Do Acute-Phase Reactants Predict Response to Glucocorticoid Therapy in Retroperitoneal Fibrosis?

Objective. To determine the value of the erythrocyte sedimentation rate (ESR) and the C-reactive protein (CRP) level at the time of diagnosis for predicting radiographic response to glucocorticoid therapy in patients with retroperitoneal fibrosis (RFP). Methods. Data were collected retrospectively for 37 patients with an established diagnosis of RFP (the diagnosis was proven by biopsy in 31 patients), all of whom met the following inclusion criteria: 1) availability of a recorded baseline ESR and/or CRP level and results of computed tomography or magnetic resonance imaging, 2) availability of followup CRP level and/or ESR with radiographic imaging 12-24 weeks after initiation of therapy, and 3) treatment with prednisone monotherapy at a starting dosage of 40-60 mg daily. Patients were divided into 2 therapeutic response groups: group 1 showed radiographic regression, and group 2 showed no change or radiographic progression. Any progression or regression was determined by an estimated change of >= 25%. Results. The median baseline CRP levels were 2.2 mg/dl (interquartile range [IQR) 1.4-8.0) in group 1 and 1.2 mg/dl (IQR 0.8-4.1) in group 2 (P = 0.35). The median baseline ESR in group 1 was 57.5 mm/hour (IQR 39.2-102.5), which was not statistically different from the median ESR in group 2 (58 mm/hour [IQR 33-66)). The mean CRP level and ESR tended to be higher in patients with radiographic regression, but these differences failed to reach statistical significance. Spearman's correlation coefficient revealed no correlation between the baseline CRP level (r = -0.11, P = 0.51) or ESR (r = -0.06, P = 0.71) and the radiographic response. Conclusion. The ESR and CRP level at baseline are poor predictors of a therapeutic response to glucocorticoid therapy in patients with RPF.