Impact of Leukapheresis and Time to Chemotherapy on Outcomes of Newly Diagnosed Patients (pts) with Acute Myeloid Leukemia (AML) Presenting with Hyperleukocytosis: An Analysis from a Large International Patient Cohort

Introduction: Hyperleukocytosis, defined as a white blood cell count (WBC) of >50 × 109/L or >100 × 109/L, is seen in newly diagnosed AML and often results in leukostasis, increased risk of complications, and potentially early death. Those pts often require urgent evaluation and therapy. Leukapheresis is also sometimes used despite limited evidence supporting its use. There is limited data regarding the impact of time (day/night) and day (weekday/weekend) of admission and time to initiation of IC on outcomes in pts with hyperleukocytosis. Methods: Data were collected from 12 centers in USA and Europe (EU). Eligible pts had newly diagnosed AML, presented with a WBC > 50 × 109/L, and received IC. Univariate and multivariable logistic regression models stratified by centers (EU vs. USA) estimated odds ratios for death during induction (30-day mortality) and achievement of composite complete response (CRc) defined as CR+CR with incomplete count recovery (CRi). Univariate and multivariate Cox proportional hazard models stratified by centers (EU vs. USA) estimated hazards ratios (HR) for overall survival (OS). We evaluated the impact of leukapheresis, day of presentation (weekend vs. weekday), time of presentation (nighttime = 6pm-6am vs. daytime=6am-6pm), and time to initiation of IC. Studied covariates included age, Eastern Cooperative Oncology group performance status (ECOG PS), cytogenetics and molecular abnormalities, WBC, hemoglobin, platelet count, bone marrow and blood blast percentage, and presence of clinical leukostasis, tumor lysis syndrome (TLS) or disseminated intravascular coagulation (DIC) at presentation. Results: Among 1050 pts with AML and hyperleukocytosis whose data were collected, 787 were reported to have received IC and were included in this analysis. Of 787 pts receiving IC, 16.6% (95%CI, 13.9-19.3%) died during the first 30 days of IC. Leukapheresis was used in 117 pts (15%) in 8 of the 12 centers. In univariate analyses, neither weekend nor nighttime presentation nor use of leukapheresis impacted odds of death in the first 30 days. In multivariate analysis, higher odds of death during first 30 days were associated with age ³ 55 years (OR 3.2, p=0.015), ECOG PS ³ 2 (OR 4.4, 0.004), WBC > 100 × 109/L (OR 6.0, p=0.01) and presence of leukostasis (OR 4.5, p=0.005) and TLS (HR, 3.2, p=0.049). However, neither initiation of IC beyond 48 hours of presentation (vs. less than 48 hours) or use of leukapheresis significantly affected the odds of