Detection of <i>NTRK</i> Fusions: Merits and Limitations of Current Diagnostic Platforms.

Abstract

Oncogenic fusions involving <i>NTRK1, NTRK2</i>, and <i>NTRK3</i> with various partners are diagnostic of infantile fibrosarcoma and secretory carcinoma yet also occur in lower frequencies across many types of malignancies. Recently, targeted small molecular inhibitor therapy has been shown to induce a durable response in a high percentage of patients with <i>NTRK</i> fusion-positive cancers, which has made the detection of <i>NTRK</i> fusions critical. Several techniques for <i>NTRK</i> fusion diagnosis exist, including pan-Trk IHC, FISH, reverse transcription PCR, DNA-based next-generation sequencing (NGS), and RNA-based NGS. Each of these assays has unique features, advantages, and limitations, and familiarity with these assays is critical to appropriately screen for <i>NTRK</i> fusions. Here, we review the details of each existing methodology.