Drilon Explains Testing for NTRK Gene Fusions

Alexander Drilon, MD, medical oncologist and chief of the Early Drug Development Service at Memorial Sloan Kettering Cancer Center, discusses what to know when testing for NTRK gene fusions in patients with lung cancer.

According to Drilon, testing to find these types of gene fusions is important, and some of the best ways to do so are with comprehensive next-generation sequencing of the DNA and RNA.

Once these NTRK gene fusions are found, TRK inhibitors can be used. Recently, multiple studies demonstrated the efficacy of larotrectinib (Vitrakvi) in both adult and pediatric patients. Treatment with larotrectinib led to robust and durable responses among patients.

Since they are rare, Drilon highlights the importance for clinicians to learn how to test for NTRK fusions.

TRANSCRIPTION:

0:08 | [In terms of testing, we now know that] there are active agents like larotrectinib, and entrectinib for the treatment of NTRK fusion-positive cancers. Testing to find these fusions is important. With this tumor agnostic approval, there are many ways to do this. In an ideal setting, we found that the optimal way to find these fusions is to do comprehensive next-generation sequencing of not only DNA, but also RNA. The latter maximizes the chance of finding these fusions because introns are very expensive, or there are other factors that lead to a lower likelihood of only finding the fusions on DNA.

0:52 | In our center, we've had a good experience with doing both to increase the number of fusions that we find. However, there are different practice environments. If you look at the guidelines that are out there, there are other tests that could be employed. That includes FISH, for example, but you need to do 3 different ones for the 3 different genes. Immunohistochemistry, which looks for expression as a surrogate for the presence of a fusion but doesn't actually find the fusion, but tests like those can be used to screen for these NTRK fusions, if you're in a practice environment where you may not have insurance, or payer coverage for a more comprehensive testing.