Colorectal Cancer: New Tools for Making Decisions About Treatment
This patient fact sheet explains two tests used in an approach called "personalized medicine."
As your health care team guides you through a colorectal cancer diagnosis, they perform many diagnostic tests to understand your tumor type. Most treatment recommendations are based on this important information, which can include details such as your cancer's stage, grade and location. Recent advances in diagnostic testing for colorectal cancer now allow doctors to predict, in some cases, how a patient's tumor will behave so that they can plan treatment accordingly – an approach called “personalized medicine.” This fact sheet describes two such tests.
What new tests are available?
KRAS Mutation Analysis This test for people with metastatic colorectal cancer checks for a mutation, or change, in a gene called KRAS (pronounced K-razz). KRAS is found to be mutated in about 40% of people with colorectal cancer. People who do not have the mutated gene are said to have the “wild type” KRAS gene.
Oncotype DX Colon Cancer Assay This test is for people with stage II colon cancer. It analyzes 12 different genes to give patients a “recurrence score.” The score (a number between zero and 100) estimates the chance of the cancer returning after surgery. A low score means you have a low risk of recurrence, and a high score means your risk of recurrence is high.
What do these tests determine?
KRAS testing determines whether or not your cancer is likely to respond to EGFR inhibitors. Research shows that people who have the KRAS mutation do not respond to drugs called EGFR inhibitors, such as cetuximab (Erbitux) and panitumumab (Vectibix). This means that if you have a “wild type” KRAS gene, EGFR inhibitors may be an option for you. If you have the KRAS mutation, your doctor should recommend treatments other than these for your metastatic colorectal cancer.
Oncotype DX can help your doctor decide if chemotherapy may be right for you. Usually, doctors decide whether or not to recommend chemotherapy after surgery based on general tumor characteristics such as stage, grade and location. This new test gives doctors additional information for making this decision. It can help identify which stage II colon cancer patients are at high risk of recurrence and may thus be appropriate candidates for chemotherapy. Patients at low risk may be able to avoid chemotherapy and its side effects.