Cancer rate 4 times higher in children with juvenile arthritis
New research reports that incident malignancy among children with juvenile idiopathic arthritis (JIA) is four times higher than in those without the disease. Findings now available in Arthritis & Rheumatism, a journal published by Wiley-Blackwell on behalf of the American College of Rheumatology (ACR), suggest JIA treatment, such as tumor necrosis factor (TNF) inhibitors, does not necessarily explain the development of cancer in this pediatric population.
Children with JIA experience symptoms similar to adults with arthritis including joint pain, swelling, tenderness and stiffness. JIA is a general term used to describe the various chronic arthritis diseases in children and affects roughly 294,000 under the age of 17 in the U.S. according to a 2008 report from the National Arthritis Data Workgroup.
One of the drug types used to treat childhood and adult arthritis, along with a number of other rheumatic conditions, is TNF inhibitors. Studies have reported that more than 600,000 people worldwide have received anti-TNF therapy since their introduction 15 years ago. However, possible cancer risk has been associated with treatment, prompting the U.S. Food and Drug Administration (FDA) to place “black box” warnings of the potential malignancy risk on TNF inhibitors labels.
In the present study Dr. Timothy Beukelman from the University of Alabama at Birmingham and colleagues conducted one of the largest investigations into the rates of incident malignancy among JIA pediatric patients relative to their treatment. Using data from the U.S. Medicaid records from 2000 through 2005, researchers identified 7,812 children with JIA and two comparator groups without JIA; one group with asthma (652,234 children) and the second with attention-deficit hyperactivity disorder (ADHD; 321,821 children).
The team categorized patients’ treatment with methotrexate and TNF inhibitors as “ever” or “never” used, though many children with JIA did not receive either of these treatments during the study. The research team did not have access to detailed medical records, and therefore categorized the identified incident malignancies as “possible,” “probable,” or “highly probable.”
Although cancer is a leading cause of death among children in the United States, childhood cancer deaths are declining.
In the United States, cancer is the second most common cause of death among children between the ages of 1 and 14 years, surpassed only by accidents. More than 16 out of every 100,000 children and teens in the U.S. were diagnosed with cancer, and nearly 3 of every 100,000 died from the disease. The most common cancers in children were leukemia (cancer of the bone marrow and blood) and brain and central nervous system cancers.
Leukemias
In 2005,* 4.1 of every 100,000 young people under 20 years of age in the U.S. were diagnosed with leukemia, and 0.8 per 100,000 died from it. The number of new cases was highest among the 1–4 age group, but the number of deaths was highest among the 10–14 age group.
Children diagnosed with JIA had a total follow-up time of 12,614 person-years with 1,484 children in this group contributing 2,922 person-years of anti-TNF exposure. The team determined that among all children with JIA compared to those without JIA, the incidence rate was 4.4 times higher for probable and highly probable malignancies. Pediatric JIA patients treated with methotrexate without TNF inhibitors had a similarly increased incidence of cancer, which was 3.9 times higher than children without JIA. No probable or highly probable malignancies were identified in patients following any use of anti-TNF during the study period.
In a related editorial published today in Arthritis & Rheumatism, Dr. Karen B. Onel and Dr. Kenan Onel from the University of Chicago state that the Beukelman et al. study indicates that children with JIA may be at increased cancer risk from the disease, but suggests that anti-TNF therapy may not be associated with a further increased cancer risk. Dr. Kenan Onel cautions, “Larger studies in different populations and with longer follow up are required to confirm Dr. Beukelman’s findings.”
What are the most common types of childhood cancer?
Among the 12 major types of childhood cancers, leukemias (blood cell cancers) and cancers of the brain and central nervous system account for more than half of the new cases. About one-third of childhood cancers are leukemias. The most common type of leukemia in children is acute lymphoblastic leukemia. The most common solid tumors are brain tumors (e.g., gliomas and medulloblastomas), with other solid tumors (e.g., neuroblastomas, Wilms tumors, and sarcomas such as rhabdomyosarcoma and osteosarcoma) being less common.
How many children are diagnosed with cancer in the United States annually?
In the United States in 2007, approximately 10,400 children under age 15 were diagnosed with cancer and about 1,545 children will die from the disease (1). Although this makes cancer the leading cause of death by disease among U.S. children 1 to 14 years of age, cancer is still relatively rare in this age group. On average, 1 to 2 children develop the disease each year for every 10,000 children in the United States (2).
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Selected References
American Cancer Society. Cancer Facts and Figures 2007. Atlanta, GA: American Cancer Society.
Ries LAG, Melbert D, Krapcho M, et al. SEER Cancer Statistics Review, 1975–2004. Bethesda, MD: National Cancer Institute.
The editorial authors point out that most patients in this study were treated with etanercept, a soluble TNF receptor blocker, and the investigation of other anti-TNF agents working by different mechanisms may yield different results. Nonetheless, Dr. Onel argues, “By focusing on the possible cancer risk associated with the use of TNF inhibitors, the underlying cancer risk associated with JIA may have been understated, and it is important to make patients, families, and physicians aware of the possible late consequences of this disease.”