Why it's done

The goal of precision medicine for breast cancer is to tailor treatment to your particular genetic makeup and the genetic changes in the cancer cells.

Precision medicine for breast cancer may involve analyzing the genetic makeup of your cells or, if you have cancer, the makeup of your cancer cells. Tests might include:

• Drug-gene testing. Your genes may influence the way your body processes medications, including those used to treat breast cancer. Your doctor may use information from a genetic test of your cells to determine which medications and dosages are most appropriate for you. The field of drug-gene interactions is called pharmacogenomics.
• Advanced cancer. If your cancer progresses despite treatment, your doctor might recommend testing the genetic makeup of your cancer cells. This test, called tumor sequencing, is used to look for changes or alterations in the cancer so that your doctor can choose the best drug for your type of tumor.
• Family history. Genetic testing for inherited gene mutations that increase your risk of breast cancer, such as the BRCA gene, is offered to people with a strong family history of the disease. Women who have these genes have an increased risk of developing breast cancer compared with the general population. This same test can also be used to determine if you would respond to a specific drug for the treatment of metastatic breast cancer (Parp inhibitor). Other, newer genetic tests may be available, too, depending on a person's family cancer history.