Differences Between Genetic and Genomic Tests

Genetic Tests

According to what we know now, only 5 to 10% of breast cancers in the United States are linked to an inherited gene mutation. Of those, half are linked to abnormal structural changes in the BRCA1 or the BRCA2 gene, both of whose functions are to repair damaged DNA by making proteins that act as tumor suppressors. When a mutation of this type is passed down, it can pave the way for out-of-control cell division leading to a greatly increased risk of breast and/or ovarian cancer.

To be clear, the vast majority of breast cancer patients do not carry any of these transmitted mutations. However, when a patient has a strong family history of breast cancer, and comes from certain susceptible racial or ethnic populations, genetic tests exist that can confirm or rule out this hereditary aspect of the disease. These tests are usually done on a blood or saliva sample and sent to a commercial lab. Though some women decide on their own to be tested prophylactically in order to identify and manage possible future cancer risk, it is imperative to seek counsel from one’s health care provider before making the decision of whether to undergo genetic testing or not.

Genomic Tests

More and more women with a breast cancer diagnosis are advised to have their biopsied tumor tissue analyzed through genomic tests such as Oncotype DX or Mammaprint. In contrast to genetic testing that analyzes a single gene and its role in transmitting certain traits or conditions from parent to child, genomic testing studies all genes and their interrelationships to figure out their combined effect on living beings. When dealing with breast cancer, what is the purpose of these tests and can we be sure that the results are accurate when it comes to making therapeutic decisions? The intrinsic goal of genomic testing is to see if there is a better way to understand a patient’s personal breast cancer physiology (structure) and how it will react to treatment, compared to the traditional pathology report which lumps all similar subtypes together. If we can confidently assess the risk of future recurrence based on a woman’s specific, individual tissue, we can decide if the side effects, toxicity and expense of chemotherapy are worth taking on.

To ensure maximum support and comprehension of what is at issue, consulting your health care provider before deciding to get tested is vitally important. No test is 100% foolproof but with a doctor’s guidance, genomic test results can be a useful tool to help steer treatment choices.