Rituximab in immune thrombocytopenia: gender, age, and response as predictors of long-term response

Objectives: To evaluate the efficacy of a salvage treatment with rituximab (RTX) in adults with primary immune thrombocytopenia (ITP), in terms of short-term response and long-term response (LTR, i.e., probability to achieve and maintain response) and to identify biological and clinical predictors of response. Methods: We retrospectively evaluated the outcome of patients with primary ITP treated with standard dosage RTX (375 mg/m2 × 4) as salvage therapy in five Italian centers. One hundred and three patients, median age of 46 yr, were included. The median period of observation was 59 months. Results: Response (R) and complete response (CR) were documented in 57 (55%) and 37 (36%) patients, respectively. Patients younger than 40 yr had a higher probability to achieve CR (P = 0.025). Younger women (age < 40 yr) had a significantly higher probability to achieve R and CR (P = 0.039 and P = 0.009, respectively). The estimated LTR rate was 36% and 31% after 48 and 72 months, respectively; female sex (P = 0.033) and younger age (P = 0.021) were associated with better LTR. Younger women had the highest LTR rate (P = 0.006). Response duration was associated with the obtainment of CR after RTX (CR vs. partial response, P = 0.002). Conclusions: The effect of RTX salvage treatment appears higher in younger women, with LTR rate possibly approaching that of splenectomy.