S0244 Risk of Gastrointestinal Malignancies in Dermatomyositis and Polymyositis: A Population-Based National Study

Abstract

INTRODUCTION: Dermatomyositis (DM) and polymyositis (PM) are idiopathic inflammatory myopathies that have long been associated with various types of malignancies as possible paraneoplastic responses to oncogenesis. We conducted a population-based national study to evaluate the prevalence of pancreatic, gastric and colorectal cancer diagnosis simultaneously with or within 5 years after the diagnosis of DM or PM in the United States (US) utilizing a large database. METHODS: We queried a commercial database (Explorys Inc, OH), an aggregate of EHR data from 26 major integrated healthcare systems in the US from 1999 to 2020. Using Systematized Nomenclature of Medicine-Clinical Terms, we identified a cohort of eligible patients with a diagnosis of DM or PM between May 2015 and May 2020, followed by the diagnosis of primary malignant neoplasm of pancreas, stomach or large intestines the same day of or within 5 years after the diagnosis DM or PM. Patients with a history of any of these three malignancies were excluded. We also studied potential risk factors (age, gender, and race) for gastrointestinal (GI) malignancies among individuals with DM or PM. RESULTS: Of the 19,370 patients in the database diagnosed with DM or PM, 140 patients were diagnosed with pancreatic cancer, gastric cancer or colorectal cancer. The prevalence of these malignancies was 0.72% in comparison to 0.43% in the population without DM or PM, with OR of 1.71 (95% CI: 1.45–2.02, P < 0.0001). The prevalence is similar (both about 0.7%) with DM and PM when calculated separately. Moreover, individuals with DM or PM who were diagnosed with GI malignancies were more likely to be age > 65 years (OR 2.94, 95% CI: 2.04–4.25). We did not find gender or race to be associated with increased rate of GI malignancy (Table 1). Among patients age 50 years or above, the prevalence of GI malignancy at 10-year age interval are shown in Figure 1. CONCLUSION: We found that patients with DM or PM were almost twice as likely to be diagnosed with pancreatic, gastric or colorectal cancer at the time of or within 5 years after their DM or PM diagnosis. Our result could be an underestimate of this correlation as GI malignancy cases diagnosed before DM or PM were not included in our study. Among individuals with DM or PM, those age >65 years have a significantly increased rate of these malignancies.Table 1.: Potential risk factors (age, gender, and race) for GI malignancies among individuals with DM/PMFigure 1.: Prevalence of GI malignancy at 10-year age interval among DM/PM patients age 50 years or above.