The cause of childhood leukemia may have been found.
Up to now, that is until a major analysis of a comprehensive body of information on acute lymphoblastic leukemia (ALL), the cause of this most common type of childhood cancer, was unknown.
The review by Professor Mel Greaves from The Institute of Cancer Research, London has done away with previous speculations of possible environmental causes, such as ionizing radiation, electricity cables, electromagnetic waves or man-made chemicals and has instead put forward a two-tier cause of the disease.
Not only that. Professor Greaves suggests that childhood leukemia may be preventable.
Isn’t that something?
In a landmark paper published in Nature Reviews Cancer this week, Professor Greaves revealed his conclusions after reviewing the most comprehensive body of evidence ever collected on ALL.
His research concludes that the disease is caused through a two-step process: first, a genetic mutation that occurs in the womb before birth and second exposure to infection during childhood.
The genetic mutation predisposes young children to leukemia, but only 1 percent of these children later develop the disease. It is this 1 percent that later develops leukemia after having been exposed to a range of common viruses and bacteria.
That’s not all.
Another crucial factor is at play here. It seems that it’s primarily children who grow up in really clean conditions in the first year of life, and didn’t enjoy much interaction with other infants or older children who are susceptible to developing the disease.
According to the Institute of Cancer Research, acute lymphoblastic leukemia is particularly prevalent in advanced, affluent societies and is increasing by about 1 percent per year.
Professor Greaves suggests childhood ALL is a paradox of progress in modern societies — with lack of microbial exposure early in life resulting in immune system malfunction.
He presented strong evidence for a ‘delayed infection' theory for the cause of ALL, in which early infection in young children is beneficial to prepare or prime the immune system, but later infection in the absence of earlier priming can trigger leukemia.
What does this mean for parents and small children? It means it’s good for children, even in their first year of life, to get dirty and to interact with other children. Playing in the sand and getting a cold at kindergarten is not such a bad thing, after all.
The Good News
Professor Greaves suggests that childhood leukemia, in common with type I diabetes, other autoimmune diseases, and allergies, might be preventable if a child's immune system is properly ‘primed' in the first year of life.
Professor Greaves said in a statement that he had spent more than 40 years researching childhood leukemia and admitted that a lot of progress had been made so that today around 90 percent of cases are cured.
“But it has always struck me that something big was missing, a gap in our knowledge—why or how otherwise healthy children develop leukemia and whether this cancer is preventable. This body of research is a culmination of decades of work, and at last, provides a credible explanation for how the major type of childhood leukemia develops.
“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.“
Evidence For The Study’s Conclusions
Review of population studies in people together with animal experiments revealed the following telling factors:
In one unique cluster of ALL cases in Milan, seven children who developed leukemia had been infected with swine flu virus during an outbreak of the disease in the city;
Children who attended nursery school or who had older siblings and were therefore exposed to bacteria on a regular basis had lower rates of leukemia;
Mice engineered to have an active leukemia-initiating gene, developed ALL when moved from an ultra-clean, germ-free environment to one that had common microbes;
Breastfeeding with its immune system boosting function protects against ALL.
All these factors point to the possibility that ALL can be prevented.
Professor Greaves is now investigating whether earlier exposure to harmless ‘bugs' could prevent leukemia in mice — with the possibility that it could be prevented in children through measures to expose them to common but benign microbes.
Professor Greaves points out that while exposure to common infections poses a risk of childhood leukemia, other factors like inherited genetic susceptibility and chance also play a role. Secondly, infection as a cause applies to ALL specifically, not to other rarer types of childhood leukemia.