Precision Medicine in Cancer Care

Not everyone reacts to a medicine in the same way. Health care providers and patients would like to know ahead of time whether a particular treatment is more likely to work for that particular patient. This is where the emerging field of precision medicine comes in. Precision medicine looks at an individual's genes, environment and lifestyle to better predict whether a specific treatment will be more effective.

At MUSC Hollings Cancer Center, we are applying the concepts of precision medicine to cancer care. As a patient, you may be told that your providers are using biomarker testing, molecular testing, genomic testing or other types of tests. These tests are all meant to help doctors to make more informed recommendations about the types of treatment that you should get.

Our mission is to help patients better understand molecular testing in cancer and to provide resources to help everyone to make sense of this complicated topic and to make informed decisions about their health.

Precision oncology at Hollings

Not all cancers are the same - even when they come from the same region of the body. Breast cancer in one woman can be very different than breast cancer in another woman. There are molecular differences between tumors, and providers want to match each tumor to the treatment that will be most effective against it. Although tumors may have mutations, not all mutations are inherited and some of the testing recommended by your provider may help identify which mutations are inherited.

Although all inherited mutations that can increase risk for cancer are rare, some have been highlighted over the years. For example, the BRCA1 gene may increase risk for cancers including breast, ovarian, prostate, pancreatic and other cancers. These mutations may be called “germline” or “constitutional” mutations. Our team assesses all of our patients for the possibility of inherited mutations and the Hollings Hereditary Cancer Clinic helps assure these patients and their families have the information and appropriate monitoring they need.

However, in most tumors, the genetic mutations are only in the tumor and not in the rest of the body’s cells. These mutations are not inherited but considered to be “acquired” during the lifetime of the patient. Tumors are made up of cells that started out as normal cells, then acquire genetic changes that lead to growth that is not under control. So, a cancer will have many mutations that are specific to it and not seen anywhere else in the body. For example, even if you did not inherit BRCA1 from a parent, the tumor cells may have acquired a BRCA1 mutation. There are hundreds of genes that may be mutated in a tumor and identifying the right mutations may lead to “targeted” cancer care with medicine that is more specific for each tumor. These mutations may be called “acquired,” “somatic” or “tumor-associated” mutations.

Whenever possible, our providers use such testing, in consultation with the precision pathology and oncology teams, to help determine which treatments might be most effective for you. Most of this testing happens behind the scenes, after a discussion between you and your health care providers, but your provider will tell you if there is a result that changes the course of action. In some cases, one of our clinical trials may be right for you.

Family cancer syndromes

Some inherited mutations can cause patterns of certain types of cancers that run in families. These are called family cancer syndromes. More information about some of these is below.

What is Li-Fraumeni syndrome?

Li-Fraumeni syndrome (LFS) is an inherited familial characteristic that could lead to certain, often rare, cancers due to mutations in the TP53 tumor suppressor gene. TP53 is a tumor suppressor, and it gives instructions for making proteins that control how fast cells grow and divide to make new cells. TP53 proteins help stop the growth of abnormal cells.

What is Lynch syndrome?

Lynch syndrome is an autosomal dominant trait that is an inherited copy of an altered gene in each cell that causes higher cancer risks. Not all people that inherit the variants in the genes causing Lynch syndrome develop cancer.

Tests used in precision oncology

These are a few of the tests that might be performed after you are diagnosed with cancer.

Germline testing (genetic testing)

Germline testing looks for gene mutations that you inherited from your parents. These mutations have been with you since birth. Even if you're already been diagnosed with cancer, it's important to know whether you have these inherited mutations. They could mean that one treatment is more likely to be successful than another. Also, if you find that you have a hereditary cancer, your siblings and children should get genetic testing to see if they carry these gene mutations that make cancer more likely. Knowing that they have these genetic mutations will empower them to make preventive and monitoring choices before a cancer diagnosis.

Somatic testing (tumor testing, genomic testing, molecular testing, tumor subtyping)

Somatic testing looks for gene mutations inside the cancer tumor. These mutations weren't inherited from your parents; they happened somewhere along the way. Mutations aren't unusual. They can happen when your cells are exposed to certain substances, like radiation or tobacco smoke. Most of the time, though, they simply happen with aging. When your body is copying 330 billion cells each day, mistakes can happen. Your cells have a system in place to catch most of those mistakes and destroy them. But when mutations occur in genes that are responsible for DNA repair or for suppressing tumors, then cancer can begin to grow.

Biomarker testing

Biomarker testing can be germline or somatic. A biomarker is a gene, protein, molecule or other substance in your body; like a flag raised in a race, it alerts doctors that something is happening. We don't yet know the biomarkers for every type of cancer, but scientists are continuing to search for biomarkers that can help doctors and patients to make more precise treatment choices. These are some of the different types of biomarkers:

• Risk biomarkers indicate you have the potential to develop a disease. By knowing this ahead of time, doctors can be prepared. For example, some women who learn they have a BRCA gene mutation decide to have a preventive mastectomy. Others may prefer more frequent mammograms and MRI testing.
• Diagnostic biomarkers show doctors the subtype of cancer that you have.
• Monitoring biomarkers help doctors to follow your progress over time. For example, a man with somewhat elevated prostate specific antigen (PSA) markers may decide on active surveillance rather than immediate treatment for prostate cancer, because prostate cancer is usually slow growing. His doctor will regularly check his PSA levels; if they reach a certain level, then the doctor and patient may decide to proceed with treatment for prostate cancer.
• Predictive biomarkers indicate which patients are more likely to benefit - or to have a negative outcome - from a particular treatment. For example, predictive biomarker testing in non-small cell lung cancer shows doctors which types of chemotherapy will be most helpful for an individual patient.

Common questions about cancer testing

Meet the director

Thai Ho, M.D., Ph.D.

Dr. Ho is the Director of Precision Medicine at MUSC Hollings Cancer Center. He has been caring for patients affected by genitourinary cancers for over 10 years. His area of expertise and the focus of his research is in treating kidney and bladder cancers. He also sees patients with kidney, bladder, upper tract urothelial, and prostate cancers, as well as patients affected by hereditary cancer syndromes.

His research is funded by the National Institutes of Health and Department of Defense to better match cancer patients with targeted therapies by using precision medicine approaches to identify a cancer's unique vulnerabilities.