Substances present in the environment may trigger certain rare kinds of childhood cancer, according to a new study1 by Cancer Research UK scientists in Manchester.
Professor Jillian Birch and her team found clusters of cases that appeared close together over a short period of time. This pattern suggests that something present in the environment at certain times – such as traffic pollution, pesticides or infections, could be responsible.
Scientists believe studying the patterns of childhood cancer will help identify the causes of the disease and may prevent cases in the future.
Earlier this year Prof Birch and her colleagues from Cancer Research UK’s Paediatric and Familial Cancer Group at the University of Manchester found the first evidence that childhood brain cancer could be caused by infection with bacteria or a virus.
In this study they analysed around 1390 cases of childhood cancers other than brain, diagnosed between 1954 and 1998, from the North of England. Using statistical techniques they looked at whether there were more cases than expected in any one area over a short period of time – a pattern known as space-time clustering.
Clustering is typical of diseases caused by exposure to a fluctuating factor present in the environment for limited periods of time.
The researchers found clusters of cases for two types of cancer, Wilms tumour and soft tissue sarcomas (see notes below for details), when they looked at the time and place of birth of the children.
Prof Birch says: “Our study is the first to demonstrate space-time clustering for Wilms tumour and soft tissue sarcomas.
“Children with these cancers shared the same environment at birth and probably before birth, so it’s possible that something in the environment during this time contributed to their cancer.”
Researchers found that for both types of cancer the risk was higher for males and for Wilms tumour there was a greater risk for older children.
Prof Birch explains: “We believe that most cases of childhood cancer are caused by a combination of genetic and environmental factors.
“When children’s cancers are inherited they usually appear at an earlier age. The fact that clusters of Wilms tumour cases appeared in older children suggests something in the environment is triggering the disease – probably during pregnancy. And genetic differences between the sexes may make males more susceptible to this environmental trigger.”
The researchers also found that children born in less populated areas were at greater risk of Wilms tumour while those born in densely populated areas had a higher risk of soft tissue sarcomas.
Professor Birch says: “Information about population density gives us clues to the type of environmental agent that could be responsible for the cancers.
“In less populated areas, such as rural areas, something like a pesticide which has a very local application may be responsible. While in densely populated areas, such as cities, an outbreak of infection may be more likely.”
Professor Robert Souhami, Director of Clinical Research, at Cancer Research UK says: “This study allows us to build a better picture of the complex causes of childhood cancer. The results are very interesting, but we now need further studies to confirm that environmental factors are involved in these cancers. We can then attempt to identify the agents responsible and use the information to prevent cases in the future.”
- International Journal of Cancer103 (2)
Wilms tumour is a cancer of the kidney which is usually diagnosed in children aged between one and five years old. The disease affects around 70 children each year in Britain.
Soft tissue sarcomas are cancers that develop in the supporting tissues in the body apart from the bones.
Around 85 children are diagnosed in Britain each year with soft tissue sarcomas.
The survival rate for Wilms tumour is around 80% and 67% for rhabdomyosarcoma, the most common soft tissue sarcoma in children.