Because research has shown that the drug can cause heart failure at high cumulative dosages as well as acute leukemia, doctors exercise caution when giving it to patients, said Patricia O'Looney, vice president of biomedical research for the National Multiple Sclerosis Society.
But the difficulty, she said, is that there are few other options for people with secondary progressive MS, and quality of life has to be balanced with risk of heart damage and leukemia.
"That's the frustrating part," O'Looney said. "When someone is reaching a very progressive form of the disease, and other drugs aren't working, we desperately need something in the clinical care of patients to try to help them. But there's no question about it. Novantrone is a strong drug, and with strong drugs, there are side effects."
Mitoxantrone is given in an IV infusion, usually in doses of 10 to 20 milligrams spaced about thee months apart.
Current U.S. guidelines call for people to receive a total lifetime dose of no more than 140 mg, O'Looney said.
People in the Italian study had received substantially less. Those who developed leukemia were given an average of 82 mg, compared with 63 mg for those who did not develop leukemia.
The leukemia occurred an average of three years after the first use of the drug and an average of 18 months after treatment had ended, according to the study.
"It is vital that all MS patients treated with mitoxantrone undergo prolonged and careful hematological follow-up to check for acute leukemia," Martinelli said.
In a second study to be presented at the meeting in Seattle, researchers found that adding the steroid methylprednisolone to treatment with interferon beta-1a (Avonex), a standard part of MS drug therapy, may reduce the amount of disease activity more than using the MS drug alone.<
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