CANCER IN THE PARENTS OF CHILDREN WITH CANCER

Background. Certain types of cancer in children and young adults have been linked with an increased risk of cancer in close relatives. Howev er, the relation between childhood cancer and familial risk remains to be fully assessed in population-based studies. Methods. We conducted a nationwide study in Denmark of 11,380 parents of children with cance r. The children were identified from records in the Danish Cancer Regi stry; their parents were identified from population registers. The occ urrence and rate of cancer in the parents were determined with use of the Cancer Registry's files and compared with national incidence rates for various categories of tumor. Results. Overall, 1445 cancers were diagnosed in the parents, as compared with 1496 expected from national incidence rates, to yield standardized incidence ratios of 1.0 (95 pe rcent confidence interval, 0.9 to 1.0) for all parents, 1.0 for mother s, and 0.9 for fathers. The lower rate of cancer among fathers reflect ed their lower standardized incidence ratio for lung cancer (0.8; 95 p ercent confidence interval, 0.6 to 0.9), as calculated from 114 observ ations. Conclusions. Genetic determinants are important in several typ es of childhood cancer, but the genetic susceptibility to tumors does not generally extend to the parents of children with cancer, nor do th e patterns of incidence point to the influence of shared environmental factors. Thus, cancer in children should not be viewed as a general m arker for an increased risk of cancer in the patients' parents.