Small Study Ties Ritalin To Higher Cancer Risk

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Small study ties Ritalin to higher cancer risk
Scientist hopes a larger look at drugs that treat attention deficit will refute results

By TODD ACKERMAN
Houston Chronicle - February 24, 2005

In a small but potentially alarming new study, local scientists have linked the most popular drug used to treat attention-deficit problems with increased risks of cancer.

The study of 12 children on Ritalin found every one experienced a significant increase in their level of chromosome abnormalities — occurrences associated with increased risks of cancer and other adverse health effects.

"Assuming it holds up, this study doesn't mean these kids are going to get cancer, but it does mean they're exposed to an additional risk factor," said Marvin Legator, a professor of environmental toxicology at the University of Texas Medical Branch at Galveston and the study's principal investigator and senior author. "Smoking doesn't mean you'll get cancer. It's a risk factor."

But Legator said the study was too small for Ritalin to be considered a risk factor for cancer yet. He said he hopes larger studies refute the finding.

The study is the first to look at the potential chromosome-damaging effects associated with methylphenidate, the generic name for Ritalin, the most widely prescribed drug used to treat attention deficit/hyperactivity disorder (ADHD). Between 1991 and 1999, U.S. sales of Ritalin and its variants, including Concerta and Metadata CD, increased more than 500 percent.

The study, conducted by researchers at UTMB and UT M.D. Anderson Cancer Center, will be published in an upcoming edition of the journal Cancer Letters. It was made available online Thursday.

Other medications cited
The study is just the latest to cast doubt on ADHD medication. Earlier this month, Canadian regulators suspended sales of Adderall amid reports of 20 deaths of patients, including 12 children, taking the drug between 1999 and 2003. In the same time period, American regulators logged seven sudden deaths of children taking Ritalin and Concerta. A third ADHD drug, Strattera, can cause severe liver injury.

In the study, researchers drew blood from children diagnosed with ADHD before they began taking Ritalin and again three months after, then employed a method of analysis that has detected 48 of the 53 known carcinogens in humans. All the children — 10 boys and 2 girls averaging 8.5 years old — were taking normal doses.

For all 12, blood analysis tests showed a twofold to threefold increase in abnormalities in the chromosomes, the bodies within cells that carry genes and genetic information. Most consisted of chromosome breaks, which are associated with an increased risk of cancer.

All people have chromosome abnormalities, typically about 1 percent. The children in the study had levels increased to 2 to 3 percent.

Legator said he was amazed by the consistency of the findings, that all 12 children showed the same result. But he and other investigators stressed that more research needs to be done — for instance, researchers didn't follow up so it's not known whether the chromosome abnormalities are permanent or go into repair once the patient goes off the drug.

Follow-up study planned
Study investigators said parents should respond cautiously to the study and not take their child off Ritalin if he or she is doing well. But Melissa Bondy, an M.D. Anderson epidemiologist who was part of the study, said she understood parents' natural reaction.

"My child was recently diagnosed with ADHD and it was very difficult to decide to use medication after knowing these results," said Bondy. "That's why we need to do further research."

The investigators said they plan to propose a follow-up study with hundreds of patients, multiple sites and longer study periods. Although there are millions of children on Ritalin, participation is limited by the need to enroll patients before they start treatment.

ADHD, the most common neurobehavioral disorder in childhood, affects 4 to 12 percent of U.S. school-age children. Symptoms include short attention span, impulsive behavior and difficulty focusing.

todd.ackerman@chron.com