Simple steps such as allowing children to attend a day nursery so they come into contact with germ-laden youngsters, breastfeeding, outdoor play and not overly cleaning the house could all help boost immunity, the study suggests.
Professor Mel Greaves, Director of the Centre for Evolution and Cancer at The Institute of Cancer Research, London, said: "The research strongly suggests that ALL has a clear biological cause, and is triggered by a variety of infections in predisposed children whose immune systems have not been properly primed.
"The most important implication is that most cases of childhood leukaemia are likely to be preventable.
"It might be done in the same way that is currently under consideration for autoimmune disease or allergies – perhaps with simple and safe interventions to expose infants to a variety of common and harmless bugs."
The new research is the most comprehensive analysis ever carried out into the illness, which is the most common type of childhood cancer, affecting more than 600 children each year in Britain.
Acute lymphoblastic leukaemia is particularly prevalent in affluent societies and is increasing in incidence at around 1 per cent per year.
The study found that ALL is partially caused by a genetic mutation which predisposes some youngsters to the disease. But only 1 per cent of children born with this genetic change go on to develop cancer.
Prof Greaves concluded that the disease is triggered later in childhood when youngsters are exposed to common infections, particularly youngsters who experienced 'clean' childhoods in the first year of life, without much interaction with other children.
He suggests that it might be preventable if a child's immune system is properly 'primed' in the first year of life – potentially sparing children the trauma and life-long consequences of chemotherapy.
The study also rules out possible environmental causes, such as ionising radiation, electricity cables, electromagnetic waves or man-made chemicals.
Dr Alasdair Rankin, Director of Research at the blood cancer charity Bloodwise, which has funded Professor Greaves' work for over 30 years, said: "Decades of research by Professor Greaves have shown that the most common type of childhood leukaemia is most probably caused by an abnormal response to infection in children already at risk.
"Current treatments for childhood leukaemia are not always successful, and even when they are, can have severe short and long-term side effects, so research to find kinder treatments is very important.
"If we could stop this type of leukaemia from happening in the first place it would be enormously exciting, but many more questions still need to be answered in the research lab before we will know for sure whether that could become a reality."
Professor Paul Workman, Chief Executive of The Institute of Cancer Research, London, added: "It's exciting to think that, in future, childhood leukaemia could become a preventable disease as a result of this work.
"Preventing childhood leukaemia would have a huge impact on the lives of children and their families in the UK and across the globe."
The research was published in the journal Nature Reviews Cancer.
This article originally appeared on the Daily Telegraph and is reproduced with permission.
