Genetic Evaluation of Turkish patients with Colorectal Carcinoma in Terms of Lynch Syndrome by Targeted Next Generation Sequencing

Purpose: Lynch syndrome (LS) is a hereditary cancer disorder characterized by increased lifetime risk for various cancers. Colorectal cancer (CRC) is the most common cancer in LS. Germline testing of mismatch repair (MMR) genes is required for definitive diagnosis of LS. The purposes of this study was to report the results of the mutation analysis of MMR genes using targeted next generation sequencing (NGS) in patients with CRC for providing benefits to the diagnosing and management of LS as the first study from Turkey, to our knowledge. Patients and Methods: A total of 28 patients with CRC were evaluated for LS between 2016 and 2017 years. Sequencing analysis by using NGS was performed in MLH1, MSH2, and MSH6 genes and deletion/duplication analysis by using multiplex ligation-dependent probe amplification (MLPA) method were performed in MLH1, MSH2, MSH6, EPCAM genes in 28 patients. Results: A total of 9 variants were found in 28 patients (4 in MSH2, 4 in MLH1, 1 in MSH6). The diagnosis of LS was confirmed in 9 patients (32%; 9/28). Four variants were assessed as known variants, 5 variants as novel. Conclusion: The patients with CRC should be evaluated in terms of LS because of increased lifetime risk of developing various cancers. If there is an indication for LS after genetic counseling, germline testing for definitive diagnosis of LS should be performed.