Performances of the Idylla GeneFusion Assay: contribution to a rapid diagnosis of targetable gene fusions in tumour samples

Aims We aimed to evaluate the performances of the Idylla GeneFusion Assay (IGFA) designed to detect, in a single, rapid and fully automated assay, ALK , ROS1 , RET , NTRK1 , NTRK2 and NTRK3 gene fusions and MET exon 14 skipping in cancer samples. Methods Based on a set of tumours enriched in cases with gene fusions, we applied the IGFA to tumour areas of various sizes and tumour cell contents. IGFA results were compared with those obtained with other methods (immunohistochemistry, fluorescent in situ hybridisation, DNA and RNA next-generation sequencing). Results We selected 68 tumours: 49 cases with known gene fusions (8 ALK , 8 ROS1 , 5 RET , 7 NTRK1 , 3 NTRK2 and 6 NTRK3 ones) or MET exon 14 skipping mutations (12 cases) and 19 cases with no fusion and no MET mutation. We performed 128 IGFA tests on distinct tissue areas. The global sensitivity and specificity of the IGFA were, respectively, 62.82% and 99.2% with variations between molecular targets and tissue areas. Of note, 72.5% sensitivity and 98.79% specificity were obtained in 37 tissue areas fulfilling the manufacturer’s recommendations (ie, at least 10% of tumour cells in at least 20 mm² of tissue area). The rate of non-conclusive results was higher in small samples with low percentages of tumour cells. Conclusions The IGFA could contribute to the rapid detection of targetable gene fusions and mutations, especially in context of rapidly growing cancers requiring urgent therapeutic choices.