298. RITUXIMAB FOR DIFFICULT-TO-TREAT CHRONIC PARIAORTITIS: A CASE-SERIES OF 20 PATIENTS

Background: Chronic periaortitis (CP) includes a spectrum of rare diseases characterized by a fibro- inflammatory tissue enveloping abdominal aorta and iliac arteries, which extends into the retro- peritoneum to encase adjacent structures. It has recently been reported that 50% of CP cases belong to the group of IgG4-related disease (IgG4-RD). Glucocorticoids are the best option to induce remission, but 30-50% of patients relapse after steroid withdrawal or do not tolerate standard steroids doses. Rituximab was successfully used in IgG4-RD. We assessed the efficacy and safety of rituximab in patients with difficult-to-treat CP who did not have evidence of an IgG4-related form. Methods: We enrolled 20 patients affected by CP with active disease documented by CT-scan and positron emission tomography (PET)/CT. None of the patients had evidence of IgG4-RD. Sixteen patients were refractory to previous treatments (consisting of glucocorticoids and conventional immunosuppressants) while the remaining 4 were newly diagnosed and had contraindications to standard-dose of steroids. Rituximab was given at dose of 1g repeated after 15 days, used monotherapy in 4 patients, while in the remaining 16 low-dose prednisone (initial dose 425 mg/day) was added. Nine patients were treated with low-dose Rituximab as maintenance therapy. Results: The median follow-up of the whole cohort was 18 months (ICQ 11.50-26.75). One patient was lost to follow-up at month 4. After 6 months of therapy 50% of patients achieved remission based on disappearance of clinical symptoms, resolution of hydronephrosis and normalization of inflammatory markers; after 12 and 18 months, 81% and 83% of patients were in remission respectively. During the follow- up 2 patients relapsed 50 and 46 months after rituximab therapy respectively, and responded promptly to re-treatment. Nine patients repeated standard low- dose rituximab every 6 months for mainten- ance. Treatment-related toxicity was negligible and none of the patients had to stop treatment. No significant hematologic toxicity nor serious infections occurred during the follow-up. Conclusion: Rituximab appears to be a valid and safe therapeutic option also for CP patients with no evidence of IgG4-RD who had refractory disease or contraindications to standard glucocorticoid therapy.