EP85 – Somatic genetic alterations in the RET and RAS genes are associated with worse clinical characteristics of sporadic medullary thyroid carcinoma

      Vaclavikova, Eliska1; Dvorakova, Sarka1; Sykorova, Vlasta1; Vcelak, Josef1; Vlcek, Petr2; Bendlova, Bela1 1 Dept. of Molecular Endocrinology, Institute of Endocrinology, Prague, Czech Republic 2 Dept. of Nuclear Medicine and Endocrinology, 2nd Faculty of Medicine in Charles University and University Hospital Motol, Prague, Czech Republic   Background: Activating somatic mutations in the RET proto-oncogene cause the sporadic medullary thyroid carcinoma (MTC). Also RAS mutations have been discovered in genetically analyzed tumor tissues. Our investigation has been focused on detection of somatic mutations in the RET, H-RAS, K-RAS and N-RAS genes in Czech patients with sporadic MTC and influence of the mutations on clinical manifestation of disease. Methods: DNAs of 128 patients with sporadic MTC were isolated from 64 fresh frozen and 64 paraffin embedded formalin-fixed tissue samples. The analysis of RET mutations was performed using Sanger direct sequencing. Most of samples were verified by amplicon next generation sequencing (NGS). The presence of RAS mutations was also analyzed using by NGS. Results: The somatic RET mutation was detected in 57 patients (44.5%), mainly Met918Thr (28,1%). The RAS mutation was only revealed in RET-negative patients (32% of RET-negative patients). In comparison of cohorts with and without somatic mutation, there were significant differences (p<0.05) in evaluation of postoperative calcitonin levels, TNM classification (tumor size, local and distant metastases) and recurrence/disease-free status.  Discussion & Conclusion: The analysis confirmed that the prevalence of RET mutations in Czech patients is comparable with other countries. The presence of somatic mutation is associated with worse clinical characteristics of the disease. Comparing techniques of NGS and Sanger sequencing, NGS improves the detection of somatic mutations as it is able to reveal a mutation in a sample with a small proportion of tumor cells. Supported by the grant projects AZV 16-32665A and MH CZ DRO 00023761.


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