Significant Toxicity of Mitoxantrone in Patients With Multiple Sclerosis: Cancer

Following a median follow-up of more than 8 years, researchers in Germany have discovered that mitoxantrone—used to treat aggressive, relapsing, or progressive multiple sclerosis (MS)—can increase the risk of leukemia and colorectal cancer (CRC) in those being treated.

Published in the journal Neurology, the authors of the study conducted by researchers at the

University of Würzburg in Germany, retrospectively observed 677 patients who were administered mitoxantrone for their MS, between 1994 and 2007. Follow-up data, gathered till 2010 for 676 patients, included malignancies, life status, and cause of death.

During the median follow-up period of 8.7 years (interquartile range, 6.8-11.2), 37 patients were diagnosed with a malignancy: either breast cancer (9 patients), CRC (7 patients), acute myeloid leukemia (AML, 4 patients), or other (1 or 2 patients). Following a comparison with the German national cancer registry, the authors reported standardized incidence ratio of CRC at 2.98 (95% CI, 1.20-6.14) and of AML 10.44 (95% CI, 3.39-24.36). Of the reported 55 deaths, 12 patients died of a malignancy.

Risk factors, the authors found, included age at treatment initiation as a significant risk factor for developing malignancies. Sex, cumulative dose of mitoxantrone, or treatment with other immunosuppressive agents did not seem to play a role in increasing the patient’s risk of developing a malignancy.

Explaining the significance of their findings, lead author Mathias Buttmann, MD, of the University of Würzburg, said in a statement, “Despite an increased risk of acute myeloid leukemia and colorectal cancer, the overall rate of cancer was low enough to justify still using this drug for people severely affected by MS if no better treatment is available. Mitoxantrone is the only approved treatment for people with secondary progressive MS without relapses and should be considered in people where the disease is evolving quickly. Also, many of the new and highly effective MS drugs are not available to people in a number of countries for economic reasons, so mitoxantrone is being used for people with very active relapsing forms of the disease.”

Citing the small sample size of their study as a limitation, Buttmann advised that additional studies are needed to confirm their findings. He also recommended that if their results are confirmed, patients being treated with mitoxantrone should undergo colonoscopy so they would be diagnosed earlier.

Reference

Buttmann M, Seuffert L, Mäder U, Toyka KV. Malignancies after mitoxantrone for multiple sclerosis [published online May 11, 2016]. Neurology. doi:http:/​/​dx.​doi.​org/​10.​1212/​WNL.​0000000000002745.