A genomic assay is a type of test that uses a sample of the breast cancer tissue to analyze the activity of a group of genes, rather than just a single gene. Genes contain the recipes for the various proteins a cell needs to stay healthy and function normally. Knowing whether certain genes are present or absent, overly active or not active enough, can help doctors predict the risk of the breast cancer returning later. This can be helpful in making treatment decisions, such as whether or not chemotherapy should be part of the treatment plan.
Three genomic assays are currently in use for breast cancer: Oncotype DX, MammaPrint, and Mammostrat. While all three tests are somewhat similar, there are differences:
- The Oncotype DX test is used to estimate a woman’s risk of recurrence of early-stage, hormone-receptor-positive breast cancer, as well as how likely she is to benefit from chemotherapy after breast cancer surgery. The Oncotype DX test also is used to estimate a woman’s recurrence risk of DCIS (ductal carcinoma in situ) and/or the risk of a new invasive cancer developing in the same breast, as well as how likely she is to benefit from radiation therapy after DCIS surgery. The Oncotype DX test analyzes the activity of 21 genes and then calculates a recurrence score number between 0 and 100; the higher the score, the greater the risk of recurrence.
- The MammaPrint test is used to estimate a women’s recurrence risk for early-stage breast cancer. The breast cancer can be hormone-receptor-positive or hormone-receptor-negative. The MammaPrint test analyzes 70 genes to see how active they are and then calculates either a high-risk or a low-risk recurrence score. MammaPrint results can help a woman and her doctor make a more informed decision about whether to use chemotherapy to reduce recurrence risk.
- The Mammostrat test is used to estimate a woman’s risk of recurrence of early-stage, hormone-receptor-positive breast cancer. The Mammostrat test measures the levels of five genes in breast cancer cells. These measurements are used to calculate a risk index score. The higher the risk index, the more likely the cancer is to come back. Women are assigned to a risk category (high, moderate, or low) based on their risk index score.
Doctors do not automatically order one of these tests for every person with breast cancer. Instead, they typically reserve these tests for patients who (1) have early-stage breast cancer that has not traveled to the lymph nodes, or to just a few; or (2) in the case of Oncotype DX have DCIS. If you fit these criteria, you and your doctor can determine whether genomic testing is right for you. All three tests can be done as part of the initial pathology testing or as a separate test ordered days, weeks, or even months later on the original tissue sample.
Whichever test you have, you and your doctor will consider your scores in combination with the other information in your pathology report, such as:
- size and grade of the cancer
- hormone receptor protein levels
- whether cancer cells were found in nearby lymph nodes
to come up with a treatment plan for you.
Learn more about Oncotype DX.
Learn more about MammaPrint.
Learn more about Mammostrat.