Cancer in myositis

Abstract

There is an intriguing relationship between cancer and myositis. The immunosuppressive agents commonly used to treat myositis patients are known to favor the development of cancer, but this factor does not seem to be the main cause of the association. Most myositis patients who develop cancer are considered to have cancer-associated myositis, which suggests that there are some types of etiopathogenic relationship between these two conditions. The malignancy usually appears within 3 years of the myositis diagnosis, and the risk of cancer depends on the myositis phenotype, with classic or amyopathic dermatomyositis (DM) and immune-mediated necrotizing myopathy being the main associated phenotypes. Several considerations regarding the pathogenesis of this association and strategies to detect occult malignancy in these patients are discussed here, with special emphasis on the role of autoantibodies as markers of this condition. Anti- TIF1g (Transcription Intermediary Factor 1 gamma) antibodies have been extensively studied in patients with cancer-associated DM. In addition, we discuss the peculiarities of treating patients with cancer-associated myositis and suggest some good treatment options, and finally, we examine the cancer–myositis relationship with regard to the recently described concept of myositis as an immune-related adverse event derived from the use of checkpoint immune inhibitors to treat cancer.