Childhood Cancer

Cancers occurring in childhood and adolescence differ markedly from adult cancers in terms of the magnitude of the burden and biologic characteristics. Worldwide, the average annual incidence among children aged less than 15 years is 150 cases per million people and among adolescents aged 15-19 years the average annual incidence is 200 per million people. Incidence rates vary by geographical location, with the highest rates found in North America, Oceania, and Europe (Figure 19.1).

While young children (ages 0-14) often develop leukemia and embryonal tumors, adolescents (ages 15-19) are more frequently diagnosed with lymphomas, carcinomas, or germ cell tumors (Figure 19.2).

Overall, cancer is about 20% more frequent in boys than in girls, although some types occur more often in girls (Figure 19.3). The steady increase in incidence rates over time remains mostly unexplained, but has been partly related to improved diagnosis over time. Exposures to high doses of ionizing radiation, high birth weight, and certain genetic syndromes have been consistently associated with increased rates of childhood cancer. The role of other risk factors, such as air pollutants, tobacco or pesticide use, older parental age, or fewer children per family is being investigated.

Mortality is disproportionally higher in low-income countries despite lower incidence rates (Figure 19.1), largely due to poorer survival. Only 30% of children diagnosed with leukemia in Kenya survive for three years, compared to approximately 90% in Puerto Rico and Costa Rica. (Figure 19.4). Factors contributing to these inequalities include lack of awareness, delayed or incorrect diagnosis, and barriers to treatment such as unaffordability, abandonment, or unavailability.