CANCER IS AN IMPORTANT CAUSE OF MORTALITY
According to the American Cancer Society, childhood cancer is diagnosed in approximately 1 in 285 children by 20 years of age, with an estimated 15,780 cases newly diagnosed in 2014. After the first year of life, cancer is the single most common disease-related cause of death in children. In 2013 in the United States, there were 9408 deaths in children ages 1 to 14 years; of these, 5571 were due to disease and 22% of these (1221) were due to cancer (Fig. 440-1).
CHILDHOOD CANCER IS A NUMBER OF DIFFERENT DISEASES
In children, the spectrum of cancer types differs from that of adults. Reflecting this difference, pediatric malignancies are categorized in the International Classification of Childhood Cancer by histology rather than by site as in adults. Whereas the vast majority of cancer in adults is epithelial in origin (ie, carcinomas), in children most cancers derive from the reticuloendothelium (ie, leukemia and lymphomas), brain and spine, mesenchyme (ie, sarcomas), and relatively undifferentiated tissues (ie, embryonal tumors). The distribution of childhood tumor types in Europe, North America, Africa, and Asia from 2008 is shown in Figure 440-2.
Percentage distribution of tumor types among children 0 to 19 years of age in Europe/North America, Africa, and Asia. (Reproduced with permission from GLOBOCAN: http://globocan.iarc.fr.)
THE INCIDENCE VARIES BETWEEN POPULATIONS
The types of cancers that predominate over the course of childhood change with age. In infants, the most common form of cancer is neuroblastoma (20%), whereas for 1- to 14-year-olds the most common is leukemia (43% of cases, ages 1–4; 35% of cases, ages 5–9; and 25% of cases, ages 10–14). Moreover, some childhood cancers, such as osteosarcoma, have a very distinct peak incidence in adolescence. Figure 440-3 shows the age-incidence curves for childhood cancer overall as well as for 4 individual tumors.
A: Incidence of combined childhood cancers by age, United States SEER program, 2000–2013. B: Incidence of selected childhood cancers by age, United States SEER program, 2000–2013. (Reproduced with permission from Surveillance, Epidemiology, and End Results program: www.seer.cancer.gov.)
Overall, the rate of cancer is about 20% higher in boys than in girls, with the difference being most marked for lymphomas, which are twice as common in boys (...