Childhood brain cancer may be caused by infection
Cancer Research UK scientists have found the first tentative evidence that children's brain cancers could be caused by infection with bacteria or a virus.
And researchers noticed that children born in winter had a higher risk of some types of brain cancer than those born in spring or summer, also suggesting that a fluctuating environmental factor, such as an infection, might be responsible for the disease.
Childhood brain cancer is a rare disease, affecting around 290 children in the UK each year and causing about 100 deaths. Scientists from Cancer Research UK's Paediatric and Familial Cancer Group at the University of Manchester analysed 1045 cases of the disease, all from the North West of England, dating from 1954 to 1998. They used sophisticated statistical techniques to explore the pattern of incidence, to try to determine possible causes.
Researchers found that in certain years more children were diagnosed with cancer who lived close together than would be expected by chance, a pattern known as space-time clustering. This produces short-lived mini-epidemics at various times in different parts of the region.
Space-time clustering is a pattern typical of diseases that are caused by infections. In contrast, diseases caused by more constant environmental factors will produce clusters of cases in one place over a much longer time period.
Team leader Prof Jillian Birch comments: "Our results indicate that environmental factors are involved in causing brain tumours in children and the most likely explanation for the pattern we have seen is that one or more types of infections are responsible."
Clustering of cancer cases was especially clear for two particular types of brain tumour - called astrocytoma and ependymoma. Children's risk of these cancers also varied depending on the time of year they were born, with those born in late autumn or winter at the highest risk. This may be because children are more prone to infection during the cold winter months.
Prof Birch adds: "The fact that the space-time clusters and the seasonal pattern in births are restricted to particular types of childhood brain tumours adds weight to our findings and will allow us to focus our future research on these cases."
Last year, Prof Birch and her colleagues found that the rate of children's brain cancer has been increasing gradually since the 1950s. They had suspected that environmental factors such as infections might be responsible for the increase and carried out the current study to look for evidence for their theory. Scientists now believe that further research is needed to confirm that infections are involved and try to identify the agents.
Prof Gordon McVie, Joint Director General of Cancer Research UK, says: "It's vital that we learn more about the causes of childhood cancers and this is an important step in the right direction.
"We'd thought infection might play a role in the development of children's brain cancer, but up until now we had no evidence to support the theory."
Sir Paul Nurse, Joint Director General of Cancer Research UK, says: "We believe that infections play a role in a number of cancers, so it's interesting that a virus or bacterium may also be implicated in the development of brain tumours in young people. These initial findings aren't conclusive and we need more evidence to support them, but if an infection is playing a role, this might lead to new ideas for preventing and treating this important disease."
Scientists believe that around one sixth of all cancers are caused by viruses, the best known being cervical cancer, which is linked to infection by human papillomavirus (HPV). A bacterial infection has been strongly implicated in the development of stomach cancer.