Children, Cancer & The Environment

Children, Cancer & The Environment Main Page Common Causes The Most Common Cancers Protecting Your Children Q&A

How common is childhood cancer in the United States?

Childhood cancer is relatively rare -- only about 2 percent of all cancer cases occur in children. Each year, about one out of every 15,000 children gets cancer. In 1998, the most recent year for which we have data, about 12,400 U.S. children under 20 were found to have cancer. That same year, 2,500 children died from the disease.

Rates of childhood cancer have risen over the past few decades, so the disease is more common now than it once was. Cancer kills more children than any other disease, and is the second most common cause of death in children, behind injuries. But while the number of new cases of childhood cancer has risen, the death rate has decreased for most forms since 1970, largely because of improved treatments.

Is childhood cancer increasing?

It is clear that childhood cancer increased significantly from the early 1970s to the early 1990s, rising about 1 percent each year during those two decades. Since the 1990s, rates of childhood cancer seem to have leveled off, but there is no evidence of a decline back to pre-1980 rates. The reason for the dramatic increase in childhood cancers during the seventies and eighties is still unclear. But many researchers feel that genetic factors and improved diagnosis fail to explain it, making environmental factors the most likely cause.

How do childhood and adult cancers differ?

Children's cancer is not only less frequent than adult cancer, it is also different. None of the most common adult cancers -- prostate, breast, lung, colon -- are found in children. Instead, children tend to get leukemias, brain tumors and other cancers of the blood and connective tissues. Adult cancers are thought to occur because of years of cumulative damage to the cells. In children, this kind of long-term damage has not had a chance to take place. Their cancers are thought to occur, instead, during periods of vulnerability during early development, when the organs are still forming.

At what age does childhood cancer most often occur?

Childhood cancer most often strikes very young children. For that reason, even though it causes a relatively small number of deaths, childhood cancer leads to many years of lost life -- about 70 per child who does die. Forty percent of cases occur in children under five, with most occurring in children less than a year old. The frequency of cancer then decreases, but rises again when children reach adolescence.

Which cancers affect children most often?

Leukemia is the most common childhood cancer, representing 31.5 percent of cases in children under 15. Next most common are central nervous system cancers including brain cancer (20.2 percent), lymphomas including Hodgkin's disease and non-Hodgkin's lymphoma (10.7 percent), neuroblastoma and other cancers of the nerves (7.8 percent), soft tissue sarcomas (7 percent), kidney cancers (6.3 percent) and cancer of the bones (4.5 percent).

The patterns of these cancers vary by age. For infants, neuroblastoma is the most common form, accounting for 28 percent of cases. Leukemia (17 percent), central nervous system cancers (13 percent), retinoblastoma (12 percent) and Wilms tumor (9 percent) are the next most common. For children up to 15 years, the most common cancers are leukemia, brain and central nervous system cancers, lymphoma, soft tissue sarcomas, kidney tumors and cancer of the bones.

What is the survival rate for childhood cancer?

For most forms of childhood cancer, the survival rate is high. Mortality (death) rates have decreased dramatically since the 1970s as a result of improved treatment. An important exception is brain cancer. Death rates for this form have actually climbed in recent years.

What are the effects of cancer treatment?

Today, the most important effect of cancer treatment is that children are likely to be cured. But treatments for childhood cancer may lead to other health effects later in life, including developmental effects, other cancers, organ damage, hormonal problems, infertility and premature death. And, of course, there is another effect, much harder to measure: the anguish and disruption cancer treatment causes not only for children, but also for their families.

Is childhood cancer caused by genetic or environmental factors?

Childhood cancer doesn't usually run in families, and there is little evidence for a strong genetic predisposition. Evidence does exist, however, for environmental links with childhood cancer. But it will most likely turn out that both genetic and environmental factors are involved. For example, some children may have genetic predispositions toward cancer that are triggered by environmental exposures, or they may be less able to tolerate exposure to a toxic or cancer-causing chemical. This may explain why some children who are exposed to hazardous substances develop cancer, while many others do not.

What are the links between pesticides and childhood cancer?

Numerous research studies have uncovered links between pesticide exposure and childhood cancer. Most of the research has focused on leukemia and brain tumors, and the majority of the studies have found connections with pesticides. However, there are many uncertainties. For example, not all studies identified a link with pesticides, and the studies that did find a link were usually unable to identify the particular chemical that might have been responsible; instead, they found links with insecticide use generally, or with working on a farm. It also remains unclear if there are certain people who are more susceptible, and if there are certain times of life during which children are most vulnerable. Because of these uncertainties, it is difficult to be sure what to protect children from. The best course is to decrease or eliminate any unnecessary pesticide exposures.

What other environmental exposures may cause childhood cancer?

Research has linked childhood cancer to numerous environmental factors. Some of these may occur before the child is even born. For example, parents who were exposed to solvents (such as paint thinners, degreasers, glues or gasoline) on the job are more likely to have children who develop leukemia or brain tumors. A few studies have found possible links between exposure to electromagnetic fields and childhood leukemia, although these results are contradicted by several good studies that found no such link. Ionizing radiation (such as that produced by nuclear bombs, nuclear power plants, and X-rays) is a known cause of childhood cancer. Other likely links include cigarette smoke and radon gas.

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last revised 4.10.02