Research article
Predictors of survival in a cohort of patients with polymyositis and dermatomyositis: effect of corticosteroids, methotrexate, and azathioprine
Arthritis Research & Therapy 2012, 14:R22 doi:10.1186/ar3704
Published: 27 January 2012Abstract (provisional)
Introduction
The idiopathic inflammatory myopathies are rare diseases for which data regarding the natural history, response to therapies, and factors affecting mortality are needed. We performed this study to examine the effects of treatment and clinical features on survival in polymyositis and dermatomyositis patients.
Methods
160 consecutive patients (77 polymyositis, 83 dermatomyositis) seen at the University of Michigan (1997-2003) were included. Medical records were abstracted for clinical, laboratory, and therapeutic data, including initial steroid regimen and immunosuppressive use. State vital records were utilized for mortality and cause of death data. Survival was modeled by left-truncated Kaplan-Meier estimation and Cox regression.
Results
5- and 10-year survival estimates were 77% (95% CI 66, 85), and 62% (95% CI 48, 73), respectively; rates were similar for polymyositis and dermatomyositis. Survival between sexes was similar through 5-years, and thereafter significantly lower for males (10-year survival: 18% male, 73% female; p=0.002 for 5-10 year interval). The sex disparity was restricted to the polymyositis group. Increasing age at diagnosis and non-white race were associated with lower survival. Intravenous versus oral corticosteroid use was associated with a higher risk of death among whites (hazard ratio 10.6, 95% CI 2.1, 52.8). Early survival was similar comparing patients treated with methotrexate versus azathioprine, but survival at 10 years was higher for the methotrexate-treated group (76% vs. 52%, p=0.046 for 5-10 year interval).
Conclusions
Patients treated initially with intravenous corticosteroids had higher mortality, likely related to disease severity. Both methotrexate and azathioprine showed similar early survival benefit as first line immunosuppressives; survival was higher between 5-10 years in the methotrexate-treated group but could not be confirmed in multivariable modeling for the full follow-up period. Other important predictors of long-term survival included younger age, female sex, and the Caucasian race.