Prognostic value and characterization of NTRK1 variation by fluorescence in situ hybridization in esophageal squamous cell carcinoma.

Purpose Rearrangement of the neurotrophic tyrosine kinase receptor (NTRK) 1 gene is a target of tropomyosin receptor kinase A (TRKA) inhibitors, and its targeted drug (larotrectinib) has been approved by the US Food and Drug Administration. We investigated the existence and prognostic importance of NTRK1 variation in esophageal squamous cell carcinoma (ESCC). Methods Fluorescence in situ hybridization of a NTRK1 rearrangement was conducted on 523 ESCC samples through tissue microarrays. Kaplan-Meier curves with log-rank tests were used to evaluate survival. Results We identified 8 (1.5%), 35(6.7%) and 109 (20.8%) cases with a NTRK1 rearrangement using 15%, 10% and 5% as cut-off values, respectively. We observed copy number (CN) variation of NTRK1 in some cases: 79 (15.1%) cases had a gain in NTRK1 CN ≥ 3, and 24 (4.6%) cases had NTRK1 CN ≥ 4. A NTRK1 rearrangement at the above-mentioned thresholds was not related to disease-free survival (DFS, P = 0.45, 0.47, 0.87) and overall survival (OS, P = 0.80, 0.74, 0.57), respectively. Gain in NTRK1 CN was associated with a poor prognosis irrespective of whether NTRK1 CN ≥ 4 (DFS, P = 0.015; OS, P = 0.035) or NTRK1 CN ≥ 3 (DFS, P = 0.039; OS, P = 0.025). Conclusion A NTRK1 rearrangement occurred rarely in ESCC. The increased CN of NTRK1 might be a prognostic indicator for DFS and OS in patients with ESCC.