The incidence of childhood leukemia is rising among white Hispanic children in the United States, according to researchers from the University of California system.
Researchers analyzed data obtained from the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute, which provides statistical information about cancer in the United States. The data on childhood leukemia, collected between 1992 and 2013, suggests that the incidence of leukemia has significantly increased among white Hispanic children. There was no significant increase in the incidence of leukemia among non-Hispanic white, non-Hispanic black, and non-Hispanic Asian children. Data from Hispanic children of other races (black, Asian, etc.) was not included in this study.
The work, conducted by researchers from the University of Southern California, the University of California Berkeley, and the University of California San Francisco, has been available in the International Journal of Cancer since late 20161.
What is leukemia?
The National Cancer Institute defines leukemia as a cancer of the blood cells. Leukemia is the most common cancer in children, defined here as people 0-19 years of age. The cause of childhood leukemia is unknown and there are few risk factors associated with the disease. Scientific evidence has identified a weak genetic basis for the increased risk of childhood leukemia, but most leukemia is not linked to any genetic risk factors.
There are four primary types of leukemia; two are acute, and two are chronic. In acute leukemia, blood cells form blasts, or immature cells that cannot perform their normal function. With acute leukemia, the number of blasts increases rapidly, and the disease progresses quickly. The two primary forms of acute leukemia are acute lymphocytic leukemia (ALL) and acute myeloid leukemia (AML). ALL is the most common form of childhood leukemia, but can also affect adults, especially the elderly. AML occurs both in children and adults. Both ALL and AML leukemia were examined in this study.
In chronic leukemia, the blasts are usually more mature and some can perform their normal function. The number of blasts does not increase as quickly. Consequentially, chronic leukemia becomes gradually worse. The two primary types of chronic leukemia are chronic lymphocytic leukemia (CLL) and chronic myeloid leukemia (CML). CLL is most common in adults over 55 years old. CLL sometimes affects young adults, but almost never children. CML occurs almost exclusively in adults, although a very small percentage of CML patients are children. For more information on these cancers, please visit the Cancer Treatment Centers of America2.
Cases of childhood leukemia are increasing, particularly among white Hispanic children
According to the study, childhood leukemia has increased among all children in the United States at an average rate of 1% per year since 1973, but is highest among Hispanic children. Although the incidence of all types of leukemia in white Hispanic children has increased only 0.96% a year between 1992 and 2013, the incidence of ALL in Hispanic children has increased at an average rate of 1.08% a year. ALL incidence in white Hispanic children 10-14 years old increased by 2.09%, 15-19 year olds by 2.67%, and 1.56% in white Hispanic females of any age. Oppositely, AML incidence has decreased in all white Hispanic children except those less than 1 years old (increasing at a rate of 4.29% a year) and children 1-4 years old (increasing at ate rate of 3.13% a year).
Incidence of childhood leukemia is highest among white children
The incidence rate of all types of leukemia, ALL, and AML among white Hispanic children was 6.05, 4.89, and 0.97 per 100,000 children respectively during the years 2009-2013. This is compared to non-Hispanic white children (4.45, 3.44, 0.87), black children (2.62, 1.83, and 0.67), and Asian children (4.21, 2.97, 1.04) respectively. Although not emphasized in the study, white children appear to have greater incidence of childhood leukemia than children of other races. Between 2009 and 2013, 36.7% of childhood leukemia diagnoses were in white Hispanic children, and 43.4% in non-Hispanic white children. Black and Asian children comprised much less (7.6% and 8.2% respectively) of childhood leukemia diagnoses.
Why are Hispanic children so susceptible to leukemia?
Tobacco use, body weight, diet, and physical activity are risk factors for leukemia and most adult cancers. However, children are unlikely to have adopted any of these lifestyle risk factors. There are very few known risk factors for childhood leukemia, though parental tobacco use, high birth weight, and exposure to toxins such as paint are contributing factors.
There are very few studies that explain the prevalence of leukemia in Hispanic children. Researchers in the study suggest that some genes may affect the metabolism of environmental toxins, such as pesticides. Hispanic children either live in close proximity to such toxins, or are more susceptible to their deleterious effects when compared to children of other race. In particular, Hispanic children are disproportionately likely to live near or within farming communities. Occupational exposure to agricultural chemicals in vitro or in early childhood may contribute to increased leukemia incidence. Current explanations are speculative at best, and further experiments are required for a more veritable answer.
Cancer is one of the greatest medical challenges of modern society. Understanding the ethnic, geographic, and socioeconomic risk factors can help develop more powerful, targeted treatments against the disease, especially in children, who are unlikely to have any of the lifestyle risk factors associated with adult cancers.
- Barrington-Trimis et al. Trends in childhood leukemia incidence over two decades from 1992 to 2013. Int J Cancer (2016). E-pub ahead of print. DOI: 10.1002/ijc.30487.
- Leukemia types. National Cancer Treatment Centers of American Link.