Screening of colorectal cancer (CRC) patients for lynch syndrome (LS) emphasizes the need for public insurance coverage of genetic testing: Results of a national program by the Hellenic Society of Medical Oncology (HeSMO).

Abstract

e13141 Background: Lynch Syndrome is associated with germline mutations in Mismatch Repair (MMR) genes ( MLH1, MSH2, MSH6, PMS2). CRC patients whose tumors exhibit high-level microsatellite instability (MSI-H) have an increased probability of LS. Although the diagnosis of LS has important implications for the patient and the family, germline genetic testing is not reimbursed by the Hellenic Public State Healthcare Services. To address this need HeSMO conducted a national program to screen and diagnose CRC patients with LS. Methods: All patients with CRC were eligible. Assessment for LS involved initially screening tumor tissue for the presence of MMR deficiency, either via molecular MSI testing or via immunohistochemistry (IHC) to detect the absence of one or more MMR proteins. Patients with an MMR-deficient tumor in the absence of a somatic cause (e.g. BRAF mutation or MLH1 promoter hypermethylation) underwent genetic counseling and germline testing to confirm a LS diagnosis. Results: From June 2017 to December 2018, 104 patients diagnosed with CRC were enrolled and tested. Median age of diagnosis was 58,5 years (range 32 - 89) and male-to-female ratio was 1.6:1. Fifty patients (48%) had tumors that exhibited the MSI-H phenotype. From the MSI-H tumors, 41 (82%) did not harbor the BRAF V600E mutation and 33 of them (80.5%) did not harbor an MLH1 promoter hypermethylation. Therefore, 33 patients were invited for genetic counseling and testing. Fifteen patients (45.45%) were diagnosed with LS: 6 ( 40 %) had a mutation in MLH1 (one of which had also a mutation in PMS2 gene), 4 (26.6%) in MSH6, 4 (26.6%) in MSH2 and 1 (6.6%) in PMS2. Conclusions: In our series, 30% of the CRC patients with MSI-H tumors were tested positive for LS. These results confirm the value of a universal screening program of CRC patients for LS. Hopefully, these results will convince the Hellenic Public State Healthcare Services to reimburse screening and germline genetic testing of CRC patients for LS.