Background: We performed a retrospective analysis to determine the incidence of neurotrophic tropomyosin-receptor kinase (NTRK) fusion in non-small cell lung cancer (NSCLC). Methods: Archival NSCLC tissues between 2018–2020 were screened by immunohistochemistry (IHC) with IHC-positive cases undergoing confirmatory molecular analysis. Correlative clinicopathologic parameters were collected. Results: Of 289 samples analyzed, 10 (3.5%) cases had NTRK expression on IHC. The median age of patients with NTRK-positivity on IHC was 74.9 (range, 44–88) years and 70% had a smoking history. The cohort included seven adenocarcinomas and one each squamous cell carcinoma, large-cell neuroendocrine and not otherwise specified histologies. PDL1 expression was ≤50% in five cases. Concurrent EGFR mutations were detected in three cases, with two cases also showing a PIK3CA E542K mutation and MET amplification, respectively. Due to insufficient tumor material, RNA-sequencing was undertaken in only one IHC-positive case, with the other nine cases analyzed by Fluorescent in-situ Hybridisation. A NTRK fusion, EML4-NTRK3 gene fusion was detected in one patient, a frequency of 0.35%. Conclusions: NTRK fusions in NSCLC are rare. This study highlights real world diagnostic challenges regarding NTRK testing, such as requirements of adequate tumor tissue and appropriate testing methodologies.
Funding
Bayer (Australia) provided funding to support the analysis for the study (Ref: SM_NTRK_July21).