http://bmj.com/cgi/content/full/324/7342/870/d
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Susan Mayor London
An epidemiological study carried out in the north west of England has shown for the first time that some types of childhood brain tumours may be associated with viral infection.
The study analysed 1045 cases of brain tumour in children, all from the Manchester Children's Tumour Registry and dating from 1954 to 1998. Results showed that more children who lived nearer to each other than would be expected by chance were diagnosed with two types of brain cancer—astrocytoma and ependymoma—than would have been expected by chance.
This pattern—known as "space-time clustering"—resulted in short lived mini-epidemics at various times. There was marked cross clustering between cases of astrocytoma and ependymoma, suggesting shared aetiological factors.
Analyses of seasonal variation showed that more cases were found in children born in the late autumn or in winter. This may be because children are more prone to catch infections at these times.
No evidence of space-time clustering existed for other groups of brain tumours analysed in the study (British Journal of Cancer 2002;86:1070).
Professor Jillian Birch, Cancer Research UK professorial fellow at the University of Manchester and a member of the brain tumour research group, explained: "There has been much speculation about the role of certain viruses in human brain tumours, but few epidemiological studies have previously addressed the possibility of an infectious aetiology.
"In our study, the pattern of space-time clustering and seasonal patterns for astrocytoma and ependymoma were consistent with an environmental agent—such as a virus or bacterium—being associated with the aetiology of these conditions."
She added: "The results were very highly significant for these two types of brain tumours, revealing a pattern not previously uncovered in childhood brain cancers."
Previous animal work has suggested that viruses can directly transform DNA in certain brain cells that later become cancerous. This contrasts with the indirect mechanism linking viral infection to some cases of leukaemia, in which the virus acts by immune modulation.
"From our results, it seems as if certain brain cell types are more vulnerable to whatever the causative virus is doing—resulting in astrocytoma and ependymoma," Professor Birch suggested.
She added: "It is particularly interesting that both of these types of tumour are slow growing. We found no hint of clusters in more aggressive types of brain tumours."
On the strength of their results, the group now hopes to design a study to investigate the possible association between infection and childhood brain tumours in more depth.
"Eventually, there may be implications for prevention, but this is a long way
down the line. However, the fact that these cancers seems to be caused by viral
infections is good news, because there is the chance that we can do something in
the future to stop them," she concluded.
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Collections under
which this article appears:Other
Epidemiology Cancer:other
Other
Pediatrics |
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