Immunomodulatory Therapy in Multiple Sclerosis and Breast Cancer Risk: A Case Report and Literature Review

Multiple sclerosis (MS) is an autoimmune inflammatory disease of the central nervous system frequently complicated by devastating neurologic symptoms and progressive disability. Much progress has been made in the development of immunomodulating drugs to help fight the progression of MS. These drugs are believed to work by interacting with various immune system components to reduce the amount of autoimmune destruction to the nervous system. We report 2 cases of women with MS on immunomodulatory therapy who presented with locally advanced breast cancer with aggressive biologic phenotypes and exceptionally poor outcomes. We consider the potential for an increased risk of developing a poorer-prognosis breast cancer as a result of concomitant immunomodulatory effects of the previous MS treatment, particularly the effects the drugs are reported to have on regulatory T cells, and therefore present these cases and a review of the current literature. Current data in the literature reflect the need for further study in ascertaining the risk of biologically poor-prognosis breast cancer development in patients with MS treated with immunomodulatory therapy.