SOURCE: American Academy of Neurology
The multiple sclerosis (MS) drug mitoxantrone may be associated with an increased risk of colorectal cancer, according to a study published in the May 11, 2016, online issue of the journal Neurology.
Mitoxantrone is used for aggressive types of relapsing-remitting or progressive MS that do not respond to other MS drugs. But its use is limited because previous studies have shown an increased risk of leukaemia and heart damage.
The current study examined whether the drug increases the risk of other types of cancer.
Mathias Buttmann, MD, University of Würzburg, Würzburg, Germany, and colleagues looked at all people with MS who were treated with mitoxantrone from 1994 to 2007 and followed them until 2010.
Of the 676 people, 37 people (5.5%) were diagnosed with cancer after taking the drug, including 9 people with breast cancer, 7 with colorectal cancer, and 4 with acute myeloid leukaemia, which has been associated with mitoxantrone.
The rate of leukaemia was 10 times higher in the people treated with mitoxantrone than in the general population in Germany. The rate of colorectal cancer was 3 times higher than that of the general population.
For breast cancer and all other types of cancer, people who had taken mitoxantrone were no more likely to develop the diseases than those in the general population.
Of the 7 people with colorectal cancer, 3 died from the cancer during the study. The 4 people with leukaemia all went into remission after treatment and were alive at the end of the study.
The researchers also looked at whether factors such as how much of the drug people had received cumulatively and whether they also received other immunosuppressant drugs affected their risk of developing cancer. The only factor related to a higher risk of cancer was being older when starting to take the drug.
“Despite an increased risk of acute myeloid leukaemia 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 Dr. Buttmann. “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.”
He noted that the study was relatively small and needs to be confirmed. If the results are confirmed, he said that colonoscopies should be given after treatment with the drug to screen for colorectal cancer, which can be treated more effectively when diagnosed earlier.