Background: Family history of colorectal cancer among adult patients has been reported in the literature. Although extremely rare in children, colorectal cancer in this population may represent a unique group in whom genetic factors play a significant etiologic role. The aim of the present study was to assess genetic contribution, as measured by family history, to the development of colorectal cancer in probands under 21 years of age at diagnosis.
Procedure: Detailed family histories were obtained from surviving patients or their parents. The risk [standardized incidence ratio (SIR)] of cancer in the relatives was calculated by comparing the observed and the expected incidence based on rates in the general population and person-years at risk.
Results: Twenty-five patients (median age at diagnosis 15 years) diagnosed with colorectal cancer at St. Jude Children's Research Center since 1964 or their surviving next of kin were available for interview. The 461 relatives contributed 18,908 person-years of follow-up. Statistically significant increased risk of colorectal cancer was present among all relatives (SIR = 6.0, 95% CI, 2.7-10.6), and the increased risk of colorectal cancer was confined to relatives of probands who were under 15 years of age at diagnosis (SIR = 10.0, 95% CI, 4.5-17.6). In addition, there was an excess of uterine/cervical cancer among all female relatives (SIR = 6.5, 95% CI, 3.2-10.9).
Conclusions: The observed excess of colorectal cancer, in relatives of younger probands, suggests the need to examine these kindreds for genetic instability resulting from defects in mismatch repair genes to characterize further the patterns of risk observed.
Copyright 1999 Wiley-Liss, Inc.