Basic concepts for genetic testing in common hereditary colorectal cancer syndromes

Abstract

Approximately 5% of colorectal cancers are associated with an autosomal dominantly inherited colon cancer syndrome. The two most common familial colon cancer syndromes are hereditary nonpolyposis colorectal cancer (HNPCC), also called Lynch syndrome, and familial adenomatous polyposis (FAP). In many families with these syndromes, the causative mutation can be identified by genetic testing of an affected individual. If an affected individual tests positive for a disease-causing mutation, unaffected, at-risk family members can have genetic testing to determine whether they have inherited the cancer susceptibility mutation, and a personalized cancer surveillance strategy can be adopted. Genetic testing greatly enhances cancer risk assessment in these families; however, the complicated nature of interpretation of the results of gene testing and the emotional impact of the result require that testing be carried out in conjunction with patient education and informed consent by a provider who has a good appreciation for the challenges. This article describes the genetic testing strategy in HNPCC and FAP.