Genomic tests like MammaPrint and Oncotype DX offer insights after an early-stage breast cancer diagnosis. They help patients and doctors make informed decisions about including chemotherapy in their treatment plan. Understanding the differences between these assays is important for personalized breast cancer care.
The Purpose of Genomic Testing in Early-Stage Breast Cancer
Traditional breast cancer pathology relies on characteristics like tumor size, grade, and the presence of hormone receptors (estrogen receptor, progesterone receptor) and HER2 protein. Genomic tests extend this analysis by examining specific gene activity within tumor cells. This helps predict how a cancer might behave.
Genomic tests provide both prognostic and predictive information. Prognostic insights indicate the likelihood of cancer returning, while predictive information suggests how likely it is to respond to a specific treatment, such as chemotherapy or hormone therapy. Integrating these genomic details with traditional pathology allows for a personalized approach, tailoring treatments to individual tumor biology.
Underlying Science and Genes Analyzed
Oncotype DX analyzes a panel of 21 genes (16 cancer-related, 5 reference) to assess tumor biology. These genes are involved in cellular processes, including cell proliferation, estrogen signaling, and HER2 expression. The test utilizes reverse transcription-polymerase chain reaction (RT-PCR) to measure gene activity.
MammaPrint examines the activity of 70 genes relevant to cancer progression and metastasis. This test employs microarray technology to analyze the gene expression profile. The 70 genes primarily focus on proliferation, but also include genes associated with invasion, angiogenesis, and stromal integrity. Both tests evaluate different gene panels, aiming to assess the tumor’s biological aggressiveness and potential for spread.
Who is Eligible for These Tests
Oncotype DX is primarily used for patients diagnosed with estrogen receptor-positive (ER+), HER2-negative breast cancer. It is validated for individuals with node-negative disease and up to three positive lymph nodes. This helps guide treatment decisions across a significant portion of early-stage breast cancer cases.
MammaPrint is indicated for patients with Stage I or Stage II invasive breast cancer. Eligible tumors are generally 5 centimeters or less, and the test applies to cases with no lymph node involvement or up to three positive lymph nodes. MammaPrint is approved for both ER-positive and ER-negative tumors, although it is most frequently utilized in the ER-positive setting to inform treatment choices.
Understanding the Test Results
The Oncotype DX test provides a “Recurrence Score” (0-100). This score categorizes a patient’s risk of recurrence as low, intermediate, or high. Score thresholds guiding chemotherapy recommendations can vary based on a patient’s age and menopausal status, as highlighted by the TAILORx clinical trial. For instance, certain intermediate scores in younger women might warrant a different consideration for chemotherapy compared to older women.
MammaPrint provides a binary result: “Low Risk” or “High Risk” of distant recurrence (typically within 5 to 10 years). A “Low Risk” result suggests a favorable prognosis, while a “High Risk” indicates a greater likelihood of the cancer spreading. The MammaPrint test can also be used with BluePrint, which provides molecular subtyping information, though its primary focus remains binary risk assessment.
How the Tests Guide Treatment Choices
The results from these genomic tests directly inform decisions about adjuvant chemotherapy following surgery. A “Low Risk” MammaPrint result or a low Oncotype DX Recurrence Score indicates that the cancer has a minimal chance of returning and that the patient would likely not benefit from chemotherapy. In such cases, hormone therapy alone is often sufficient to reduce recurrence risk.
Conversely, a “High Risk” MammaPrint result or a high Oncotype DX Recurrence Score suggests a greater likelihood of recurrence, indicating chemotherapy could provide a substantial benefit. Landmark clinical trials, such as TAILORx for Oncotype DX and MINDACT for MammaPrint, have provided the evidence base for these recommendations. For example, the MINDACT trial demonstrated that nearly half of patients considered high risk by traditional clinical factors, but classified as low risk by MammaPrint, could safely avoid chemotherapy without compromising their outcomes.