The case for surveillance of high-risk' families.

Patients who have an elevated colorectal cancer risk on the basis of heritable susceptibility can be identified in two ways. First, family history information may indicate empirical risks approaching 50%, while assignment of relative risks of 2.0-4.0 to groups of patients fulfilling certain family history criteria is commonplace. Second, assessment of blood samples by mutation analysis of DNA mismatch repair genes that are known to be responsible for hereditary nonpolyposis colorectal cancer (HNPCC) now affords diagnostic assessment in increasing numbers of families. This review explores the issues involved in identifying families with genetic susceptibility to colorectal cancer and discusses the rationale for clinical screening in at-risk relatives.