Survival analysis of patients with dermatomyositis and polymyositis: analysis of 192 Chinese cases

Abstract

To estimate the mortality rate and identify factors predicting survival in patients with polymyositis (PM) and dermatomyositis (DM). The medical records of 192 PM/DM patients who were treated at Chang Gung Memorial Hospital from 1999 through 2008 were retrospectively reviewed. The Taiwan National Death Registry (1999-2008) was used to obtain their survival status. Thirty-one (16.1%) of the 192 patients with PM/DM had an associated malignancy; 41 (21.4%) had interstitial lung disease (ILD). During the follow-up period, 55 (28.6%) patients died and the overall cumulative survival rate was 79.3% at 1 year, 75.7% at 2 years, 69.9% at 5 years, and 66.2% at 10 years. In univariate analysis, older age at PM/DM onset, anemia, thrombocytopenia, leukopenia, diabetes mellitus, ILD, cancer, and non-use of azathioprine were associated with higher mortality (p = 0.0172, 0.0484, <0.0001, 0.0008, 0.0001, 0.0036, 0.0010, and 0.0019, respectively). In multivariate Cox regression analysis, thrombocytopenia (hazard ratio [HR] 4.94, 95% confidence interval [CI] 2.60-9.37, p < 0.0001), diabetes mellitus (HR 2.57, 95% CI 1.38-4.80, p < 0.0001), cancer (HR 2.30, 95% CI 1.26-4.22, p = 0.0030), and ILD (HR 1.98, 95% CI 1.11-3.51, p = 0.0182) were positively associated with mortality. Use of azathioprine (HR 0.35, 95% CI 0.16-0.74, p = 0.0064) was negatively associated with mortality. This study confirmed the high mortality rate (28.6%) in PM/DM patients. Survival time was significantly reduced in patients with thrombocytopenia, diabetes mellitus, ILD, and cancer patients than in those without these conditions.