Family history of cancer and the risk of childhood solid tumours: a Norwegian nationwide register-based cohort study

Background: It is not clear if family history of cancer increases risk of cancer in children. Methods: We followed-up a total of 2 610 937 children born between 1960 and 2001 for cancer risk, and their parents and siblings. In this period, 2477 primary childhood solid tumours (except lymphoma) were diagnosed. The data from the Norwegian Family and Life Course Study and from the Norwegian Cancer Register were used. Classification of hereditary cancer syndromes was based on tumour histology, pedigrees and Chompret’s criteria. Results: An association between risk of childhood tumours and first-degree family history of early onset of solid tumours was observed for central nervous system tumours (2.3-fold), neuroblastoma (2.3-fold), retinoblastoma (6.1-fold), hepatic tumours (4.0-fold), and melanomas (8.3-fold). Elevated risk was also seen for osteosarcomas (1.5-fold) when considering first-degree family history of cancer diagnosed at any age. The risk of hepatic tumours, neuroblastomas and melanomas remained elevated even after controlling for probable hereditary cancer syndromes. Conclusions: The increased risk for several childhood solid site cancers among those with first-degree relatives diagnosed with solid cancer suggests that genetic or environmental factors are involved. The fact that these associations remained after controlling for hereditary cancer syndromes indicates other genetic mechanisms might be involved.