Malignancies in idiopathic inflammatory myopathies: pathogenesis, epidemiology, and current practice

Malignancy is a major cause of mortality and morbidity in patients with idiopathic inflammatory myopathies (IIM).Previous large-scale cohorts have shown that IIM patients have a significantly increased risk for cancer.The incidence is highest at the time of the IIM diagnosis, suggesting that appropriate screening for cancer in patients with IIM is an important step to improve the prognosis of patients.However, no consensus has been reached regarding an optimal cancer screening strategy.Although several studies have investigated potential risk factors for cancer in patients with IIM, the effects of some clinical factors appear to differ according to patient's race, country, and other characteristics.In this article, we review immunologic alteration associated with cancer in IIM and the epidemiologic features of myositis-associated cancer.We also review the clinical factors that potentially influence cancer risk and examine variations according to country and ethnicity.Finally, we summarize the first-published consensus-based guideline for cancer screening published by International Myositis Assessment and Clinical Studies Group and discuss future research direction toward developing an optimal cancer screening strategy for patients with IIM.