BBC News Online: Health

Siblings not at higher cancer risk

The research should reassure parents about their child's risk

The Scandinavian scientists hope their research will be used to help reassure worried parents.

The researchers looked at the 42,000 siblings of 25,000 children with cancer in Denmark, Finland, Iceland, Norway and Sweden.

Among the sample, 353 sibling cancers were diagnosed compared with 284 expected cases.

But when cancers that are known to be inherited were excluded, they faced no increased risk.

The news has been welcomed by cancer charities.

Author Dr Jeanette Falck Winther, of the Institute of Cancer Epidemiology, Copenhagen said: "Our results should reassure childhood cancer patients and their families and will be helpful for paediatricians and genetic counsellors world-wide."

The study showed that 40% of all the cancers found in people under 20 could be attributed to known genetic factors, but that 60% remained unknown.

The researchers did notice a high number of cases of leukaemia among identical twins, but said this was not apparent in siblings in general.

Good news

Dr Mary Berrington, of the Cancer Research Campaign, said the news would provide welcome reassurance to parents.

"It's good news that the siblings of most children with cancer do not appear to be at increased risk of cancer themselves, either in childhood or as adults.

"The excess cancer risk of siblings of children with cancer was attributed almost entirely to rare, known familial cancer syndromes the authors didn't identify any new patterns of cancer risk."

"This study suggests that, if you take out of the equation all the known inherited cancer predisposing syndromes, siblings of children with cancer are not at an increased risk of getting the disease.

"Previous studies suggested that there are likely to be genes we didn't yet know about that explained why brothers or sisters of childhood cancer patients might be more at risk of cancer themselves."

Dr Lucassen added: "This study suggests there are unlikely to be any undiscovered genes that are significant causes of childhood cancer."

The study is published in The Lancet.