Mitoxantrone, a Drug for Progressive and Severe Relapsing MS, Linked to Colorectal Cancer Risk

Mitoxantrone,  a multiple sclerosis (MS)  drug that is already associated with a higher risk for leukemia and heart damage, may also raise a person’s risk of colorectal cancer, researchers at the University of Würzburg, in Germany, reported. If confirmed in larger studies, the findings indicate that colonoscopies should be conducted on MS patients after mitoxantrone treatment to monitor them for this cancer.

The article, “Malignancies after mitoxantrone for multiple sclerosis: A retrospective cohort study,” was published in the journal Neurology.

Mitoxantrone is prescribed to patients with progressive MS, a notoriously difficult-to-treat MS subtype, and aggressive types of relapsing-remitting MS that do not respond to other treatments. First developed as a chemotherapy, the drug was approved in 2000 for MS because it powerfully suppresses the immune system.

In a retrospective study into the risk of malignancies related to the drug, researchers analyzed clinical data from mitoxantrone-treated MS patients between 1994 and 2007, and collected data on confirmed malignancies, life status, and cause of death as of 2010.

Of the 676 patients analyzed, 37 (5.5%) were diagnosed with cancer after mitoxantrone treatment initiation, including nine people with breast cancer, seven with colorectal cancer, and four with acute myeloid leukemia. Compared with the German national cancer registry matched for sex, age, and year of occurrence, the rate of leukemia was 10 times higher in mitoxantrone patients. For colorectal cancer, the rate was three times higher among treated patients. No increased risk for breast cancer and other malignancies was associated with mitoxantrone. Three of the people diagnosed with colorectal cancer died during the study.

Researchers also found that the incidence of colorectal cancer and leukemia was not increased by factors such as drug dose, gender, or treatment with other immunosuppressant drugs. Only older age was related to a higher risk for cancer.

Still, the authors believe that mitoxantrone is a valuable therapy for MS patients.

“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,” said Mathias Buttmann, MD, the study’s first author, in a press release. “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.”