Inherited predisposition to colon cancer.

Abstract

Colorectal cancer is one of the most common malignancies in the United States. Although both genetic and environmental factors play a role in colorectal tumorigenesis, recent advances in genetics have more clearly defined the impact of inheritance in the multistep process of the disease. Researchers have identified single genes that confer a susceptibility to familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC). Because these genes are inherited in an autosomal dominant fashion, offspring of carriers have a 50% chance of inheriting the gene mutation and its associated risk. The FAP gene, when mutated, initiates the neoplastic process. HNPCC gene mutations disrupt mismatch repair, thus inducing progression of tumor formation. Discovery of these genes has helped our understanding of sporadic colon cancer as well. Genetic testing for the FAP and HNPCC genes is now available, and results of this testing have implications for surveillance and management. In addition, testing raises complex psychosocial and ethical issues. At present, genetic testing is primarily conducted in the research setting, but it will soon be available in the clinical arena. To prepare for the challenges that these new advances will present, nurses must begin now to enhance their knowledge of genetics and its application to oncology.