Multiple Sclerosis Drug Possibly Linked to Colorectal and Breast Cancer

The multiple sclerosis (MS) immunosuppressant drug mitoxantrone might be linked to an increased risk for breast and colorectal cancer, according to findings published in Neurology.

Researchers from the University of Wurzburg in Germany conducted a retrospective cohort study of mitoxantrone treated MS patients seen between 1994 and 2007 in order to assess the therapy related risk of malignancies in mitoxantrone treated patients with MS. The researchers obtained follow up information about malignancies, life status and cause of death as of 2010.

Then, they compared malignancy rates to the German national cancer registry matched for sex, age and year of occurrence. A total of 676 patients were identified and the median follow up time was nearly nine years.

About 5 percent, or 37 patients were diagnosed with a malignancy after mitoxantrone treatment, which corresponded to a 1.50 incidence ratio, the researchers reported. Some of the malignancies included breast cancer (nine patients), colorectal cancer (seven patients), acute myeloid leukemia (four patients) and others (either one or two patients). The incidence ratio for colorectal cancer was 2.98 and reached 10.44 for acute myeloid leukemia. It did not increase in breast cancer or other entities, the researchers said.

“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,” study author Mathias Buttmann, MD, said 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.”

Throughout the follow up period, there were 55 deaths, of which 12 were due to malignancies and 43 were from other reported causes, the researchers commented.

The researchers added that even though the study was done on a small patient group, if the findings are confirmed, they recommend that colonoscopies be given after treatment with mitoxantrone to screen for colorectal cancer.