Abstract

e18509 Background: Hyperleukocytosis (white blood cell (WBC) count greater than 100x10 9 ), which may lead to the clinical entity of leukostasis, is a hematologic emergency present at diagnosis in 18% of patients with acute myeloid leukemia (AML). There is controversy regarding the appropriate cytoreductive strategy, which may include cytoreductive chemotherapy, hydroxyurea, and/or leukapheresis. The American society for apheresis (ASFA) released guidelines in 2023 making leukapheresis a Category III recommendation, however significant heterogeneity and methodologic flaws exist in the evidence used to make these recommendations. Methods: Retrospective analysis of 58 patients at Massey Comprehensive Cancer Center between 2017 and 2023 who received either hydroxyurea alone (n=35) or both hydroxyurea and leukapheresis (n=23) for hyperleukocytosis at time of presentation for AML diagnosis was performed. Baseline characteristics including age, sex, Charlson Comorbidity Index (CCI), European LeukemiaNet (ELN) risk stratification, and WBC count prior to cytoreduction were collected. Comparisons of complete remission rates (CR/CRi), 30- and 60-day mortality, median overall survival (OS), and rates of therapy-induced tumor lysis syndrome (TLS) and disseminated intravascular coagulation (DIC) were analyzed using Kaplan-Meier, Fisher’s exact, Mann-Whitney tests, respectively on a propensity score matched cohort to account for differing initial WBC counts between the treatment groups. Results: PSM was used to match presenting WBC counts between the two cohorts. Other baseline characteristics including median age (65y v. 60y), median CCI (5 v. 4), ELN adverse risk rate (31.53% v. 26.1%) did not differ after PSM. No significant difference was found between the hydroxyurea group compared to the hydroxyurea and leukapheresis group, respectively, when analyzing for rate of CR/CRi (36.5% v. 43.5%), 30-day mortality (10.5% v. 17.3%), 60-day mortality (10.5% v. 34.8%), median OS (7.77 mo. v. 8.07 mo.), or rates of DIC (10.5% vs. 8.7%) and therapy induced TLS (0% v. 0%). Conclusions: Patients who received hydroxyurea alone had similar outcomes when compared to the combined treatment group with respect to median OS, CR/CRi, and mortality rates. These results are notable given that leukapheresis is not available at many medical centers and is a resource-heavy procedure, and especially so in light of new ASFA guideline changes. However, these results reflect the laboratory entity of hyperleukocytosis rather than the clinical entity of leukostasis. Further work is ongoing to assess impact of cytoreductive strategies in leukostasis in AML, and among different cytogenetic and molecular subtypes. Decisions for leukapheresis or other cytoreductive strategies should be made on a case-by-case decision at an experienced center when possible.