Earlier Administration of Rituximab Allows Higher Rate of Long-Lasting Response in Adult Patients with Autoimmune Thrombocytopenia.

Background

Previous reports highlighted the potential short and mid-term therapeutic activity and safety of rituximab in adult patients with autoimmune thrombocytopenias.

Objectives

Primary objectives of this study were to evaluate the long-term efficacy and toxicity profile. Patients and methods From October 1999 to April 2005, 37 adults patients, median age 54 years, with active and symptomatic autoimmune thrombocytopenias (30 idiopathic thrombocytopenic purpura, 1 idiopathic thrombocytopenia and neutropenia, 4 thrombocytopenia and concomitant undifferentiated connective tissue disease, 2 thrombocytopenia and concomitant B-cell lymphoprolipherative disorders) that had relapsed or were refractory to at least a full course of steroid therapy received weekly infusions of rituximab 375 mg/m² for 4 weeks. The median interval from diagnosis to rituximab was 34 months (1–264 months) and the platelets median count was 11 x 10⁹/L. The following parameters of efficacy and toxicity were considered: rate of complete and partial response, time to initial and maximum response, relapse rate, relapse free survival, treatment free survival, short and long-term toxicity. The possible prognostic influence of some clinical and laboratory parameters on the patients outcome were also analyzed.

Results

Complete and partial response (platelets count ≥ 100 x 10⁹/L and ≥ 50 x 10⁹/L) were 20/37 (54%) and 7/37 (19%), respectively. In most of the patients the time to initial and maximum response was prompt, already before the second administration of rituximab. The median period of observation from treatment was 22 months (1–48 months). Nine out 27 responding patients relapsed; 18/37 patients (49%) remained relapse free and 20/37 (54%) did not necessitated further therapy. A shorter interval period from the time of diagnosis and rituximab administration (≤ vs > 36 months) was associated with a lower relapse free survival (p= 0.03). During the period of rituximab administration, 2 patients experienced short term toxicity with one case of serum sickness syndrome; no infectious or other significant long term toxic complications were documented..

Conclusion

Rituximab administration may allow to achieve long-lasting remission in nearly 50% of patients suffering from autoimmune thrombocytopenia with good toxic profile. The possibility to achieved long lasting response appeared related with an earlier timing of administration.