Results of a population-based study published in this week’s issue of THE LANCET suggest that siblings of children with common, non-inheritable cancer are not at an increased risk of malignant disease.
In some rare inherited disorders such as retinoblastoma and Li-Fraumeni syndrome, relatives of children with cancer are at an increased risk of cancer. Jeanette Falck Winther and colleagues from the Nordic Cancer Societies, and US investigators, assessed relations between childhood cancer and sibling risk, and evaluated the influence of recessive conditions in cancer causation.
Data from around 42 000 siblings of 25 000 children with cancer in Nordic countries (Denmark, Finland, Iceland, Norway, and Sweden) were studied. Children with cancer were identified from records in the five Nordic cancer registries, and their siblings from nationwide population registries. Cancers in siblings were documented through record linkage with cancer registries and compared with national incidence rates. The investigators also assessed cancer incidence in parents to identify familial (inheritable) cancer syndromes.
353 sibling cancers were diagnosed compared with 284 expected cases. Siblings aged younger than ten years were two to three times more likely to have cancer than the general population; this increased risk decreased with age, and approached expected rates after age 30 years. However, when data were analysed without familial cancer cases, siblings of childhood cancer patients were at no increased risk. The investigators did not identify any new patterns of familial cancer that indicated inherited susceptibility, or evidence that recessive conditions might contribute to cancers not explained by specific syndromes. They conclude that apart from rare cancer syndromes, paediatric cancer is not an indicator of increased cancer risk in siblings
Jeanette Falck Winther comments: “Exclusion of only 56 families with well-described familial cancer syndromes from the more than 25 000 families included in the study resulted in observed cancer-risks in siblings equivalent to those expected in the general population. Our results should reassure childhood cancer patients and their families, and will be helpful for paediatricians and genetic counsellors worldwide.” (Quote by e-mail; does not appear in published paper).
Contact: Dr Jeanette Falck Winther, Institute of Cancer Epidemiology,Danish Cancer Society, Strandboulevarden 49,DK 2100 Copenhagen,Denmark;T) +45 3525 7670;F) +45 3525 7734;E) jeanette@cancer.dk
Journal
The Lancet