Oncology news - lowering risk for leukemia

A new analysis of published studies has found that children who attended day care or playgroups had about a 30% lower risk of developing acute lymphoblastic leukemia (ALL) than children who did not.

ALL is the most common type of childhood leukemia, accounting for more than 80% of cases, and typically occurs in infants between the ages of 2 and 5 years. It is one of the most common cancers in children in the industrialized world, affecting about 1 in 2000 children.

One theory about how the disease develops focuses on early infection. Some proponents of this theory believe that if the immune system is not challenged early in life and does not develop normally, then it mounts an inappropriate response to infections encountered later in childhood, the charity explains. This could provoke the development of leukemia in children who are susceptible, for example, because of a genetic mutation.

Children who attend day care and playgroups are likely to be exposed to common infections early in life; such environments are known to increase the spreading of infection. The latest finding supports the theory that early exposure to infection offers some protection against the disease.

The analysis included 14 published studies and involved 6108 children with and 13,704 without leukemia. Parents were asked about day care and playgroup attendance and other forms of social interaction. Twelve of the studies showed that social interaction had a protective effect against leukemia and 2 showed no effect. Overall, the risk for leukemia was lowered by about 30%. This remained the case when the researchers re-analysed the data and considered only children who had attended day care before the age of 2 years. When 5 studies were excluded because of concerns about the methodology that had been used, analysis of the remaining 9 studies found that the risk for leukemia was lowered by 40%.

Source: 2nd Children with Leukaemia Causes and Prevention of Childhood Leukemia Conference. Presented April 29, 2008.