Genetic testing in hereditary non-polyposis colorectal cancer families with a MSH2, MLH1, or MSH6 mutation

About 5% of colorectal cancers are associated with the autosomal dominantly inherited cancer susceptibility syndrome hereditary non-polyposis colorectal cancer (HNPCC).1,2 HNPCC is characterised by a high risk of developing colorectal cancer and endometrial cancer at a young age (cumulative lifetime risk 80-90% and 30-40%, respectively), and by an increased risk of developing various other tumour types, such as ovarian, uroepithelial, small intestine, biliary tract, stomach, brain, and skin cancers.2–5 Germline mutations in one of three mismatch repair genes ( MSH2 , MLH1 , and MSH6 ) were found to be responsible for a majority of HNPCC families.6–9 Knowledge of the causative mutation in a particular HNPCC family enables the identification of at risk family members by genetic testing. Clearly, the absence or presence of a mutation is of considerable medical and psychological significance. Subjects not carrying the mutation are relieved from a continuous anxiety and can be dismissed from medical surveillance, saving them trouble and reducing health care costs.10 Importantly, subjects with the mutation can benefit from a medical surveillance programme. For HNPCC, colonoscopy has been shown to be a potent tool for the detection and treatment of premalignant adenomas or early colorectal carcinomas in at risk subjects, reducing the risk of developing colorectal cancer and decreasing the overall mortality by about 65%.11,12 The possibility of early detection of colorectal cancer by stool analysis using the genetic markers TP53, BAT26, and K-RAS raises expectations for the development of less invasive surveillance procedures.13 Furthermore, intervention trials with non-steroidal anti-inflammatory drugs (NSAID) in subjects at risk for developing colorectal cancer are in progress.14,15 So far, studies on the use of genetic testing in HNPCC families have used families or subjects who had been registered for research purposes.10,16,17 It is …