The neurotrophic tropomyosin receptor kinase (NTRK) family gene rearrangements have been recently incorporated as predictive biomarkers in a “tumor-agnostic” manner. However, the identification of these patients is extremely challenging because the overall frequency of NTRK fusions is below 1%. Academic groups and professional organizations have released recommendations on the algorithms to detect NTRK fusions. The European Society of Medical Oncology proposal encourages the use of next-generation sequencing (NGS) if available, or alternatively immunohistochemistry (IHC) could be used for screening with NGS confirmation of all positive IHC results. Other academic groups have included histologic and genomic information in the testing algorithm.
To apply some of these triaging strategies for a more efficient identification of NTRK fusions within a single institution, so pathologists can gain practical insight on how to start looking for NTRK fusions.
A multiparametric strategy combining histologic (secretory carcinomas of the breast and salivary gland; papillary thyroid carcinomas; infantile fibrosarcoma) and genomic (driver-negative non–small cell lung carcinomas, microsatellite instability–high colorectal adenocarcinomas, and wild-type gastrointestinal stromal tumors) triaging was put forward.
Samples from 323 tumors were stained with the VENTANA pan-TRK EPR17341 Assay as a screening method. All positive IHC cases were simultaneously studied by 2 NGS tests, Oncomine Comprehensive Assay v3 and FoundationOne CDx. With this approach, the detection rate of NTRK fusions was 20 times higher (5.57%) by only screening 323 patients than the largest cohort in the literature (0.30%) comprising several hundred thousand patients.
Based on our findings, we propose a multiparametric strategy (ie, “supervised tumor-agnostic approach”) when pathologists start searching for NTRK fusions.
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This study was mainly funded by Roche Spain through an agreement with “Fundación de Investigación HM Hospitales,” where this study was carried out. Thermo Fisher Scientific provided an unrestricted grant for the optimization of the next-generation sequencing. Molero is supported by the Tom Crean Expedition.
Hernandez receives honoraria from Roche; research funding was received from Roche and Thermo Fisher Scientific. Conde receives honoraria from Roche; research funding was received from Roche and Thermo Fisher Scientific. Garcia-Toro receives honoraria from Roche. Saiz-Lopez receives honoraria from Roche and Bayer. Rojo receives honoraria and research funding from Roche. Boni receives honoraria from Bayer. Teixido receives honoraria from Roche. Paz-Ares receives honoraria from Roche and Bayer. Lopez-Rios receives honoraria from Roche, Bayer, and Thermo Fisher Scientific, and research funding was received from Roche and Thermo Fisher Scientific. The other authors have no relevant financial interest in the products or companies described in this article.