Genomic Assays in Breast Cancer: Key Differences, Clinical Utility, and Test Selection

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.