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.