Genomic Tests in Early-Stage Breast Cancer
Genomic assays currently used to assess the risk of recurrence in early-stage breast cancer are tests that look at the level of activity in groups of genes in cancer cells to determine how a cancer is likely to recur and respond to treatment.
There are many different genomic assays. Oncotype DX and MammaPrint are the two most common.
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Oncotype DX can be used for people who have stage I or II breast cancer that is hormone receptor-positive and HER2-negative. This genomic assay is part of standard treatment guidelines by the National Comprehensive Cancer Network (NCCN) and by the American Society of Clinical Oncology (ASCO).
This test uses a tumor tissue sample to look at activity patterns in 21 genes. It then scores the chances of recurrence within 10 years. It also predicts whether you are likely to benefit from chemotherapy.
Oncotype DX can be done on tissue samples that were preserved after a biopsy, lumpectomy or mastectomy. Your pathologist will select a sample and will send it to a central lab for testing. Your results should arrive 10 to 14 days later. The possible results are:
- Recurrence Score 0 to 17: You have a low risk for distant recurrence within 10 years if you take 5 years of hormonal therapy. The benefit of adding chemotherapy is likely to be very small.
- Recurrence Score 18 to 31: You have an intermediate risk of distant recurrence in the next 10 years if you take 5 years of hormonal therapy. It is uncertain whether adding chemotherapy will benefit you. Researchers are studying the role of chemotherapy in intermediate scorers.
- Recurrence Score 32 to 100: You are at high risk for distant recurrence within 10 years. The cancer is very likely to respond to chemotherapy treatment. Your doctors will recommend both chemotherapy and hormonal therapy.
There is also an Oncotype DX for ductal carcinoma in situ, or DCIS. This test can be used for people who have DCIS that is hormone receptor-positive and can be removed with lumpectomy. It predicts the chances for recurrence and the benefit you would receive from getting radiation therapy as part of your treatment. This is a newer use of the Oncotype DX, so NCCN and ASCO do not yet include it in their guidelines.
MammaPrint looks at the activity of 70 genes to predict whether the cancer poses a low or high risk of recurrence at 10 years. It can be used for stage I or II breast cancer, regardless of the cancer’s hormone receptor status. In the U.S., the cancer must be node-negative and no larger than 5 centimeters across.
Seven to 10 days after a sample is sent to a central lab, you will get one of these results:
- Low risk: You have a 10 percent chance the cancer could metastasize within 10 years if you do not get any additional systemic therapies like hormonal therapy or chemotherapy after surgery. Systemic treatments such as chemotherapy or hormonal therapy may further lower your risk.
- High risk: You have a 29 percent chance the cancer could metastasize within 10 years if you have no further treatments after surgery, such as hormonal therapy or chemotherapy. You could lower your risk with treatments tailored to your diagnosis.
Other genomic tests you may hear about include PAM50 (Prosigna) and the Breast Cancer Index.
Though their names sound similar, genomic and genetic tests are two different things. Genetic tests look at your DNA to see if you were born with a genetic mutation, or error, in a specific gene that raised your risk of breast cancer. Genomic tests include any assay used to look at several genes at the same time to assess for mutations in each gene’s DNA or measure their activity. The genomic tests for early-stage breast cancer like Oncotype DX and MammaPrint look at certain genes in the tumor to see how active they are in the tumor cells.
For example, a genetic test could tell you that you have a mutation in the BRCA1 gene, which raises your risk of breast cancer. Based on your genetic test results, you might choose to take preventive actions to minimize your chances of developing breast cancer.
Public and private insurance usually cover the costs of Oncotype and MammaPrint, but check with your health insurance carrier before you get the tests. If they are not covered fully or you do not have insurance, ask your treatment team or social worker for information about financial assistance plans. The test makers also offer patient assistance programs.