121P Spectrum of druggable gene fusions in microsatellite-unstable colorectal tumors

Colorectal carcinomas (CRCs) with high-level microsatellite instability (MSI-H) often contain gene fusions, which involve receptor tyrosine kinases. This study included 105 MSI-H CRCs. NTRK1/2/3, ALK, ROS1 and RET fusions were analyzed by PCR test for 5’/3’-end unbalanced expression, is capable of detecting all translocation variants. The type rearrangements was subsequently determined variant-specific common and, wherever necessary, targeted RNA next-generation sequencing (NGS). NTRK1/2/3 translocations the most common, being detected in 8/105 (8%) CRCs (TPM3-NTRK1 (T8;N10): n = 2; ETV6-NTRK2 (E5;N15): ETV6-NTRK3 4). There 2 tumors (CCDC6-RET (C1;R12) NCOA4-RET (N9del501;R12), respectively) 1 instance SPTBN1-ALK (S7;A20) chimera. 76/105 (72%) negative KRAS, NRAS or BRAF mutations; 10 (13%) these tumors. 29/105 (28%) carried activating lesions RAS/RAF oncogenes; one had both (E5;N15) V600E substitution. Microsatellite-unstable have high frequency druggable rearrangements, deserving particular attention.