Each tumor has its own biological makeup, based on the genes found in its cells. The genes in tumor cells are different from genes in healthy cells. An important area of cancer research is understanding this biology. With this information, it’s possible for doctors to know whether a particular tumor is likely to respond to a specific therapy, allowing for the best possible treatment approach. This is known as precision (or personalized) medicine.
To better understand the biological makeup of a person’s tumor, doctors look for changes in genes within the tumor that may serve as “markers.” Markers can predict whether a given treatment will be effective against a tumor and the risk of the tumor recurring (the cancer returning).
Following are tumor markers and genetic changes that can be identified in colorectal cancer.
A key group of tumor markers that have been found in colorectal cancer consists of changes in KRAS and NRAS—known collectively as the RAS genes. Over 40 percent of people with colorectal cancer have a mutation (change) in a RAS gene. Through clinical trials, researchers have learned that these people do not benefit from treatment with the EGFR inhibitors cetuximab and panitumumab (see “Targeted Therapy” section). However, the presence of these genetic alterations does not affect response to chemotherapy.
The other 60 percent of people with colorectal cancer have no RAS mutation. These people are said to have the RAS “wild-type” gene. These individuals have a higher likelihood of benefiting from treatment with EGFR inhibitors.
Approximately 10 percent of people with colorectal cancer have a mutation in the BRAF gene. As with RAS mutations, the majority of these people do not respond to EGFR inhibitors. Clinical trials have shown there are certain drugs that can block this BRAF gene, which may allow patients with this mutation to respond to treatment with EGFR inhibitors. This is an active area of research, and combination therapies that block the BRAF gene are now available.
About 4 percent of metastatic colorectal cancers (cancers that have spread to other parts of the body) have a genetic trait known as high microsatellite instability (MSI-H), which causes these tumors to have a large number of genetic mutations. There are three drugs approved by the U.S. Food and Drug Administration (FDA) for the treatment of this type of tumor (see “Immunotherapy” section). Additional treatment approaches are being studied in clinical trials.
In very rare cases, a genetic abnormality can cause the neurotrophic receptor tyrosine kinase (NRTK) gene in a cancer cell to become connected (fused) to another unrelated gene. When this occurs, it causes uncontrolled “signaling” of tropomyosin receptor kinase (TRK) proteins that can lead to tumor growth.
TRK inhibitors have been approved by the FDA for the treatment of people with colorectal cancer that exhibits this genetic abnormality (see “Targeted Therapy” section).
As you manage your colorectal cancer, it’s important to remember that you are a consumer of health care. The best way to make decisions about health care is to educate yourself about your diagnosis and get to know the members of your health care team, including doctors, nurses, nurse practitioners, physician assistants, dietitians, social workers and patient navigators.
Here are some tips for improving communication with your health care team:
Start a health care journal. Having a health care journal or notebook will allow you to keep all of your health information in one place. You may want to write down the names and contact information of the members of your health care team, as well as any questions for your doctor.
Prepare a list of questions. Before your next medical appointment, write down your questions and concerns. Because your doctor may have limited time, ask your most important questions first and be as specific as possible.
Bring someone with you to your appointments. Even if you have a journal and a prepared list of questions or concerns, it’s always helpful to have support when you go to your appointments. They may also think of questions to ask your doctor or remember details about your symptoms or treatment that you may have forgotten.
Write down your doctor’s answers. Taking notes will help you remember your doctor’s responses, advice and instructions. You can also ask the person who accompanies you to take notes for you, either in your journal or on a tablet or smartphone.
Record your visit if your doctor allows it. Recording the conversation with your doctor gives you a chance to hear specific information again or share it with family members or friends.
Incorporate other health care professionals into your team. Your medical oncologist is an essential member of your health care team, but there are other health care professionals who can help you manage your diagnosis and treatment:
Your primary care physician should be kept updated about your cancer treatment and any test results.
Your local pharmacist is a great source of knowledge about the medications you are taking. Have all of your prescriptions filled at the same pharmacy to avoid the possibility of harmful drug interactions.
Make sure your oncologist knows of any other medical conditions you have or any pain you are experiencing so that they can consult with your primary care physician or specialists as needed.
Remember, there is no such thing as over-communication.