Importance of Testing of Cancers With NTRK Gene Fusions

Module 2

Testing for NTRK gene fusions allows for the identification of patients who may benefit from TRK inhibitor therapy. Information on NTRK gene fusions testing is reviewed over the following pages, and the recommended NTRK gene fusions testing algorithm can be found here.

Techniques used to detect NTRK gene fusions include DNA-based next-generation sequencing (NGS), RNA-based NGS, reverse-transcriptase PCR (RT-PCR), fluorescence in situ hybridisation (FISH), and immunohistochemistry (IHC). Each technique detects the NTRK gene fusions either at the DNA, RNA, or protein level (see below).

Table 18: Techniques to Detect NTRK Gene Fusions

Technique Use
NGS Detects known and novel fusions with breakpoints in DNA or RNA
RT-PCR Detects known fusion transcripts in RNA
FISH Detects gene rearrangements in DNA that may generate a fusion transcript
IHC Useful in detecting TRK proteina

aIHC can detect the TRK protein expression only.
FISH, fluorescence in situ hybridisation; IHC, immunohistochemistry.