Onset of malignancy in patients with idiopathic inflammatory myopathy: a matched cohort study of the NIH’s All of Us program

Dermatomyositis (DM) and polymyositis (PM) comprise a group of autoimmune conditions known as idiopathic inflammatory myopathies (IIM) which can be paraneoplastic. While DM and PM have been associated with malignancy in international cohorts, the strength of this association remains unclear in a nationally representative U.S. cohort. To characterize the association of DM and PM with malignancy, we analyzed 208 DM and 171 PM patients with their matched morphea controls from the NIH’s All of Us program, a large U.S. sample that may reduce variation seen in smaller regional studies. Morphea patients were selected as controls as they often undergo comparable management though typically with lower intensity immunosuppressive treatment relative to DM/PM, thus providing an analysis of malignancy risk attributable to IIM itself rather than chronic immune dysfunction. Our study found that while there was no difference in time to onset of malignancy between DM or PM and their matched control, both DM (p = 0.0304) and PM (p = 0.0380) were associated with increased risk for malignancy compared to their matched controls. Five-year malignancy incidence was 11.9% in DM and 15.9% in PM patients. These findings expand evidence for the association of malignancy with IIM and specifically highlight increased risk among DM/PM patients in a nationally representative U.S. cohort. A thorough understanding of the nuanced relationship between malignancy and autoimmunity remain to be clarified in larger prospective studies.