Clinical Utility of Testing

Diagnostic and presymptomatic genetic testing is available for Turcot syndrome. Genetic testing of individuals affected with Turcot syndrome may help clarify their diagnosis. The number of polyps, type of brain cancer, and occurrence of extracolonic cancers aid in directing the choice of genetic testing of the APC gene or the mismatch repair genes. For individuals choosing to proceed with mutation analysis, genetic testing may establish the disease genotype in a family and provide the opportunity for informative presymptomatic testing for other family members. Carriers may be offered intense surveillance of appropriate organs, and noncarriers may feel a relief of anxiety and stress. Microsatellite instability testing may be used from tumor specimens, although not all tumors in individuals with a DNA mismatch repair gene mutation will present with DNA replication errors. The benefits and limitations of genetic testing would be the same as those discussed for FAP and HNPCC.

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