Leukemia Risk From MS Drug May Be Up

May 1 -- THURSDAY, April 30 (HealthDay News) -- The risk of developing leukemia from a drug used to treat rapidly-progressing multiple sclerosis is three times higher than previously reported, new research shows.

Italian researchers found that for every 1,000 people given mitoxantrone (Novantrone), an estimated 7.4 people will develop acute leukemia, compared with fewer than 2.5 people in prior estimates. Mitoxantrone is an immunosuppressant approved by the U.S. Food and Drug Administration for treatment of secondary progressive MS.

In the study, about 0.74 percent of people taking the drug developed leukemia. Previous research had put the risk of leukemia at .07 to .25 percent.

This rate is significantly higher than what has been previously reported, said study author Dr. Vittorio Martinelli of University Vita-Salute in Milan.

The potential risk of leukemia should be carefully considered against the potential benefits of mitoxantrone treatment on every single patient, Martinelli urged in a summary of his research, which is to be presented Thursday at the American Academy of Neurology's annual meeting, in Seattle.

Mitoxantrone is one of the only drugs that has been shown to benefit people with a secondary progressive MS who are having attacks of symptoms that include numbness, loss of balance, difficulty walking, fatigue, vision problems and impaired thinking.

In Martinelli's study of 2,854 people with multiple sclerosis, 21 have developed acute leukemia, and eight have died.

About 85 percent of people diagnosed with MS begin with a relapsing-remitting course, in which attacks are followed by partial or total recovery, according to the National Multiple Sclerosis Society.

More than 60 of those go on to develop secondary progressive MS, in which symptoms worsen over time, and there are fewer, shorter periods without symptoms. Eventually the disease can lead to loss of vision and paralysis.

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.