Outcomes of rituximab as treatment for immune thrombocytopenic purpura in patients who have failed steroids or IVIG: A retrospective study in a community practice.

Abstract

e23256 Background: Immune thrombocytopenic purpura (ITP) is a challenging disorder with multiple treatment options. The 2019 American Society of Hematology guidelines outline treatment recommendations for ITP which include intravenous immunoglobulin (IVIG) and steroids as first-line, with Thrombopoietin receptor agonists (TPO-RAs) and Rituximab as second-line agents. They favor TPO-RAs over Rituximab but suggest that the choice should be individualized. In this study, we explore the rate and duration of response to Rituximab as a second-line agent for ITP. We also analyze relapse rates and response to sequential TPO-RAs. Methods: A retrospective study of patients with ITP managed in a community practice from 2018 to 2022. The practice’s electronic medical records were searched for the keywords “ITP” and “Rituximab”. 87 patients fit the search terms. We included patients above age 18 treated with Rituximab for ITP after failing steroids or IVIG. We excluded duplicates, incomplete medical records, patients given Rituximab for reasons other than ITP, patients treated with medications other than steroids or IVIG prior to Rituximab, and patients given less than 4 doses of Rituximab. 60 out of 87 patients were eligible. The primary outcome was response to Rituximab defined as platelets above 30,000 per microliter of blood after 12 weeks of its initiation. Secondary outcomes include relapse rate, duration of response, and subsequent response to TPO-RAs. Secondary outcomes were determined by chart-reviewing physician documentation. Results: SAS 9.4 (SAS/STAT Inst., Carry NC) was used for all data. Categorical variables were quoted as absolute numbers and relative frequencies. A test result was considered statistically significant if p < 0.05. For categorical variables, likelihood ratio chi-square, and Fisher’s exact tests were conducted for 2*2 and r*c contingency tables to test associations. 96.7% of eligible patients responded to Rituximab (P < 0.0001), however 46.7% relapsed. 42.9% of relapses happened in less than 1 year, 14.3% in 1 year, 21.4% in 2 years, 7.1% in 3 years, 10.7% in 4 years, and 3.6% in 5 or more years (P = 0.0043). The response rate to TPO-RAs after Rituximab failure was 88%. No significant toxicity from Rituximab was noted beyond previously reported minor side effects, and there was no treatment-related death. Conclusions: The response rate to Rituximab was 96.7% (P < 0.0001) which was sustained in 53.3% of patients. Most relapsed patients responded well to TPO-RAs. These numbers are very comparable to previously reported response to Rituximab. Therefore, we believe that the strategy of using Rituximab as second-line and reserving TPO-RAs for non-responders is clinically-effective and certainly cost-effective given the fact that Rituximab is administered over four weeks as compared to the often lifetime treatment with TPO-RAs.