Thrombocytapheresis for Extreme Thrombocytosis: A 20‐Year Single‐Center Experience With Acute and Chronic Use in Myeloproliferative Neoplasms

ABSTRACT Thrombocytapheresis is an established adjunctive therapy for rapid platelet cytoreduction in patients with extreme thrombocytosis, particularly in myeloproliferative neoplasms (MPNs), where it is typically used alongside cytoreductive pharmacotherapy. Real‐world longitudinal data describing utilization, effectiveness, and safety remain limited. The aim of this study was to evaluate or characterize the indications, utilization patterns, hematologic responses, and safety outcomes of thrombocytapheresis over a 20‐year period at a single institution and illustrate key clinical applications through two illustrative cases. We conducted a retrospective 20‐year institutional review of thrombocytapheresis, highlighting two illustrative cases. Cases were identified using EPIC SlicerDicer. Patient demographics, indications, laboratory responses, adverse events, access complications, electrolyte abnormalities, and short‐term outcomes were extracted and analyzed. Pre‐ and post‐platelet count changes were assessed using paired Wilcoxon testing, with exploratory analyses of other blood cells and descriptive evaluation of safety outcomes. After applying exclusion criteria, 9 patients undergoing 38 thrombocytapheresis procedures were analyzed, with one patient accounting for nearly half of all procedures. Most procedures were performed for MPN‐related thrombocytosis. In the broader cohort, platelet counts decreased significantly after the first procedure (median 1511 to 666 × 10 9 /L; p = 0.008), corresponding to a mean reduction of 45% with no significant changes in red cell and white cell counts. Adverse events were uncommon and primarily related to citrate‐associated hypocalcemia or vascular access rather than to circuit‐related complications. We also report two cases describing thrombocytapheresis use in patients with extreme thrombocytosis (> 2.9 million/μL) in distinct myeloid neoplasms. The first patient was diagnosed with polycythemia vera evolving from essential thrombocythemia and demonstrated relative refractoriness and platelet count rebound despite cytoreductive therapy, followed by rapid platelet decline but poor clinical outcome. The second is a case of chronic myeloid leukemia refractory to multiple tyrosine kinase inhibitors (including dasatinib and nilotinib). The patient demonstrated sustained responsiveness to serial thrombocytapheresis over 2 years. In this cohort, thrombocytapheresis was effective for rapid platelet reduction and demonstrated an acceptable safety profile. Clinical outcomes are largely dictated by underlying disease severity and concurrent cytoreductive therapy, rather than procedural response alone. In selected patients, thrombocytapheresis may serve as an effective bridging therapy while awaiting definitive treatment.