Critical issues in the identification and management of patients with hereditary non-polyposis colorectal cancer

Abstract

Inherited defects of the DNA mismatch repair system are the underlying cause of the hereditary non-polyposis colorectal cancer (HNPCC) syndrome and are responsible for 3-4% of all cases of colorectal cancer. The HNPCC syndrome also carries the risk of development of additional malignancies such as endometrial, stomach, small bowel, ovarian, pancreas, ureter, renal pelvis, biliary tract and brain tumours. Amsterdam I and II criteria have been developed to clinically identify affected families. The revised Bethesda criteria function to select patients whose tumours should be investigated for microsatellite instability, the molecular hallmark of defects of the DNA mismatch repair proteins such as hMLH1 and hMSH2. Microsatellite instability-positive cases should be investigated for germline defects in the respective genes. This facilitates identification of affected family members that have to be included in special surveillance programmes, while unaffected family members are spared the physical discomfort and psychological burden of cancer surveillance. In this article, strategies for effective clinical as well as genetic detection of affected individuals, surveillance and appropriate preventive measures are discussed. Open questions include the role of chemoprevention, preventive surgical procedures, new endoscopic procedures as well as non-invasive 'virtual colonoscopy' and the exact implications of some mutations of the DNA mismatch repair genes. Perhaps most importantly, efforts should be made to more efficiently transfer information about the HNPCC syndrome and the cancer risk associated with it from the specialists to primary health care providers and the general public.