Public health perspectives on testing for colorectal cancer susceptibility genes

About 131,600 new cases of colorectal cancer will be diagnosed in the United States in 1998. About 27,900 men and 28,600 women will die from colorectal cancer in 1998. Mutations to the hMSH2 gene on chromosome 2p and to the hMLH1 gene on chromosome 3p have been identified as causes of colorectal cancer. These mismatch repair genes, which have recently been cloned, account for most cases of hereditary nonpolyposis colorectal cancer (HNPCC), one of the most common cancer susceptibility syndromes known. The carrier frequency of hMSH2 and hMLH1 gene mutations in the U.S. population is unknown. An adenomatous polyposis coli (APC) gene variant (I1307K allele), which was recently reported in 1 in 17 Ashkenazi Jewish persons, may double the risk for colorectal cancer in that population.

The use of genetic tests for susceptibility to cancer of the colon and other sites needs careful scrutiny. Several issues must be addressed before such tests can be recommended for population-based prevention programs. For example, the screening of population subgroups raises concern about potential discrimination and stigmatization. Before genetic tests for colorectal cancer are incorporated into future programs, the safety, effectiveness, and quality of these tests must be evaluated.