Use of rituximab in idiopathic retroperitoneal fibrosis

BACKGROUND: Retroperitoneal fibrosis (RPF) is characterized by the proliferation of fibrous tissue in the retroperitoneum. The majority of RPF cases are due to idiopathic or IgG4-related disease. Recent studies on IgG4-related disease have shown rituximab to be an effective treatment. The current first-line treatment for idiopathic RPF (iRPF) is glucocorticoid therapy. Relapse rates vary widely in the literature, and DMARDs remain poorly studied. We sought to evaluate the efficacy of rituximab in idiopathic RPF by quantifying changes in iRPF diameter on imaging pre- and post-rituximab therapy and response by lab parameters in 10 iRPF patients. METHODS: We selected 10 patients diagnosed with iRPF and previously treated with rituximab (1000 mg) in two doses approximately 2 weeks apart. Pre- and post-therapy contrast enhanced cross-sectional abdomen and pelvis imaging were compared. In all patients, the thickest portion of the peri-aortic disease was measured in the axial and coronal planes. The presence of acute or long standing back pressure related renal findings were documented. Details of clinical visits including patient demographics and laboratory evaluations were collected pre- and post-therapy. Statistical analysis was performed using a Wilcoxon signed rank test. RESULTS: The RPF diameter around the aorta before and after therapy decreased from a mean of 15.9 ± 4.9 mm to 10.6 ± 6.1 mm, respectively (p < 0.01). The craniocaudal iRPF mean length decreased from 108.6 mm ± 40.4 mm to 90.6 mm ± 45.9 mm (p = 0.02). CONCLUSION: A comparison of pre and post-rituximab imaging studies revealed a statistically significant decrease in iRPF diameter following treatment with rituximab.