What are the epidemiological data of childhood malignancies in the u.s. and are any preventable at all?

Can't prevent:: Leukemias and cancers of the brain and central nervous system account for more than half of childhood cancers.The causes of childhood cancers are largely unknown. Each year in the U.S. There are approx.12, 400 children between the ages of birth and 19 years of age who are diagnosed with cancer. About one in 300 boys and one in 333 girls will develop cancer before their 20th birthday.