Childhood cancer refers to malignancies diagnosed in individuals generally between birth and 14 years of age, sometimes extending through age 19. Statistically, childhood cancer is rare when compared directly to the frequency of diagnoses observed in the adult population. Understanding this disease involves looking closely at the numbers, the types of cancers that arise in children, their underlying causes, and the progress made in treatment outcomes.
Defining Rarity: Incidence and Statistics
The rarity of childhood cancer is established by comparing its incidence rate to that seen in adults. In the United States, the annual rate of new cancer diagnoses for children under 15 is approximately 17.14 cases per 100,000 children. This rate is low compared to adults aged 40 to 64, who experience about 528.9 diagnoses per 100,000 people per year, or adolescents aged 15 to 39, who have a rate of 74.9 cases per 100,000 annually.
Childhood cancers constitute a small fraction of all cancer diagnoses, representing about 1% of the total new cancer cases each year. Although the incidence rate has shown a slight increase over recent decades, the overall number remains small. Despite its rarity, cancer remains the leading cause of death by disease among children after infancy in the United States.
The Most Common Types of Pediatric Cancer
The cancers that affect children are fundamentally different from those commonly occurring in adults. Adult cancers are predominantly carcinomas, arising from epithelial tissues like the lungs, breast, and colon. Pediatric cancers, in contrast, often originate in the blood, lymphatic system, brain, bone, and nerve tissue.
The most frequently diagnosed group is leukemia, accounting for nearly 30% of all cases in children under 15. These blood cancers, such as acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML), start in the bone marrow. The second most common group is central nervous system (CNS) tumors, including brain and spinal cord tumors, which make up about 20% of childhood malignancies.
Other categories include lymphomas, which arise from immune system cells, and embryonal tumors. Neuroblastoma is the most common cancer in infants, while Wilms tumor is a form of kidney cancer often seen in children aged 2 to 5. These distinct tumor types reflect their origin in rapidly developing tissues.
Why Childhood Cancers Occur
The causes of childhood cancers differ considerably from those driving most adult malignancies. Pediatric cancer is rarely associated with lifestyle choices or years of environmental exposure, unlike adult cancer. The vast majority of childhood cancer cases, estimated at 85% to 90%, are considered sporadic, meaning they arise from random genetic mutations.
These sporadic cancers are primarily caused by somatic mutations—changes in a cell’s DNA that occur after conception, often during periods of rapid cell growth. The rapidly proliferating cells may be more susceptible to errors in DNA replication that lead to uncontrolled growth. Since these mutations are not inherited, they are considered chance events that are not preventable by current known measures.
A smaller portion of childhood cancers, approximately 5% to 10%, is linked to inherited genetic syndromes. These children are born with a germline mutation, a DNA change passed down from a parent or occurring new at conception, which increases their risk. Even with this predisposition, cancer development still requires additional genetic mutations to occur.
Current Survival Rates and Long-Term Outlook
The prognosis for children diagnosed with cancer has improved dramatically due to advances in treatment protocols. The overall five-year survival rate for childhood cancer is now over 85%, a significant increase from the 1970s when the rate was only about 58%.
This high survival rate means a large and growing number of individuals are childhood cancer survivors. For some specific cancers, such as acute lymphoblastic leukemia, the five-year survival rate is now well over 90%. This success shifts the focus toward survivorship, which involves managing potential long-term health issues that may arise years after treatment is completed.