The RET (rearranged during transfection) gene is present in each of the cells in our body. RET is involved in several different processes of cell growth.

If you test positive for the RET alteration, it means that your RET gene is likely driving the growth of your colorectal cancer tumor.

When the RET gene works correctly, it prevents cancer cells from growing. However, sometimes a gene is altered or changed and does not work the way it should. This is called a mutation or alteration. If the RET gene has a mutation, it means that it can actually drive the growth of cancer cells instead of normal cells.

Mutations are either inherited at conception (a germline mutation) or acquired during a person’s lifetime (a somaticmutation). RET mutation changes are acquired.

RET is a frequently altered gene in colorectal cancer, occurring in about three percent of patients.

Typically, a sample of the tumor is taken during a biopsy or surgery and is then sent to a laboratory for biomarker testing. Biomarker testing should be done on the primary tumor (where the cancer began) and any metastatic tumors that occur.

Very few colorectal cancers have changes in one of the RET genes, which can cause abnormal cell growth and lead to cancer. Selpercatinib (Retevmo) is a drug that targets the RET protein. This drug may be used to treat colorectal cancer that is:

• metastatic
• cannot be removed with surgery
• has not improved or has worsened with other treatment

Every treatment has the potential to cause some side effects. Some people may be more sensitive than others to a particular drug. The response to a specific treatment also depends on your other treatments (for example, radiation) and medications. Contact your doctor immediately if you are experiencing severe symptoms.

Possible side effects of these drugs can include high blood pressure, fatigue, decreased white blood cell count, decreased calcium levels, changes in liver function tests, increased cholesterol, changes in kidney function, and abnormal heart function.