Except in Rare Cases, Childhood Cancer Not a Family Affair
Although some forms of cancer tend to run in families, a study of more than 42,000 brothers and sisters of children with cancer in Denmark, Finland, Norway, and Sweden found that only those children whose siblings had rare, inherited cancers were at greater risk for developing cancer themselves, report Jeanette Falck Winther, MD, and colleagues. The study is published in the Sept. 1 issue of The Lancet.
"We compared the risk of siblings of cancer patients to people in general, and we found that they had 24% greater risk of developing cancer themselves," says Winther, a staff member of the Institute of Epidemiology, Danish Cancer Society, in Copenhagen.
"But what we then did was simply take a closer look at the individual [cancer patients] ? and exclude [from the analysis] the very few families in which children suffered from cancers which we were sure had a genetic background," Winther says. "And after that exclusion of only about 56 families, we actually concluded that siblings of cancer patients in general had no greater risk of getting cancer than anyone else."
Scientists have identified more than 450 genetic abnormalities or mutations that may cause cancer, and it is known that the siblings of children with some rare forms of cancer, including the eye tumor retinoblastoma, are at increased risk for developing cancer themselves. There is also a rare disease, known as the Li-Fraumeni syndrome, in which members of an extended family are at greatly increased risk for developing breast cancer, leukemia, brain tumors, and other cancers.
Much less is known, however, about the genetic risks for so-called sporadic or randomly occurring cancers -- until this study.
The study suggests that sporadic cancers do not have a strong a genetic component, which should give some degree of comfort to the families of children with cancer, Winther tells WebMD.