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Clinical challenges in management of familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer

Received May 25, 1999; accepted June 3, 1999. As of 1999, it is possible to test selected subjects for carriage of germline mutations in genes responsible for familial adenomatous polyposis (FAP), hereditary nonpolyposis colorectal cancer (HNPCC), Peutz-Jeghers syndrome, and juvenile polyposis. These diseases are heterogeneous phenotypically, but there are principles involved in the approach to genetic testing and management that are common to all. Because recognition of the Peutz-Jeghers syndrome and juvenile polyposis genes is so recent and the conditions are so rare, it is premature to speculate about the impact of genetic testing on their management. Genetic testing in FAP has had an extraordinary impact, mainly by virtue of the ability of a negative genetic test to exclude a group of otherwise at-risk children from the necessity of intensive surveillance. However, because the phenotype of FAP is, in most cases, straightforward, with the typical polyposis antedating cancer by a period of years, surveillance and management may be carried out reasonably well even in the absence of genetic testing. Attention will be devoted primarily to the issues involved in recognizing subjects for whom it is appropriate to consider mutational testing for the presence of mismatch repair (MMR) gene mutations in HNPCC. This will be followed by a brief description of such testing. The discussion concludes with an overview of the approach to counseling about positive and negative test results, as well as measures for surveillance and surgical and medical (chemoprevention) management.