Hereditary colorectal cancer: clinical consequences of predictive molecular testing.

The continuing increase in knowledge about the genetic basis of carcinogenesis has led to diverse efforts to exploit this knowledge clinically, primarily in the form of predictive genetic testing. In conjunction with family history, gene tests are intended to improve individual cancer risk assessment. The objectives of predictive molecular testing are to identify the disease-causing germline mutation in an index person who has already developed the disease and to distinguish asymptomatic mutation carriers from non-mutation carriers within a given cancer-prone family. At present, genetic testing for colorectal cancer risk, primarily in form of DNA sequencing, is applied in familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC). In these inherited colorectal tumor syndromes determining the genetic status may result in an individually tailored surveillance program and prophylactic treatment. The implications of genetic testing for the clinical management of disease, both of mutation and non-mutation carriers, in familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer families are discussed.