Risk Profile, Efficacy and Safety of Rituximab in Patients with Relapsed or Refractory Idiopathic Thrombocytopenic Purpura in a Minority Cohort with Long Term Follow up

Background: Idiopathic Thrombocytopenic Purpura (ITP) is a common hematological disorder. We sort to characterize the risk profiles and efficacy of rituximab in relapsed or refractory ITP in a largely minority cohort.

Methods: 23 patients (pts) with relapsed or refractory ITP treated with Rituximab were identified and studied as a retrospective cohort. Demographics, presentation, dosage schedule, tolerability and response were analyzed. Continuous data were analyzed via Student’s T test, categorical data via Fisher’s exact test and time to progression data was analyzed via Kaplan Meier life table analysis and log rank test.

Results: Of the 23 patients, 20 female (87%), 3 male (13%). median age at diagnosis was 45 yr (range 20–66).9 pt were African American (39%), 9 Hispanics (39%), 4 Asian (17.4%), 1 Caucasian(4.3%), 9 (39.6%) had more than one co morbidities, 17 (73.8%) had received 3 or more treatment regimens. All pt received steroids, 18 (78.3%) received IVIg, 13 (56.6%) Anti D immunoglobulin, 5 (21.7%) Vincristine, 3 (13%) Azathioprine, 2(8.7%) Cyclophosamide, 6 (26.1%) underwent a Splenectomy before Rituximab therapy. The median time from diagnosis to rituximab therapy was 15 months (range 1 to 269). Median platelet count before rituximab therapy was 11 (range 3 to 200).

Rituximab was administered at the dose of 375mg/m2 IV once a week for 4 weeks. The response rate was 47.8%. Response was defined as Complete response, platelet count of > 100 × 10⁹/L, Partial response >50 × 10⁹/L. 9 pt (39%) achieved complete response, 2 pt (8.7%) achieved partial response. 12 pt (52.2%) did not respond. Median time to response was 13.5 days (range 1–30). There was no statistically significant difference in the response when compared by gender (p=0.64), race (p= 0.398), prior splenectomy (p=0.64), prior anti D immunoglobulin (p=1.0), prior Vincristine (p=1.0), prior cyclophosamide (p=.45), prior azathioprine (p=1.0). Four pt (17.4%) had a serious adverse reaction to rituximab. One pt had diffuse hives after infusion, three pt developed diffuse pancytopenia, two pts had gram negative sepsis and died. The median follow up after rituximab therapy was 18 months (range 1–60). The median time to relapse was 7 months (range of 1 to 59). There was no statistically significant difference in time to relapse among gender (p=0.19), race (p= 0.45), Prior splenectomy (p=0.86), prior Anti D immunoglobulin (p=0.32), prior vincristine (p=0.75).

Conclusion: In this primarily minority based cohort the response rate to Rituximab (48% vs. 62%) and duration of response (7 months vs. 10.5 months) was lower than other published data but the rate of serious adverse events (17% vs. 7%) was higher. Rituximab must be used cautiously in this sub group of patients. There is need for a randomized controlled clinical trail to assess the efficacy of Rituximab in this population and further studies are warranted in minority populations.