Long Term Follow up of Patients with Immune Thrombocytopenia Receiving Rituximab

Rituximab has been used in the management of chronic immune thrombocytopenia (ITP) with promising results. The risk of losing response, however, is yet to be determined with long term follow up.

We retrospectively analyzed 32 consecutive patients (20 females, 12 males) with ITP (including 6 patients with secondary ITP) treated with rituximab in two tertiary care hospitals in Oman between May 2006 and May 2011. Response criteria were based on the International Consensus report (Rodeghiero F et al. Blood 2009).

The median age at diagnosis was 25 years (range, 4 – 58). Clinical presentation ranged from mild echymosis to more severe central nervous system bleeding. Patients received a median of one line of therapy before rituximab (range, 1–4), including 3 patients who failed splenectomy. Patients received intravenous rituximab using 375 mg/m² once weekly for 4 weeks. The median time from diagnosis to receiving rituximab was 21 months (range, 1– 177). Only one patient was positive for Hepatitis C virus, but no hepatitis B or HIV positive in this cohort. Anti nuclear antibody was positive in 34% (10/29) of patients. The median hemoglobin and platelet counts at diagnosis were 12 g/dl (range, 5–16) and 11×10⁹/L (range, 1–60) respectively. The median follow up time after rituximab was 26 months (95% confidence interval: 11–40). The overall cumulative response rate was 59% (partial response of 15% and complete response of 44%). The median time to respond was 30 days (Standard error [SE] 49) with a response rate of 44% at 4 weeks (95% Confidence interval: 29–62%). The multivariable Cox model analysis (variables include: age at diagnosis, gender, number of previous therapies and primary vs. secondary) revealed none of the variables included to be statistically significant. The cumulative rate of loss of response was 32% (6/19) with a median time to lose response of 54 months (SE, 0.03). In patients who lost response, the median time to lose response was 17 months (SE, 14). Of the 6 patients who lost response, 4 received a second course of rituximab and all 4 achieved a full response. No major side effects to rituximab were reported during the follow up.

Rituximab is an effective and a well tolerated second line therapy for ITP. The response to rituximab can be maintained for a long duration with a high rate of response after retreatment. None of the pretreatment variables studied carried a significant predictive value for response. The study was limited by the small sample size and further larger prospective studies are recommended.

Off Label Use: Rituximab was used in our study as a second line for the management of chronic immune thrombocytopenia.