Family history of hematopoietic and other cancers in children with acute lymphoblastic leukemia.

It has been difficult to show a genetic contribution for many cancers, resulting in the belief that rare cancers such as leukemia are sporadic. We carried out a population-based case-control study including 701 incident cases of acute lymphoblastic leukemia (ALL) aged 0-14 years and diagnosed between 1980 and 1998 in Québec (Canada); 701 healthy controls were matched on age and sex. Cancer family history in the child's relatives was reported by parents. A positive family history of hematopoietic malignancies among first- or second-degree relatives was associated with a slight increase of risk for childhood ALL (odds ratio 2.06; 95% confidence interval=1.22-3.49); the excess was attributable to second-degree relatives, and observed for grandparents as well as for uncles/aunts. The risk of ALL was not increased in children with a family history of cancers other than hematopoietic cancers. The data suggest a modest familial contribution to childhood ALL.