Abstract

Based on an established but pragmatic definition of cancer family syndrome as the presence of three or more relatives affected by colorectal cancer in a first degree kinship, the contribution of this syndrome to the total cancer burden in Northern Ireland has been studied by investigating all non-polyposis probands under 55 years old at histological diagnosis between 1976 and 1978. Family interviews were possible for 95% (n = 205) of all non-polyposis probands and verification of vital status or medical history was obtained for 98% of 1811 first degree relatives. The prevalence of cancer family syndrome was between 1 and 2%, a figure some fivefold less than that estimated elsewhere. A proximal tumour excess was not characteristic of the ascertained families. These results may have implications for the identification of susceptible people if screening for high risk groups is considered a worthwhile option for reducing colorectal cancer mortality in the United Kingdom.