Rituximab in the management of retroperitoneal fibrosis: A single tertiary rheumatology care center experience.

Aim: To investigate the clinical and radiological outcomes and glucocorticoid-sparing effect of rituximab therapy in 13 patients with retroperitoneal fibrosis (RPF).

Methods: We analyzed the data of both glucocorticoid-naive and glucocorticoid-resistant RPF patients who were treated with rituximab. Demographic features, positron emission tomography computed tomography (PET-CT) findings, and clinical and histopathologic outcomes were collected retrospectively.

Results: We evaluated the data of 13 RPF patients (8M/5F). The median follow-up duration was 28 months (interquartile range [IQR] 24.5-55.5 months) and median age at the time of diagnosis was 50.8 years (IQR 46.5-54.5 years). PET-CT scans showed that following the rituximab therapy, the craniocaudal diameter of the RPF mass reduced from 74 mm (IQR 50.5-130 mm) to 52 mm (IQR 35-77 mm; p = .06), and periaortic thickness of the RPF mass reduced from 14 mm (5.5-21.9 mm) to 7 mm (4.5-11 mm; p = .12). The maximum standardized uptake value (based on body weight) of the RPF mass decreased from 5.8 (4.3-9.7) to 3.1 (2.8-5.3) after the therapy (p = .03). The number of patients with hydronephrosis reduced from 11 to 6 following rituximab therapy (p = .04). Before rituximab, nine patients received a median dose of 10 mg (IQR 0-27.5 mg) prednisolone per day. After the rituximab treatment, we discontinued prednisolone treatment for four out of nine patients and reduced the daily dose for the remaining patients. At the time of the final evaluation of the patients, the median prescribed prednisolone dose was 5 mg/day (IQR 2.5-7.5 mg/day; p = .01).

Conclusion: Our study shows that rituximab may be a favorable treatment option for glucocorticoid-refractory RPF patients with high disease activity on PET-CT scans.