Therapeutic Plateletpheresis for Thrombocytosis: Critical Analytic Reviews and Original Multicenter Experience

Primary thrombocytosis is associated with increased risk of thromboembolism and bleeding. Therapeutic plateletpheresis (TPP), capable of rapid, transient platelet (Plt) count reduction, is employed as an emergency intervention for symptomatic thrombocytosis while awaiting the therapeutic effect of medical cytoreductive therapy. Nonetheless, the effect of TPP on outcomes and optimal role for TPP remain poorly understood. Critical analytic review of highest-pertinence and -quality articles was performed with the goal of establishing current knowledge gaps to direct original case data collection. Retrospective review of TPP procedures at six United States sites over ten years was performed. Pre-TPP symptoms, medical cytoreduction, adverse events (AEs), and 30-day post-TPP outcomes were analyzed. Critical analytic review revealed no randomized controlled trial (RCT) or controlled trials (CT) of TPP versus first-line medical therapies, and insufficient information on symptoms, goals, criteria-based determination of course, and post-TPP outcomes. New data presented here details 45 adult patients receiving TPP for thrombocytosis. TPP was performed rarely (of n = 6 sites, median 4.5 TPP/10 years, range 4-20). The most frequent diagnosis was myeloproliferative neoplasm (MPN) (34, 75.6%). The most frequent symptoms were any neurologic symptoms (present pre-64.4% of TPPs). TPP goals were commonly Plt-related (n = 85, 94.4% total TPP) and were met in 72.9% of TPP with stated Plt-related goals. Often, (n = 11/50 single TPP or series) TPP was begun or continued despite resolution of the stated indication for TPP. AE occurred during 20% of TPP and were predominantly hypocalcemia related (17/18, 94.4%). Four patients died within 30 days post TPP, three of stroke, one of a non-stroke neurologic complication. All deaths were deemed unrelated to TPP. Critical analytic reviews revealed no RCTs or CTs, a paucity of data on TPP goals and prescribed courses, and significant variability in AE reporting. Little information on long-term outcomes is available. Without controlled evidence supporting clinical outcome benefit of TPP for symptomatic thrombocytosis, utilization is expected to be rare and guideline-informed, following careful consideration of known risk in the setting of unclear benefit.