Malignancy in dermatomyositis and polymyositis: analysis of 192 patients

This study aims to investigate the prevalence and predictive risk factors of malignancy in patients with polymyositis (PM) and dermatomyositis (DM). The medical records of 192 PM/DM patients followed up in a medical center between January 2000 and December 2013 were reviewed. Among the 192 patients, 33 patients (17.2 %) had associated cancer. Both PM and DM are significantly associated with cancer, although the risk of cancer appears to be somewhat higher among patients with DM (23.0 %) than among those with PM (8.9 %). Nasopharyngeal cancer (30.3 %) and breast cancer (18.2 %) comprised the most common malignant diseases associated with PM/DM. Univariate analysis showed that an older age at PM/DM onset, heliotrope rash, Gottron's sign, dysphagia, and low creatine phosphokinase (CPK) level were associated with increased malignancy. Multivariate analysis revealed that independent predictors of malignancy in PM/DM were age >40 years at PM/DM onset (adjusted OR 3.44; 95 % CI 1.08-10.98; p = 0.037) and heliotrope rash (adjusted OR 2.96; 95 % CI 1.04-8.43; p = 0.042). During the follow-up period, 66 (34.4 %) patients died and the overall patient survival rates were 83.1 % at 1 year, 78.9 % at 2 years, 74.2 % at 5 years, and 65.5 % at 10 years. This study demonstrates a high frequency of malignancy (17.2 %) in DM/PM patients. Nasopharyngeal cancer and breast cancer were the most common cancer types in DM/PM patients in our study. Cancer screening should be offered to patients with newly diagnosed DM/PM. Moreover, all patients should be evaluated for the possibility of an underlying malignancy during treatment.