MLH1 promoter hypermethylation in the analytical algorithm of Lynch syndrome: a cost-effectiveness study

Abstract

The analytical algorithm of Lynch syndrome (LS) is increasingly complex. BRAF V600E mutation and MLH1 promoter hypermethylation have been proposed as a screening tool for the identification of LS. The aim of this study was to assess the clinical usefulness and cost-effectiveness of both somatic alterations to improve the yield of the diagnostic algorithm of LS. A total of 122 colorectal tumors from individuals with family history of colorectal cancer that showed microsatellite instability and/or loss of mismatch repair (MMR) protein expression were studied. MMR germline mutations were detected in 57 cases (40 MLH1, 15 MSH2 and 2 MSH6). BRAF V600E mutation was assessed by single-nucleotide primer extension. MLH1 promoter hypermethylation was assessed by methylation-specific multiplex ligation-dependent probe amplification in a subset of 71 cases with loss of MLH1 protein. A decision model was developed to estimate the incremental costs of alternative case-finding methods for detecting MLH1 mutation carriers. One-way sensitivity analysis was performed to assess robustness of estimations. Sensitivity of the absence of BRAF mutations for depiction of LS patients was 96% (23/24) and specificity was 28% (13/47). Specificity of MLH1 promoter hypermethylation for depiction of sporadic tumors was 66% (31/47) and sensitivity of 96% (23/24). The cost per additional mutation detected when using hypermethylation analysis was lower when compared with BRAF study and germinal MLH1 mutation study. Somatic hypermethylation of MLH1 is an accurate and cost-effective pre-screening method in the selection of patients that are candidates for MLH1 germline analysis when LS is suspected and MLH1 protein expression is absent.

MLH1 methylation screening is effective in identifying epimutation carriers

“…If this was the case, MS-MLPA could be a good methodological approach. The robustness and informativeness already shown for paraffin-embedded tissues 24 has been confirmed when being used in the germline. In any case, confirmation with at least another technique (ie, pyrosequencing) would be mandatory.…”

“…The ICO patients were selected from a series of 56 individuals with MLH1-deficient CRC and no germline mutations identified in MLH1. 24 In all, 29 patients met Bethesda criteria, 1 case met Amsterdam criteria and 4 cases showed other types of CRC familial aggregation. Clinico-pathological information was recorded.…”

“…So far, the detection of somatic MLH1 hypermethylation is often used to exclude patients from further MMR mutation analysis, based on cost effectiveness considerations. 24,37 The patients with somatic MLH1 hypermethylation could now be considered as candidates to screen for constitutional MLH1 epimutations. Based on the clinical presentation of the reported cases 5 and our experience, this screening could be restricted to those diagnosed earlier than 50 years or with multiple tumors the first one before the age of 60.…”

“…24 The PCR products were purified using Illustra GFX DNA and Gel Band Purification kit (GE Healthcare, Buckinghamshire, UK). BRAF V600E mutation detection was performed by SNuPE using the ABI PRISM SNaPshot Multiplex Kit (Applied Biosystems, Foster City, CA, USA) and a specific primer.…”

Select Biomarkers for Tumors of the Gastrointestinal Tract: Present and Future

“…The cascade leads to the activation of cell growth and differentiation. The V600E mutation promotes tumor cell viability, proliferation, and growth, 13 and occurs in approximately 10% of colorectal cancers 14 and up to 70% of MSI-H tumors with loss of MLH1. 7 Germline Testing for MMR Mutation.-Once the MMR-deficient gene is identified in the tumor by IHC, the specific mutation can often be identified in DNA from peripheral blood mononuclear cells via targeted gene sequencing combined with multiplex ligation-dependent probe amplification.…”