The Grapevine

Leukemia, Most Common Childhood Cancer, May Be Triggered By Too Much Cleanliness

While some parents would aim to raise their child in a clean, germ-free clean environment, an influential scientist from the United Kingdom highlights why too much of a good thing can be bad.

In a new study, a two-step process was revealed to be the most likely cause of childhood leukemia. The landmark paper titled "A causal mechanism for childhood acute lymphoblastic leukemia" was published in Nature Reviews Cancer on May 21.

Leukemia is regarded as the most common form of childhood cancer, accounting for nearly 29 percent of childhood cancer cases. Professor Mel Greaves, from the Institute of Cancer Research in London, assessed the most comprehensive body of evidence ever collected on acute lymphoblastic leukemia (ALL). Often diagnosed in children under the age of 4, the blood cancer can quickly spread and is treated with chemotherapy. 

"I have spent more than 40 years researching childhood leukemia, and over that time there has been huge progress in our understanding of its biology and its treatment," he said, revealing how nearly 90 percent of cases are cured in the modern age. "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."

He studied more than 30 years of research on the genetics, cell biology, immunology, epidemiology and animal modeling of leukemia. In his conclusion, he found a two-step process of genetic mutation to be the cause of the disease.

The first step involves a pre-birth genetic mutation which affects the fetus and predisposes the unborn child to leukemia. However, only 1 percent of those born with this genetic risk may actually develop the disease.

The second step explores those among the 1 percent who will find the disease to be triggered during childhood by a second genetic fault. According to Greaves, this can occur due to exposure to infections, particularly among children who did not interact with other infants or children and experienced a "clean" childhood during the first year of life.

"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," he said. "The research strongly suggests that (this cancer) 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 study also challenged previous findings which suggested ionizing radiation, electricity cables, electromagnetic waves or man-made chemicals to be possible environmental causes of the cancer.

Greaves, as well as other experts, wanted to emphasize that parents should not feel responsible for triggering childhood ALL. "If their child has an accidental mutation in the womb that’s nobody’s fault," Greaves said, adding that he is conducting further research on whether exposure to harmless "bugs" is able to prevent leukemia in mice.