Abstracts Clinical Lymphoma, Myeloma & Leukemia September 2023 S276 Introduction: Central nervous system (CNS) involvement in acute myeloid leukemia (AML) has been understudied due to the lack of guidelines for screening and treating in this population. In this study, we evaluated the treatments and outcomes of CNS AML patients at two large academic institutions. Methods: Patients with CNS AML were retrospectively identified at Mount Sinai Hospital and the University of Kansas Medical Center. CNS AML was defined as the presence of leukemic blasts in the cerebral spinal fluid (CSF) or atypical immature myeloid cells in the CSF with either suspicious imaging findings and/or neurologic symptoms. Descriptive statistics were employed, and the Kaplan-Meier method was used for survival analysis. Results: A total of 52 adult patients were identified. Features associated with CNS AML included monocytic differentiation (40%), elevated LDH (67%), white blood cells >100K (37%), and FLT3 mutation (46%). Neurologic symptoms were reported in 69% of patients, with headache as the most common (33%), followed by vision changes (25%) and radicular pain (10%). Ninety percent of patients received at least one dose of intrathecal (IT) methotrexate, 71% at least one dose of IT cytarabine, and 65% at least one dose of both. The median number of IT doses received was 4 (range 0-31). Eighty-four percent of patients achieved CSF clearance, with a median number of IT doses required for clearance of 1 (range 1-9). Of these patients, 21% had a CSF relapse with 67% of those with CSF relapse having concurrent bone marrow relapse. Of the 36 patients with baseline neurologic symptoms, 69% had improvement in symptoms post-IT therapy. The median overall survival was 9.3 months and 3.5 months for patients with CNS involvement diagnosed before/during induction and after induction, respectively. Discussion: In this study, IT therapy was shown to be rapidly effective in clearing CSF blasts and improving neurologic symptoms in most patients. Few patients experienced CSF relapse which typically occurred with concomitant bone marrow relapse. Prospective trials and larger multi-institutional collaborations are needed to inform better the optimal surveillance and treatment of CNS involvement in AML. Keywords: AML, central nervous system, intrathecal therapy, neurologic symptoms AML-197 Clinical Outcomes and Treatment Patterns in Adult Patients With FMS‑Like Tyrosine Kinase 3 Internal Tandem Duplication Positive Acute Myeloid Leukemia Undergoing Allogeneic Hemopoietic Cell Transplantation in the US and Canada: CIBMTR® (Center for International Blood and Marrow Transplant Research Analysis) Linda J. Burns MD1, Bhavik J. Pandya PharmD2, Karen Chen MS2, Tao Wang PhD1, Bin Xie PhD2, Maelys Touya PharmD2, James Spalding PharmD, MSc, MBA2, Alana Block PharmD, BCOP2, Gaston Kuperman MD2, Christopher Young PhD2, Lori Muffly MD3 1CIBMTR® (Center for International Blood and Marrow Transplant Research), Milwaukee, WI, USA. 2Astellas Pharma US, Northbrook, IL, USA. 3Stanford University, Stanford, CA, USA Context: Allogeneic hemopoietic cell transplantation (allo-HCT) is commonly used to treat patients with acute myeloid leukemia (AML) with internal tandem duplication of the FMS-like tyrosine kinase 3 gene (FLT3-ITDmut+). However, key characteristics and clinical outcomes are not fully understood. Objective: Determine the impact of patient, disease, and transplantation characteristics on outcomes, trends in maintenance therapy, and causes of death for patients ≥18 years with FLT3-ITDmut+ AML undergoing first alloHCT. Design: Observational cohort study of recipients of human leukocyte antigen identical sibling, haploidentical, 8/8 or 7/8 unrelated, or cord blood donor allo-HCT in the USA and Canada between January 1, 2014, and December 31, 2019, reported in the CIBMTR® database. Patients enrolled in NCT02997202 (postallo-HCT gilteritinib maintenance) were excluded. Patients: 3 147 patients with disease status at allo-HCT: first complete remission (CR1; n=2389); second or greater complete remission (≥CR2; n=340); and relapsed/refractory (R/R; n=418). Main Outcomes: Overall survival (OS) and leukemia free survival (LFS) were the main outcomes. Other outcomes included relapse and nonrelapse mortality (NRM). Cox proportional hazards models were used for multivariable analyses. Results: Median (range) follow-up for all patients was 43 (3–90) months. Characteristics were similar for all cohorts. Disease status (≥CR2 vs CR1) significantly impacted OS (hazard ratio [HR] 1.44; 95% confidence interval [CI] 1.20–1.73; P=0.0001]), LFS (HR 1.98; 95% CI 1.52–2.59; P<0.0001), and relapse (HR 2.50; 95% CI 1.84–3.40; P<0.0001). Outcomes were worse for R/R than ≥CR2 disease. NRM was not significantly associated with advanced disease. Higher HCT-comorbidity index scores, longer time from diagnosis to allo-HCT, and advanced age were associated with inferior OS and/or LFS; higher HCTcomorbidity index scores were associated with increased likelihoods of relapse and NRM. Maintenance therapy usage increased from 2014 (11% [52/467]) to 2019 (47% [247/531]), primarily due to increased FLT3 inhibitor use (2014: 8% [37/467]; 2019: 40% [210/531]). Most deaths were from AML (60% [867/1453]). Conclusions: More advanced disease at time of allo-HCT was associated with poorer outcomes in patients with FLT3-ITDmut+ AML. Future research should focus on timing of HCT and impact of maintenance therapy to prevent post-HCT AML-related deaths. Keywords: AML, allogeneic hemopoietic cell transplantation, FLT3 inhibitor, overall survival, leukemia free survival AML-204 Thrombocytopenia Mimicking an Unusual Myelotoxicity Post Standard Cytotoxic Chemotherapy in Ovarian Cancer Lina El Murr MD, Charif Tarhini MD, Georges El Hachem MD Saint George Hospital University Medical Center, Beirut, Lebanon
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