Familial risk of tumors associated with hereditary non-polyposis colorectal cancer: a Swedish population-based study

BACKGROUND: Familial clustering, which may be due to inherited predisposition, is seen in several common cancer types. The aim of this study was to assess the familial risk of tumors that are associated with hereditary non-polyposis colorectal cancer (HNPCC), a familial cancer syndrome that confers an increased risk of several cancer types, and is associated with a low age at onset. METHODS: The National Swedish Cancer Registry and population registers were utilized to identify all tumors among the offspring of individuals who had developed any of the diagnoses included in the Amsterdam II criteria for HNPCC. In all, 204,358 offspring of 102,814 individuals with cancer of the colorectum, endometrium, upper urinary tract or small intestine were identified. RESULTS: Significantly increased risks for several tumor types were demonstrated. If the parent was below age 50 at diagnosis, the offspring Standard Incidence Ratios (SIRs) were 3.6 for colon cancer, 3.8 for rectal cancer, 2.8 for gastric cancer, and 2.3 for ovarian cancer. Offspring who had both a parent and a sibling with HNPCC-associated cancer showed even higher SIRs for cancer of the colorectum, endometrium, ovary, and urinary tract. The highest values were observed in the subgroup whose parent had developed multiple primary tumors; SIR 34.0 for colon cancer, 17.9 for rectal cancer, 21.8 for endometrial cancer, and 5.8 for ovarian cancer. CONCLUSIONS: The study demonstrates that there is an increased risk for several tumor types among individuals whose parents developed HNPCC-associated tumors, where a young age at diagnosis and development of multiple tumors in the parents lead to the highest SIRs.