Primary Immune Thrombocytopenia and Thrombopoietin Receptor Agonists: Feasibilities of Treatment Discontinuation upon Achieving Stable Complete Platelet Response

Abstract

Aim. To assess the stability of clinical remission in patients with primary immune thrombocytopenia (ITP) after withdrawal of thrombopoietin receptor agonists (TPO-RAs). Materials & Methods. The study enrolled 456 patients with primary ITP who received second- and subsequent-line TPO-RA treatment. Complete platelet response (PR) was achieved in 338 patients, the therapy was discontinued in 116 of them. The present prospective clinical study started in 2014 and focused on the data of these 116 patients. Among them, there were 27 (23 %) men and 89 (77 %) women. By the time of TPO-RA therapy onset, the median age of the patients was 60 years (range 13–87 years), on ITP diagnosis date it was 52 years (range 1–80 years). Results. By the time of data analysis, 59 % of patients sustained PR after TPO-RA withdrawal. The median PR duration after TPO-RA withdrawal was 230 weeks. Romiplostim and eltrombopag recipients showed no significant differences in the survival rates without PR-loss after TPO-RA withdrawal. In the present study, the maximum PR duration achieved 9.5 years. The mid-term assessment of PR status was carried out in 3, 6, 12, 24, and 30 months after TPO-RA withdrawal and showed 99 %, 94 %, 83 %, 72 %, and 70 %, respectively. The number of previous therapy lines significantly affected the survival rates without PR-loss (p = 0.011). The age of patients, prior splenectomy, TPO-RA treatment duration, time to different PR levels on therapy, PR duration on TPO-RA therapy, and platelet count upon TPO-RA withdrawal showed no significant effect on this parameter. After PR-loss, TPO-RAs were administered again to 31 (27 %) patients. Repeated PR was achieved in 26 (84 %) of them. Conclusion. TPO-RA administration yields multi-year off-treatment remission in some patients with primary ITP. Upon therapy discontinuation, 59 % of patients with complete PR sustained PR for 3 months to 9.5 years. Stable PR after TPO-RA withdrawal significantly correlated with only one of the studied prognostic parameters, i.e., the number of previous therapy lines.