Objectives: We aimed to explore the incidence of malignancy in dermatomyositis and assess the potential risk factors of occurrence of malignancy in DM from southern China.
Methods: A retrospective cohort study of patients admitted in the 1st affiliated university hospital between 2003 and 2012 was performed. Demographic information, clinical symptoms, laboratory findings, medications were documented. The endpoint of the study was defined as occurrence of malignancy or death.
Results: For this approximately 10-year retrospective study, 60 out of 246 dermatomyositis patients developed malignancies with the overall incidence of 24.4%. Nasopharyngeal carcinoma (NPC) and ovarian carcinoma were the most common malignant disease, accounting for 35% (21/60) and 15% (9/60) of malignancies, respectively. Lung and colon were followed as the third most common carcinoma (5 out of 60, 8.3%). Among these 60 patients with malignancies, 39 (65.0%, 39/60) cases occurred within 1 year after DM diagnosis. Subsequently, malignancies were detected in 13 (21.7%, 13/60) patients during the second year and 8 (13.3%, 8/60) during the third year. One patient developed cancer at the 35th month after DM as the latest. The logistic regression multivariate analysis indicated that male gender [odds ratio (OR) = 3.76, 95% confidence interval (CI ) 1.86~7.61, p<0.01], dysphagia (OR= 2.21, 95%CI 1.10~4.48, p=0.03) and elevated erythrocyte sedimentation rate (ESR) (OR= 2.37, 95% CI 1.18~4.75, p=0.02) were risk factors for the occurrence of malignancies, while interstitial lung disease (ILD) acted as a protective factor (OR=0.13, 95%CI 0.06~0.28, p<0.01).
Conclusions: It was necessary to carry out routine malignancy screening for Chinese DM patients due to its high incidence. Nasopharyngeal carcinoma and ovarian cancer were the most common malignant disease. The risk of malignancy was highest in the first year after DM diagnosis and reduced thereafter. Extensive work-ups for malignancy screening should be carried out at the first year. Male gender, dysphagia and elevated ESR were risk factors for occurrence of malignancy. The presence of ILD could diminish the risk of coexisting of malignancy.