No excess of early onset cancer in family members of Wilms tumor patients

BACKGROUND, Wilms tumor is one of the few pediatric cancers with well-defin ed familial and genetic components. The authors assessed the risk of early- onset cancers in first- and second-degree relatives of patients enrolled by the National Wilms Tumor Study Group. METHODS. Using a stratified sampling scheme that targeted 530 families of p atients who were believed a priori to have a genetic contribution to their disease, the authors conducted interviews regarding cancer occurrence in 42 58 family members from 296 families of patients with Wilms tumor. Reports o f malignant neoplasms that occurred before 55 years of age were confirmed b y review of medical records wherever possible. A period of risk was defined for each family member based on calendar time and his or her relationship to the proband. RESULTS. Ninety-nine cancers were observed, whereas 126.8 were expected by applying standard cancer rates for age and calendar period to the 120,885 p erson-years at risk. The standardized incidence ratio (SIR) was O-E = 0.78 with 95% confidence interval (CI) of (0.64, 0.95). In subgroup analyses, th e highest relative risks were observed for parents of the index case (O/E = 21/13.0 = 1.6, 95% CI = 1.0, 2.5) and for leukemia (O/E = 9/4.9 = 1.9, 95% CI= 0.85,3.5). CONCLUSIONS. The results of this study may provide reassurance to families of children who have had Wilms tumor. Potential sources of bias included th e low (56%) rate of participation of targeted families. In general, the bia ses might have led to the underreporting of some cancers, especially in mor e distant relatives. The possibility of a slight excess of cancer in parent s of Wilms tumor patients could not be excluded. (C) 2001 American Cancer S ociety.