[Interaction of cancer family history and environmental factors in the risk of cancer--with special reference to childhood malignancies].

Association with family history of cancer of each site was examined for each type of childhood malignancies using data of National Childhood Malignancy Registry in Japan as materials (n = 16,555). 2,926 cases were with cancer family history. Family history of same type of malignancy was found significantly in excess for leukemia, a malignant lymphoma, brain tumor, neuroblastoma and retinoblastoma. When observed by cell type, association with family history of leukemia was most striking in acute myeloid leukemia. Median age at first diagnosis of retinoblastoma was 11 months earlier when family history of retinoblastoma existed. Family history of leukemia and history of exposure to prenatal radiation exposure was found to enhance relative risk for childhood leukemia when combined, suggesting existence of genetic environment interaction. Mode of interaction was interpreted as multiplicative.