Characterization of NTRK gene fusion events in solid tumors among Chinese patients.

Abstract

e15040 Background: NTRK fusions are actionable genomic alterations detected across tumor types. NTRK gene fusions involving either NTRK1, NTRK2 or NTRK3 (encoding the neurotrophin receptors TRKA, TRKB and TRKC, respectively) are oncogenic drivers of various adult and paediatric tumour types. Here, we update the detection of NTRK gene fusions across tumor types and further describe fusion partner characteristics among Chinese patients. Methods: Samples submitted for clinical molecular profiling were retrospectively analyzed for NTRK fusion events. Method for identifying NTRK fusions was DNA-based next-generation sequencing that tumour DNA is extracted from formalin-fixed paraffin-embedded tissue. All NTRK fusion partners were identified for intact functional domains, domain prediction, breakpoints, frame retention and co-occurring alterations. Results: A total of 64 NTRK fusion events (0.26% of 24,451) were identified. NTRK fusions are characteristic in a few rare types of cancer, such as melanoma, glioma and carcinomas of the thyroid, lung and colon, but they are also infrequently seen in some uncommon cancers, such as secretory carcinoma of the breast or salivary gland and infantile fibrosarcoma. Among the fusions, NTRK1 (0.08% of 24,430), NTRK2 (0.02% of 24,445), NTRK3 (0.15% of 24,414) were identified. Twenty-six unique fusion partners were identified, the most common in NTRK1 fusion being TPM3 (23.8%), NTRK2 fusion being AGTPBP1 (33.3%), and NTRK3 fusion being TFG (13.5%). Almost 53.8 % (14 of 26) of all fusion events are expected to include the transmembrane domain contributed by the NTRK fusion partner. The most commonly identified breakpoints occur in exon 14 and exon 17 and in exon 15 and exon 20, in NTRK1, NTRK3, respectively. Conclusions: NTRK fusion products are diverse across tumor types, but the significance of these variations is not clear. The biological and clinical implications of retaining certain domains of NTRK and of fusion partners warrants further investigation.