Common childhood cancers similar in boys and girls (Mar. 2013) Leukemia and cancers of the central nervous system are the most common cancer types diagnosed in children of both sexes aged 0–14 years, accounting for roughly 50% of all cancers in this age group. The distribution of the most common types of childhood cancers is generally the same for boys and girls, except lymphomas are more common in boys, while thyroid cancer, melanoma and other epithelial cancers, grouped together, are more common in girls. Although childhood cancers are rare in Ontario, they place a significant burden on the lives of those affected and their families. Unlike the very different distribution of cancer types in men and women, the most common childhood cancers are generally similar for each sex. Between 2005 and 2009, leukemia and central nervous system cancers accounted for roughly half of all cancers diagnosed in boys and in girls, followed by lymphomas, neuroblastoma (a cancer of the nerve tissues outside of the brain) and soft tissue sarcomas. While the proportion of cancers that were neuroblastoma and soft tissue sarcomas was roughly the same in both sexes, lymphomas accounted for a larger proportion of cancers in boys (13.1%) compared to girls (8.4%), with Hodgkin lymphomas being slightly more common than non-Hodgkin lymphoma in boys and in girls. A grouping of thyroid, melanoma and other epithelial cancers also showed sex differences, with a higher proportion occurring in girls (6.7%) than boys (3.2%); of these, thyroid cancers affected more girls and melanoma affected more boys. The causes of childhood cancers are poorly understood, but family and genetic factors play a role in at least some. For example, children with certain genetic syndromes, such as Bloom syndrome and Down syndrome, are more likely to develop certain cancers, in particular leukemias and lymphomas.2 Genetic factors also play a role in the development of Wilms tumour (a type of renal tumour) and retinoblastoma—two cancers that occur almost exclusively during childhood.2 Although researchers suspect that environmental exposures before birth or during early life may lead to childhood cancer, high levels of ionizing radiation (e.g., from X-rays) is the only environmental exposure with any conclusive link to cancer in this age group, particularly to leukemia. Despite its rarity, childhood cancer places a significant burden on the lives of those it affects. In Ontario, less than 1% (N=1,825) of all new cancers occurred in children (0–14 years old) between 2005 and 2009. Families dealing with this disease face stresses that range from emotional to financial as they navigate through the healthcare and social services available.3 Although more and more children with cancer in Ontario are surviving their illness—largely due to better treatments4—survivors can face poorer overall health as a result of their cancer treatments, including a higher risk of getting new cancers and other chronic conditions as they age.5,6 For more information, see: Pediatric Oncology Group of Ontario at www.pogo.ca. Cancers of children and adolescents and young adults differ from adult cancers (Nov. 2008 Ontario Cancer Fact) at http://www.cancercare.on.ca/cms/one.aspx?pageId=34981. References Steliarova-Foucher E, Stiller C, Lacour B, Kaatsch P. International classification of childhood cancer, third edition. Cancer 2005;103:1457–67. See also http://www.seer.cancer.gov/iccc/iccc3.html. Cancer Care Ontario. Cancer Risk Factors in Ontario: Evidence Summary. Toronto, Canada, 2013. Available from www.cancercare.on.ca/riskfactor. Limburg H, Shaw AK, McBride ML. Impact of childhood cancer on parental employment and sources of income: a Canadian pilot study. Pediatr Blood Cancer 2008;51(1):93–8. Cancer Care Ontario. Cancer in Ontario: Overview, a statistical report. Toronto, Canada, 2010. Available from www.cancercare.on.ca/reports. Oeffinger KC, Mertens AC, Sklar CA, Kawashima T, Hudson MM, Meadows AT, et al. Chronic health conditions in adult survivors of childhood cancer. New Engl J Med 2006;355(15):1571–82. Meadows AT, Friedman DL, Neglia JP, Mertens AC, Donaldson SS, Stoball M, et al. Second neoplasms in survivors of childhood cancer: findings from the Childhood Cancer Survivor Study cohort. J Clin Oncol 2009;27(13):2356–62. Citation: Cancer Care Ontario. Cancer Fact: Common childhood cancers similar in boys and girls. March 2013. Available at http://www.cancercare.on.ca/cancerfacts. Prepared by staff in Prevention and Cancer Control.