Crude annual incidence rate of medullary thyroid cancer and RET mutation frequency

Aim To determine the frequency and type of RET mutation in Slovenian medullary thyroid cancer (MTC) patients and estimate the crude annual incidence of MTC in Slovenia. Methods This referral-center retrospective analysis involved 186 MTC patients diagnosed between 1995 and 2015 and their relatives who underwent genetic counseling and testing. The crude incidence rate of MTC was estimated with the joinpoint regression analysis. Genomic DNA was isolated, and exons 10, 11, 13, 14, 15, and 16 of the RET proto-oncogene were amplified with polymerase chain reaction. Point mutations of the RET gene were detected by single-strand conformation analysis and DNA sequencing. Detected mutations were confirmed by restriction enzymes. Results The average crude annual incidence rate of MTC in Slovenia was 0.34/100,000. A germline mutation in the RET proto-oncogene was identified in 25.9% of MTC patients. The most frequently altered codons were codons 634 and 618, followed by codon 790, codon 804, and codon 918. Conclusions Annual incidence increase and nation-specific frequency of RET mutations justify the future use of genetic counseling and testing of MTC patients in Slovenia