SAT0534 RITUXIMAB FOR REFRACTORY IDIOPATHIC RETROPERITONEAL FIBROSIS: A SINGLE TERTIARY CENTER EXPERIENCE
Authors: M. Oztas, E. Cerme, S. Ugurlu
Journal: Annals of the Rheumatic Diseases (2020)

Background: Idiopathic retroperitoneal fibrosis (RPF) is a progressive disorder of the retroperitoneum which is often idiopathic. Although prednisolone is the mainstay approach to treating RPF, the remission rates range between 75% to 95% (1-2). Objectives: Here, we report the outcomes and steroid-sparing effect of Rituximab (Rtx) therapy in 14 patients with RPF. Methods: This retrospective study was conducted at a tertiary rheumatology center. Patients were diagnosed with RPF and had at least a course of 0.5-1 mg/kg prednisolone treatment previously. These patients were switched to Rtx due to inadequate response or side effects while on prednisone, tamoxifen, azathioprine or cyclophosphamide therapy. Patients were treated with Rtx in order to be included in this study. Involvement and activation of RPF was shown via PET-CT either before or at least 6 months after the therapy. Daily prednisolone dose was noted before rituximab initiation and 6 months after the therapy. All of the patients reported, except two, were followed for at least 6 months after the Rtx treatment. The final disease status of the three patients were not included in the study. Results: Fourteen patients (7F) received at least 2 cycles (1 gr for each) of Rtx. The age of diagnosis was 54.3 ± 11.0 years, follow-up duration was 46.0 ± 37.2 months. The previous treatments, number of the cycles of Rtx and final disease status were shown in the Table. The Control PET-CT revealed metabolic and radiologic remission in 3 patients. In 6 patients, the disease remained stable. In 2 patients there was disease progression hence they were treated with the second course of Rtx. One of the two patients had the progression two years after the first cycle but then, was lost to follow-up. The mean prednisolone dose decreased from 15.5 ± 12.4 mg to 2.2 ± 2.2 mg/day after 6 months of Rtx initiation. Final prednisolone dose was 2.6 ± 5.5 mg/day (Figure). Rtx treatment was ceased in 6 patients with sustained remission. Conclusion: The present study shows that Rtx could be a therapeutic option after gluocorticoid or DMARD failure. The steroid sparing effect of Rtx is essential and further prospective studies are needed to assess the Rtx efficacy more objectively in RPF treatment. Table. Characteristics and final disease status of the patients Number Age of Rituximab Initiation Sex Previous Treatments Number of Rituximab Cycle(s) Final Pet-CT 1 49 M Pred, Mtx 1 Stable disease 2 54 M Pred,Mtx 1 Stable disease 3 46 F Pred,Aza,Tmx,Mmf 2 Progression 4 40 M Pred,Aza,Mtx 4 Remission 5 63 F Pred,Tmx 10 Stable disease 6 47 F Pred,Mtx 2 Stable disease 7 30 F Pred 1 Stable disease 8 52 M Pred,Aza 2 Progression 9 54 M Pred 1 N/A 10 59 M Pred,Aza,Mtx 1 N/A 11 30 F Pred, Mtx 6 Remission 12 40 F Pred,Aza,Tmx;Cyc 3 Stable disease 13 50 M Pred 2 N/A 14 45 F Pred,Aza 3 Remission Pred:Prednisolone, Aza:Azathioprine, Tmx:Tamoxifen,Mtx:Methotrexate,Cyc:cyclophosphamide References: [1]Vaglio A, Palmisano A, Alberici F, Maggiore U, Ferretti S, Cobelli R, Ferrozzi F, Corradi D, Salvarani C, Buzio C: Prednisone versus ta- moxifen in patients with idiopathic retroperitoneal fibrosis: an open-label randomised controlled trial. Lancet 378: 338–346, 2011 [2]van Bommel EF, Siemes C, Hak LE, van der Veer SJ, Hendriksz TR: Long-term renal and patient outcome in idiopathic retroperito- neal fibrosis treated with prednisone. Am J Kidney Dis 49: 615–625, 2007 Disclosure of Interests: None declared