The Diagnostic Value of Pan-Trk Expression to Detect Neurotrophic Tyrosine Receptor Kinase (NTRK) Gene Fusion in CNS Tumours: A Study Using Next-Generation Sequencing Platform

Abstract

Background: Neurotrophic tyrosine receptor kinase (NTRK) fusion has been detected in rare types of CNS tumours, which can promote tumorigenesis. The efficacy of Trk inhibitor became a significant therapeutic interest. Our aim was to investigate whether Pan-Trk immunohistochemistry (IHC) is a reliable and efficient marker for detecting NTRK-fusion in different brain tumours.Methods: This study included 23 patients diagnosed with different types of CNS tumours. Testing for Pan-Trk IHC with monoclonal Ab (EPR17341) has been performed on all FFPE tissues. Parallelly, NTRK-rearrangements were tested using both DNA and RNA-based next-generation sequencing (NGS) assay using TruSight Onco500 platform.Results: The cohort included eight pilocytic astrocytomas, one oligodendroglioma, six IDHwildtype glioblastomas, four IDHmutant grade four astrocytomas, and one sample of each (astroblastoma, central neurocytoma, medulloblastoma, and liponeurocytoma). The mean age was 35 years; seven cases were in the paediatric age group, and 16 were adult. Pan-Trk expression was detected in 11 (47.8%) tumours, and 12 (52.1%) tumours showed no Pan-Trk expression. Nine Cases (82%) with different Pan-Trk expressions did not reveal NTRK-rearrangement. The other two positively expressed cases (liponeurocytoma and glioblastoma) were found to have NTRK2-fusions (SLC O 5A1-NTRK2, AGBL4-NTRK2, BEND5-NTRK2). All the 12 cases (100%) with no Pan-Trk expression have shown no NTRK-fusions. There was no statistically significant association between Pan-Trk expression and NTRK-fusion (p = 0.217). The detection of NTRK- fusions using NGS had high specificity over NTRK-fusion detection by using Pan-Trk IHC.Conclusion: Pan-Trk IHC is not a suitable tissue-efficient biomarker to screen for NTRK-fusions in CNS tumours, however RNA-based NGS sequencing should be used as an alternative method.

Tropomyosin receptor kinase B (TrkB) signalling: targeted therapy in neurogenic tumours

“…Current techniques for detecting TRK fusions mainly include immunohistochemistry [ 45 ], fluorescence in situ hybridisation (FISH) [ 49 ], reverse transcription polymerase chain reaction (RT‐PCR) [ 50 ], and next‐generation sequencing (NGS) using DNA or RNA [ 51 ]. Given the low frequency of TrkB fusion in neuro‐derived tumours, the inclusion of the NTRK gene in RNA‐based NGS analysis is recommended with high specificity [ 51 , 52 ].…”

NTRK-fused central nervous system tumours: clinicopathological and genetic insights and response to TRK inhibitors

“…The use of alternative molecular testing methods such as direct sequencing or in situ hybridization is not recommended because of the diversity of NTRK fusions observed in various central nervous system (CNS) tumours, with NTRK1 /2/3 interacting with multiple fusion partners [ 10 ]. Pan-TRK immunohistochemistry (IHC) using antibodies such as EPR17341 (Ventana, ready to use, Export, US) and A7H6R (Cell Signaling, 1:50, Massachusetts, US) is available but has exhibited inconsistent reliability as a screening tool for NTRK fusions [ 2 , 25 ]. Until pan-TRK IHC is adequately optimized to serve as a surrogate marker for NTRK fusion, NGS remains the most precise method for confirming the diagnosis of NTRK-fused tumours.…”