Childhood Cancer

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The New Jersey Department of Health collects health-related data and uses it to do surveillance and research. This report is one of a series including data from the inception of the New Jersey State Cancer Registry through the most recent year complete data were available at the time of publication. The most recently released report, a report of breast cancer in New Jersey, was published in September, 1998.

Serious diseases in children are of great concern to families, the community, and the Department of Health. Even though cancers among children represent only about one percent of all cancers, its patterns in the population merit special attention.

This report presents rates and trends in childhood cancer from 1979 through 1995 for New Jersey and compares them to the nation. Overall, New Jersey mirrors the United States regarding the distribution and trends of occurrence and mortality from childhood cancer. During this 17 year period, incidence rates for most cancers which occur in childhood have increased slightly while mortality rates for every type of childhood cancer have decreased steadily. Researchers have speculated that various factors may be responsible for the increased number of reported cases, including improvements in access to medical care, more complete case ascertainment by registries, new or more extensive environmental exposures, secondary cancers caused by the treatment of the initial cancer, or random variation.

The term "cancer" represents many different diseases, each with a particular distribution pattern in the population by such demographic factors as age, sex and race, and each with its own pattern of risk factors, both known and unknown. For the most common childhood cancers, incidence rates are higher for males than for females and higher for whites than for blacks. Nationally and in New Jersey, leukemias are the most common childhood cancer, accounting for thirty-one percent. Central nervous system cancers are the second most common in the United States and account for about twenty percent. The third most common childhood cancers in the nation are lymphomas.

Age Patterns

Incidence patterns for different types of cancer in children vary dramatically by age. For example, lymphoid leukemia incidence increases to a peak before age five and declines thereafter, while acute myeloid (nonlymphocytic) leukemia incidence is constant throughout childhood. The incidence of Hodgkin's lymphoma increases throughout childhood and is highest in adolescence. Neuroblastoma, retinoblastoma and Wilms' tumor incidence rates are highest between birth and age one and decline with increasing age.

Risk Factors

Overall, the causes of most childhood cancers remain unknown, but much research is under way to understand factors which could lead to prevention of these diseases. Many types of pediatric cancers are known to be related to genetic conditions. There also has been considerable research into the effects of environmental contaminants, such as pesticides and industrial chemicals, on childhood cancers. The childhood cancers that have been associated in several studies with such environmental factors include leukemias, central nervous system cancers, lymphomas, and Wilms' tumor.

In practice, it is difficult to establish causal relationships, and epidemiologists assess causality carefully before recommending public health activities. The criteria for causation include the strength and consistency of association, the sequence of events (cause before effect), a dose-response relationship (increasing risk with increasing exposure), and the biological plausibility of the association. While all of these criteria need not be satisfied before causality is inferred, they do provide a framework for making inferences from epidemiologic data.

Most statements about risk factors are not definitive, but are more descriptive of the current weight of evidence. Discussions of risk factors in this report largely follow what has been presented in National Cancer Institute and American Cancer Society publications and in review articles by recognized authorities on childhood cancer. When an individual study has been particularly important in understanding a risk factor, we cite that study.

Data Reported

This report presents incidence data for children residing in New Jersey at the time of diagnosis from birth through age 14 during the period 1979-1995 and data from the Surveillance, Epidemiology and End Results (SEER) program of the National Cancer Institute (NCI) for the period 1979-1994. Mortality data for both New Jersey and the United States are reported for the period 1979-1994. All rates presented are per 100,000 children. This report includes figures illustrating trends for all race and sex groups combined and tables showing age-adjusted rates by sex, race and county.

The age classification for children i.e., through age 14, conforms to the standard definition of childhood cancer in the United States and, as such, enables comparisons to be made with other regions. The SEER data are derived from approximately 10 percent of the United States population. Although both the state and national rates presented here are adjusted for differences in age distribution, there are other factors not accounted for such as race/ethnicity, access to health care, and urban/rural status which may limit our ability to make meaningful comparisons.

Whenever a disease is rare, its rates of occurrence fluctuate greatly from year to year and from place to place due to chance and other factors. In order to smooth over the most extreme fluctuations, the graphs of trends are presented as three-year rates statistically centered on each year.

As with all cancers among New Jersey residents, those diagnosed among children must be reported by law to the New Jersey State Cancer Registry within six months of diagnosis. New Jersey has reciprocal agreements with Pennsylvania, New York, Delaware, Florida and several other states to ensure that diagnoses among New Jersey residents which occur out of state are reported. However, these reports may be received at a later date than cases diagnosed and treated within New Jersey. In order to assure data reliability, this report does not include the year 1996 because some 1996 pediatric diagnoses may not yet have been reported to New Jersey from out of state hospitals.

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