From the Guidelines
The MammaPrint gene test is indicated for patients with hormone receptor-positive, HER2-negative breast cancer, particularly those with high clinical risk and node-negative or node-positive disease with one to three positive nodes, to inform decisions on withholding adjuvant systemic chemotherapy. This recommendation is based on the American Society of Clinical Oncology (ASCO) clinical practice guideline focused update, which suggests that the MammaPrint assay may be used in patients with high clinical risk to identify those whose outcome is predicted to be sufficiently favorable that chemotherapy is unlikely to provide meaningful benefit 1. The test is most valuable for patients where there is uncertainty about the benefit of adjuvant chemotherapy, and it can help oncologists determine whether chemotherapy should be added to endocrine therapy.
Key Indications for MammaPrint
- Hormone receptor-positive, HER2-negative breast cancer
- Node-negative or node-positive disease with one to three positive nodes
- High clinical risk per MINDACT categorization
- Uncertainty about the benefit of adjuvant chemotherapy
How MammaPrint Works
MammaPrint works by analyzing the activity of 70 genes involved in cancer cell proliferation, invasion, and metastasis, providing prognostic information beyond traditional factors like tumor size, grade, and lymph node status. Results typically take 7-10 days and can significantly impact treatment planning by potentially sparing low-risk patients from unnecessary chemotherapy while ensuring high-risk patients receive appropriate treatment.
Limitations and Considerations
The MINDACT study, which evaluated the MammaPrint assay in 6,693 women with early-stage breast cancer, had several limitations, including a lack of power to detect a significant difference in favor of chemotherapy and limited follow-up for patients with node-positive disease 1. Therefore, the test should be used with caution in patients with two to three positive nodes, and patients should be informed that a benefit from chemotherapy cannot be excluded. Additionally, the utility of the MammaPrint assay in patients with lymph node–positive disease assessed at low clinical risk per MINDACT categorization is not clear, and the test is not recommended for routine use in these patients.
From the Research
Indications for MammaPrint Gene Test in Breast Cancer
The MammaPrint gene test is used to determine the risk of recurrence in breast cancer patients. The indications for this test are as follows:
- Estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative, and 1 to 3 node-positive invasive breast cancer 2
- Hormone receptor-positive (HR+)/HER2-negative breast cancer, particularly for those with high-risk MammaPrint scores 3, 4, 5
- Luminal early breast cancer, where the test results can impact treatment decisions 4, 5
- Early-stage breast cancer patients, where the test can guide therapy decisions 5
Key Factors Associated with MammaPrint Risk Group
The following factors are associated with the low MammaPrint risk group:
- Low histologic grade 2
- Progesterone receptor-positivity 2
- Low Ki-67 2
- Peritumoral edema absence 2
- High proportion of persistent components 2
Impact of MammaPrint on Treatment Decisions
The MammaPrint test results can significantly impact treatment decisions in breast cancer patients:
- Change in treatment decision in 24.0% of patients after receiving MammaPrint results 5
- Removal of chemotherapy from treatment recommendation in 71.0% of low-risk patients initially prescribed chemotherapy 5
- Addition of chemotherapy to treatment recommendation in 65.1% of high-risk patients not initially prescribed chemotherapy 5
- High adherence to genetically determined risk assessment, representing a key prerequisite for achieving a personalized cost-effective approach to disease management of early breast cancer 4