Familial and
genetic factors are identified in 5-15% of childhood cancer cases. In <5-10% of cases, there are known environmental exposures and exogenous factors, such as prenatal exposure to
tobacco,
X-rays, or certain medications.
[9]For the remaining 75-90% of cases, however, the individual causes remain unknown.
[9] In most cases, as in
carcinogenesis in general, the cancers are assumed to involve multiple
risk factors and variables.
[10]Approximately 1.69 million new cases of invasive cancers are diagnosed annually in the United States. Cancer is the second leading cause of death in the United States among children age 1 to 14 years and there are an estimated 10,270 cases annually in this age group. [
1] The heterogeneity of pediatric cancer is substantial, and even the most common pediatric cancer (ie,
acute lymphoblastic leukemia [ALL]) is characterized by biological and clinical diversity. As a result of this heterogeneity and low incidence, the ability of epidemiologists to ascribe causes to specific childhood cancers is extremely limited.