Search

The National Registry of Childhood Tumours contains over 51000 records of children born in Great Britain who developed cancer under the age of 15 years. Patterns of childhood cancer among families containing more than one child with cancer have been studied. A total of 225 "sib pair' families have been ascertained from interviews with parents of affected children, from hospital and general practitioner records and from manual and computer searches of names and addresses of patients. A number of special groups have been identified, including those with a known genetic aetiology such as retinoblastoma, twins and families with three or more affected children. A further 148 families not in any of the above groups contain two children with cancer: in 46 families the children had tumours of the same type, most commonly leukaemia. Some of the families are examples of the Li-Fraumeni syndrome; some are associated with other conditions, including Down's syndrome. There is clearly a genetic element in the aetiology of cancer in some families discussed here; shared exposure to environmental causes may account for others and some will be simply due to chance.

It has been suggested in a number of recent reports that there is a possible relationship between parental occupation and malignant disease in children. A proportional mortality analysis relating deaths among children in England and Wales in 1959-63 and 1970-72 to occupation of father as stated on the child's death certificate has not shown any convincing evidence for such associations. Earlier papers published on the subject are reviewed. Although there is some slight evidence for associations between childhood tumours and certain parental occupations there is little consistency between the results reported by different authors. A previously reported association between higher social class and deaths from neoplasms was found also in this study. The explanation for this finding is unknown, and it remains possible that it is an artefact.

A series of 1,438 parents and 2,663 other relatives of retinoblastoma patients have been followed up to ascertain the incidence among them of non-ocular cancer. Among 117 of these relatives who were known carriers of the mutation of the retinoblastoma gene 23 cases of non-ocular cancer developed during the follow-up period of the study. This compares with an expected number of 2.3, a relative risk of 9.9. A total of 25 deaths among these carriers included 21 from non-ocular cancer; the expected number was 1.8, a relative risk of 11.6. Relatives who are carriers are about 15 times more likely to die from lung cancer than the general population. Previous findings of an association of melanoma and bladder cancer with retinoblastoma are borne out in this study. The incidence of non-ocular cancer among relatives of hereditary cases who are not definitely known to be carriers shows an excess risk of 1.6: it is concluded that a proportion of these relatives are in fact carriers of the mutated retinoblastoma gene. For relatives who are not gene carriers there appears to be no excess risk of developing cancer. Carriers relatives who are not themselves affected with retinoblastoma may be inherently less liable than affected carriers to the further genetic changes which lead to the development of both retinoblastoma and subsequent non-ocular cancer.

A study was carried out on 11 169 matched case-control pairs of children aged up to 15 years included in the Oxford Survey of Childhood Cancers to see whether an association exists between cancer in children and drugs given to their mothers during pregnancy. The mothers of children who developed cancer reported about 25% more illnesses during pregnancy than mothers of healthy control children. Two specific illnesses, pulmonary tuberculosis and epilepsy, were investigated. For these there was a higher than average case-control excess of reports and there had been a suggestion that the drugs used in treatment, isoniazid and phenytoin, might be carcinogenic. The results of this investigation provide no real evidence for any association between the drugs taken by the mothers during pregnancy and subsequent cancer in the child.