The risk of developing leukemia as a side effect of a drug for multiple sclerosis is higher than previously reported, according to a study presented at the 61st Annual Meeting in Seattle.

Mitoxantrone ( Novantrone ) is an immunosuppressant drug approved by the FDA ( Food and Drug Administration ) for treatment of several forms of advancing multiple sclerosis. It is one of only two drugs that has been shown to benefit people with secondary progressive multiple sclerosis who are having attacks. However, the drug can cause heart damage at high total doses. Due to this, the lifetime cumulative dose is equal to about eight to 12 doses over two to three years.

Previous studies have also shown that the people with multiple sclerosis treated with the drug have an increased risk of developing leukemia. Those studies showed that acute leukemia occurred in 0.07% to 0.25% of multiple sclerosis patients taking Mitoxantrone.

The retrospective study of 2,854 Italian people with multiple sclerosis receiving Mitoxantrone found that leukemia occurred in 0.74%.

According to study author Vittorio Martinelli, of University Vita-Salute in Milan, Italy, this rate is significantly higher than what has been previously reported. The potential risk of leukemia should be carefully considered against the potential benefits of Mitoxantrone treatment on every single patient.

The study participants all had at least one cycle of Mitoxantrone treatment and were observed for at least one year. A total of 21 people developed leukemia, eight of whom died. The people who developed leukemia had more treatment cycles than those who did not develop leukaemia, 8.6 cycles versus 7.2 cycles. They also had a greater cumulative dose of Mitoxantrone.

The leukemia occurred an average of three years after the first use of the drug and an average of 18 months after the end of treatment.

It is vital that all multiple sclerosis patients treated with Mitoxantrone undergo prolonged and careful hematological follow-up to check for acute leukaemia.

Source: American Academy of Neurology, 2009

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