Tiered universal screening systems that save lives are cost‐effective
About 15–20% of colorectal cancers exhibit microsatellite instability (MSI) caused by deficient DNA mismatch repair (MMR).1 Most of these cancers (80%) are sporadic, associated with hypermethylation of the MLH1 gene promoter. Lynch syndrome is caused by germline mutations affecting one of the MMR genes (MLH1, MSH2, MSH6, PMS2), and accounts for 15–20% of MMR‐deficient (dMMR) colorectal cancers, or 2–5% of all colorectal cancers, making it the most common hereditary colorectal cancer predisposition syndrome.2 People with Lynch syndrome are at increased risk of several cancer types, especially colorectal cancer: the risk by age 70 years is 10–82%, depending on the mutant gene, considerably higher than that of the general population (4.5%).3
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