NTRK genes (called NTRK1, NTRK2, and NTRK3) help make proteins known as TRK proteins (TRKA, TRKB, and TRKC). These proteins usually sit on the surface of nerve cells and help them work properly. The body carefully controls how much of these proteins are made.

Sometimes, though, an NTRK gene can get joined with another unrelated gene—like ETV6, LMNA, or TPM3. This is called a gene fusion. When this happens, the result is a new, abnormal protein called a TRK fusion protein. Unlike normal TRK proteins, this fusion version can appear where it shouldn’t and behave out of control, causing cells to grow and divide too much. This can lead to cancer.

In colorectal cancer (CRC), the presence of this gene fusion is used as a biomarker, which means it can help doctors understand the cancer and guide treatment decisions.

Doctors usually use a method called next-generation sequencing (NGS) to test for NTRK fusions. This test looks closely at your genes and can also identify which other gene is involved in the fusion.

Your results may say:

If a fusion is found, your report might list which NTRK gene and which other gene are involved. For example, it might say “ETV6-NTRK1 fusion detected.”

Keep in mind:

If your tumor has an NTRK fusion, it produces an abnormal TRK fusion protein. Some targeted therapies, called TRK inhibitors, can block this protein and slow down or stop the cancer from growing.

If you do not have an NTRK fusion, there are still many treatment options, including:

• Quimioterapia
• Targeted therapy
• Inmunoterapia

Other biomarker test results can help your doctor decide which treatments may work best for you.

If you have metastatic CRC with an NTRK fusion, there are two FDA-approved drugs you might be able to use:

Larotrectinib

Entrectinib

These medicines block the TRK fusion protein, helping to slow or stop the cancer. The best treatment depends on your unique situation, so talk with your doctor about what’s right for you.