Cancer and Idiopathic Inflammatory Myositis

Abstract

Here we present an update on best practices and clinical considerations when evaluating IIM patients for malignancy. Idiopathic inflammatory myopathies (IIM) comprise a group of diseases including dermatomyositis (DM), polymyositis (PM), and immune-mediated necrotizing myopathies (IMNM). There is an increased risk of concomitant cancer near the time of myositis onset (cancer-associated myositis, CAM) in unique subsets of IIM patients, particularly those with anti-transcriptional intermediary factor 1-gamma (anti-TIF1-γ), anti-nuclear matrix protein-2 (NXP-2), and potentially anti-3-hydroxy-3-methylglutaryl-coenzyme-A reductase (HMGCR) antibodies. While myositis-specific autoantibodies (MSAs) improve risk stratification for cancer in IIM patients, evidenced-based data continues to be lacking with regard to the optimal cancer assessment and duration. Data has been supportive of the association of certain myositis-specific antibodies with malignancy as mentioned above. The optimal strategy for cancer screening remains under discussion but the highest risk of malignancy appears to be within 1 to 3 years of diagnosis making this an important window to maintain vigilance.