• hereditary non-polyposis colorectal cancer
• non-carrier
• colonoscopy

• FAP, familial adenomatous polyposis
• HNPCC, hereditary non-polyposis colorectal cancer

Hereditary non-polyposis colorectal cancer (HNPCC or Lynch syndrome) is an autosomal dominant predisposition for early onset colorectal cancer and other tumours. The mean age at diagnosis of colorectal cancer is about 44 years.¹ At least five genes have been associated with errors in DNA mismatch repair, the genetic basis of HNPCC. A large proportion of HNPCC families (50%–60%) harbour changes in one of two genes, hMSH2 and hMLH1.² Genetic testing for HNPCC has been possible since 1993/4.³ In HNPCC, two important goals of genetic testing are (1) to identify those with a high risk (mutation positive) to promote preventive strategies and reduce morbidity and mortality; and (2) to reduce unnecessary worry among those with a low risk of cancer (mutation negative).⁴ In mutation positive families, predictive testing can determine who is a carrier of a known mutation in the family, and who is not. Carriers of an HNPCC mutation are estimated to have a lifetime risk of developing colorectal cancer of about 80%.⁵ These carriers are advised to adhere to a lifelong screening programme for early detection of colorectal polyps. The screening programme currently includes a colonoscopy every one to two years,^1,6,7 and should be initiated when the patient is between the ages of 20 and 25.¹ Regular screening reduces substantially the morbidity and mortality from colorectal cancer.⁸ Those found not to be carriers of the mutation that runs in their family, “HNPCC mutation negative family members”, are discharged from this burdensome, lifelong surveillance programme. Their risk and that of their children of developing colorectal cancer reverts to that of the general population (5%). In The Netherlands, there is currently no colorectal surveillance programme for the general population aged 50 years and over, as is the case in some …