode 4
Genomic Assays in Breast Cancer: Key Differences, Clinical Utility, and Test Selection
Panelists discuss how they primarily use the 21-gene assay (Oncotype DX) for estrogen receptor–positive (ER+), HER2-negative (HER2–) breast cancers with minimal nodal disease due to its robust data from multiple trials, whereas other assays such as the Breast Cancer Index (BCI) are better for evaluating extended endocrine therapy benefits.
Comparing Available Genomic Assays
Main Discussion Topics:
- Differentiating factors between various genomic assays (Oncotype DX, MammaPrint, EndoPredict, Prosigna Breast Cancer Assay, BCI)
- Considerations for selecting the appropriate test for ER+/HER2– breast cancer
- Specific clinical scenarios where different assays may be preferred
Key Points for Physicians:
- The 21-gene assay (Oncotype DX) is preferred for ER+/HER2– breast cancers with negative or minimal nodal involvement due to robust supporting clinical trial data.
- BCI is valuable for assessing extended endocrine therapy benefit.
- The 70-gene assay (MammaPrint) may be useful for specific clinical trials and some HER2+ cases.
Notable Insights:
- Oncotype DX is supported by extensive clinical data (>80 trials/registries involving ~100,000 patients) and has been incorporated into staging systems.
- Test selection should be driven by the specific clinical question being addressed.
Clinical Significance: Although the 21-gene assay remains the most widely validated option for ER+/HER2– breast cancer, physicians should consider the specific clinical context and question when selecting between available genomic testing options.
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