Cancer isn’t one disease. Each person's cancer has its own genetic signature that makes it unique. Your doctor can analyze your cancer's genes to predict how it will behave, how quickly it will grow, and which treatments are most likely to work against it.
Genomic testing is a way to learn more about your cancer. These tests find gene changes, or mutations, in your cancer that help it grow. Genomic testing can sometimes be a useful tool for planning your cancer treatment.
Genomic tests may not be for everyone. For example, if you have a slow-growing cancer that's easy to cure with a certain type of treatment, you may not need more advanced genomic testing. Often, genomic tests are used for rare cancers or for cancers that haven't responded to treatment.
Your doctor will tell you about your genomic testing options and whether these tests are a good fit for you. There are a few reasons why your doctor might recommend genomic testing.
Match a Treatment to You
Treating cancer used to be one-size-fits-all. Everyone with the same type of cancer would get the same treatment, such as chemotherapy or radiation. Today, more than 50 targeted therapies are FDA-approved to treat cancer, and many more are in clinical trials. Targeted treatments, also called precision medicine, work against the specific gene changes that help your cancer grow.
The most common reason that cancer doctors do genomic testing is to find the right treatment. For example, some people with chronic myeloid leukemia (CML) have a change to a gene called BCR-ABL that makes their body produce the tyrosine kinase protein. This protein helps their cancer grow. Tyrosine kinase inhibitors work against CML that has the BCR-ABL gene change.
Another example is epidermal growth factor receptor (EGFR) inhibitors, which treat lung cancers with EGFR gene changes. And PARP inhibitors treat ovarian cancers that have mutations to the BRCA genes.
Genomic testing also helps predict how quickly your cancer is likely to grow. Whether your cancer is slow-growing or aggressive is another way for your doctor to find the right treatment for you.
See if Your Cancer Is Resistant to Treatment
Sometimes, genomic tests can show whether a treatment won't work for you, or if it might stop working. About 20% of people with acute myeloid leukemia (AML) have a mutation in the isocitrate dehydrogenase (IDH) gene. They're treated with medicines called IDH inhibitors.
But people with certain gene changes eventually become resistant to IDH inhibitors. The medication stops working in them. Genomic tests can help doctors predict which people could become resistant, so they can start on a different treatment.
Find Out if You Need More Treatment
Genomic tests can also be useful after your cancer treatment. Your doctor might suggest these tests if the medication you took didn't slow your cancer, or if your cancer came back after treatment.
These tests can also help your doctor determine whether your cancer is likely to come back after surgery. If it's likely to return, you may need more treatment.
Reduce Your Risk for Side Effects
Cancer treatments like chemotherapy and radiation kill healthy cells along with cancer cells. Because targeted treatments based on your genes are more precise, they can help prevent damage to your healthy cells and reduce your risk for side effects.
Find a Clinical Trial for You
Another use for genomic tests is to help your doctor match you to a clinical trial of a new cancer drug. Basket trials are a type of study researchers use to find out whether a certain treatment works on people who share the same gene mutation.
Your genes could help match you to an experimental treatment that might work better against your cancer than treatments you've already tried, or that are available for your cancer. The treatment that is most effective against your cancer might be approved for a different type of cancer than the one you have.
American Cancer Society: "Cancer Patients May Not Be Told About Costs of Genomic Testing," "How genes can help in the diagnosis and treatment of cancer," "Targeted Drug Therapy for Non-Small Cell Lung Cancer."
American Society of Clinical Oncology Education Book: "Integrating Genetic and Genomic Testing Into Oncology Practice."
Biomarker Research: "Isocitrate dehydrogenase inhibitors in acute myeloid leukemia."
BreastCancer.org: "Tumor Genomic Assays."
Cleveland Clinic: "How Genetic Testing Can Make Your Cancer Treatment More Effective."
Dana-Farber Cancer Institute: "What is Genomic Testing?"
Dignity Health: "Fighting Cancer With Genomics in Arizona."
Medscape: "Genomic Testing and Precision Medicine in Cancer Care."
National Cancer Institute: "Basket trial," "Biomarker Testing for Cancer Treatment," "Targeted Cancer Therapies."
The Jackson Laboratory: "Questions to Ask About Genomic Tumor Testing."
Washington University School of Medicine: "Personalized medicine: How genetic research is transforming cancer care."
Zero Cancer: "Genomic & Genetic Testing."