A recent study published in the online issue of Neurology, the medical journal of the American Academy of Neurology indicates that the multiple Sclerosis drug mitoxantrone may be associated with an increased risk of colorectal cancer. The drug is prescribed for aggressive types of relapsing remitting or progressive MS that don't respond to other MS drugs. It has previously been linked to an increased risk of leukemia and heart damage so is not widely prescribed.
The study, conducted in Germany examined whether mitoxantrone increases the risk of cancers other than leukemia and involved 676 people who were treated with mitoxantrone from 1994-2007 and were followed until 2010. 37 people (5.5%) were diagnosed with cancer. 9 people were diagnosed with breast cancer, 7 with colorectal cancer and 4 with acute myeloid leukemia. The rate of leukemia was 10 times higher than in the general population, colorectal cancer was 3 times higher and breast cancer had no increased risk over the general population. Because the overall rate of cancer is still low, the study author, Mathias Buttmann, M.D., the use of mitoxantrone may still be justified for people severely affected by MS if there is no better treatment available and that if the results are confirmed colonoscopies should be given after treatment with the drug to screen for colorectal cancer in order to detect and treat it early.