Value of acute-phase reactants in monitoring disease activity and treatment response in idiopathic retroperitoneal fibrosis.

BACKGROUND Prospective evaluation of the value of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels in monitoring disease activity and treatment response in patients with idiopathic retroperitoneal fibrosis (RPF). METHODS This study included 57 patients with idiopathic RPF receiving tamoxifen monotherapy with at least 8 months follow-up. Clinical, laboratory and radiological investigation was performed at presentation and at repeated follow-up. Remission was defined as significant clinical improvement within 6 weeks of treatment together with stable or decreasing mass size on follow-up computed tomography (CT) scanning at 4 months and definitive decrease in mass size on follow-up CT scanning at 8 months. RESULTS ESR and CRP levels at presentation and their respective decreases over time correlated strongly with each other (P<0.001). Baseline ESR and CRP levels correlated with visual analogue scale (VAS) score for pain (ESR, P<0.01; CRP, P<0.001); baseline ESR levels also correlated with VAS score for discomfort (P<0.001). Short-term decreases in ESR or CRP levels at 6 weeks follow-up did not correlate with subsequent mass regression but decrease in ESR at 4 months and decrease in CRP at 4 and 8 months follow-up correlated with mass regression. Kaplan-Meier analysis showed no difference in remission rate between patients with normal or elevated baseline ESR or CRP (log-rank P=0.22/P=0.88) or between patients with or without (near-)normalization of ESR or CRP in first 6 weeks of treatment (log-rank P=0.12/P=0.32). CONCLUSIONS Patients with idiopathic RPF who have elevated acute-phase reactant levels are more symptomatic. Neither acute-phase reactant levels or their initial changes can be taken as a major predictor for treatment success.