A Health Surveillance Update on Canadian Children and Youth

Cancer Incidence

Although rare, cancer is the most common potentially fatal illness among Canadian children.

Although rare, cancer is the most common potentially fatal illness in Canadian children. Cancer is a collection of diseases that have in common uncontrollable cell growth and the ability to spread to distant parts of the body. Newly diagnosed, or incident, cases of cancer are registered with provincial and territorial cancer registries. Cancer incidence data are published in Canadian Cancer Statistics.⁽¹⁾ The childhood cancer incidence rate is the number of new cases of cancer in children in a defined population (in this case, Canada) per 100,000 children.

There were 873 cases of cancer reported in Canadian children in 1994.⁽²⁾ This corresponds to a rate of  14.7  per 100,000 children per year. Cancer incidence has remained relatively constant over time.  Figure 1 presents the trend in incidence among Canadian children from 1984 until 1994.

Note: Rates are standardized to the age distribution of the 1991 Canadian population.
Source: Cancer Bureau, LCDC, based on Statistics Canada data⁽²⁾

Cancer in children differs from cancer in adults. For example, epithelial cancers (those that arise in glands or tissues that line organs such the breast, lung or stomach) are very rare in children, but are the most common type of adult cancer. Leukemias are the most frequently diagnosed neoplasms in children, accounting for 30% of the new cases. Brain tumours account for 20%, lymphomas for 10% and neuroblastomas for 8% of new cancer cases. Among children, the incidence of cancer is highest in the first year of life. The type of cancer also varies with the age of children. Figure 2 presents the cancer incidence by age group and cancer type for the period 1985-1994.

Source: Cancer Bureau, LCDC, based on Statistics Canada data⁽²⁾

Canadian incidence rates (1988-1992) are similar to or slightly higher than those of most developed countries, such as the United States, Australia, Sweden and the Netherlands.^(3,4) Rates in most Asian countries are 20-30% lower than in Canada. The variation in international cancer rates reflects differences in case ascertainment as well as genetic susceptibility and environmental exposure to carcinogens.

Over the last 30 years, improvements in diagnostic techniques, access to medical care and improvements in cancer registration practices have been reflected in a modest increase in childhood cancer incidence rates internationally. It is uncertain whether there is a genuine increase in risk due to changes in exposure to unknown environmental factors.

Data limitations
There has been an improvement in the quality of childhood cancer surveillance over time. Significant under-reporting of cancer cases is known to have occurred before 1982; details are available in The making of the Canadian Cancer Registry.⁽⁵⁾ Also, national data are currently available only up to 1994.

Summary
The causes of childhood cancer are for the most part unknown. Although childhood cancer is rare, the cancer registries now collect good quality data that will allow continual surveillance of trends and the identification of geographic variation in the diagnosis of childhood cancer by age and type.

Unless referenced otherwise, childhood cancer incidence statistics are the product of the Cancer Bureau, LCDC⁽²⁾

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