The Canadian Childhood Cancer Surveillance and Control Program (CCCSCP) Facts and Figures Cancer is relatively uncommon in children. In 2002, of nearly 8 million Canadian children and adolescents younger than 20 years of age, an estimated 1,300 were diagnosed with cancer. Nevertheless, cancer is the most common disease-related cause of death, second only to intentional and unintentional injuries as the leading cause of death in this age group, excluding the first year of life. In 2002, there were approximately 250 childhood deaths attributed to cancer.

Cancer in children and adolescents differs from those occurring in adults. Most cancers in adults are carcinomas (ie. Cancers arising in glands or tissues that line organs such as the breast, lung, prostate or colon), but these cancers are very rare in younger age groups. Cancer in children is more diverse, and includes a much higher proportion that are of hematopoietic (blood and lymphatic) origin.

In contrast to adult cancers, primary prevention is limited due to insufficient knowledge regarding modifiable risk factors. Furthermore, no effective screening method is currently available. As a result, improvements in health depend upon advancements in the areas of treatment and management of complications. Fortunately, treatment has improved dramatically, representing one of modern medicines greatest success stories.

Three-year survival rates for childhood cancer now exceed 80 percent. Five-year rates are now more than 70 percent. While efforts to further increase the survival rate for all children with cancer continue, quality of life for patients following successful treatment has received increased attention. The significant improvement in survival necessitates a need to better monitor and develop awareness regarding the long-term health risks associated with the disease and its treatments. Such endeavours are now feasible as larger cohorts of children survive into adulthood. However, little is known about the long term outlook for cancer survivors with respect to their lifelong adjustments.

Incidence rates are highest in the first five years of life:

• 25 cases per 100,000 per year for infants (younger than one year)
• 21 cases per 100,000 per year for children ages one to four
• 12 cases per 100,000 per year for children ages five to nine
• 11 cases per 100,000 per year for children ages ten to fourteen
• 19 cases per 100,000 per year for adolescents ages fifteen to nineteen

Most common cancers

Among infants, the most common cancers are neuroblastomas (22 percent) followed by leukemias (17 percent), central nervous system tumours (13 percent) and retinoblastoma (11 percent).

The most common cancers for children between the ages of one and four are leukemias (43 percent), central nervous system tumours (16 percent), followed by neuroblastoma and Wilms' tumour (both 9 percent).

Lymphomas are the third most common cancer (12 percent) in the five to nine year age group after leukemias (32 percent) and central nervous system tumours (30 percent).

In the 10 to 14 year age group, cancers of the central nervous system are the most common (25 percent), followed by leukemia (23 percent) and lymphomas (20 percent).

In the 15 to 19 year age group, the most common cancers were lymphomas (29 percent), carcinomas (19 percent), followed by germ cell tumours (15 percent) and leukaemia (11 percent).

A higher number of boys than girls are diagnosed with most cancer types. However, girls outnumbered boys in the categories of carcinomas, renal tumours and other and unspecified malignant neoplasms.

What we know about causes

• Genetic predisposition appears to play a significant role in childhood cancer.
• Strong evidence of a causal relationship to leukemia has been demonstrated for prenatal exposure to ionizing radiation.
• Epstein-Barr virus is etiologically linked to Burkitt's lymphoma.