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Abstract 4319 Background: CBs are highly variable at diagnosis and during the course of IT in AML patients. Assessing response to IT carries a huge implication on the prognosis of individual patient with AML. Our study investigates whether late clearance of CBs during IT using standard cytarabine + anthracycline regimen is associated with refractory phenotype. Methods: We retrospectively reviewed the chart of 83 AML patients (43 males, 40 females, mean age 61.7) who received standard cytarabine and anthracycline regimen during induction between January, 2000-January, 2011 at William Beaumont Health System. Data collected include complete blood count with blast count during course of induction, and bone marrow response. AML is considered refractory if morphological evaluation, flow cytometry or cytogenetic study was positive in the first bone marrow post induction. Response to IT was assessed according to Cancer and Leukemia Group B (CALGB) criteria as complete remission versus residual leukemia or treatment failure (failing to achieve complete remission). Results: We noted that 57 of 83 patients (68.7%) showed CBs at the time of diagnosis. During the IT, CBs clearance occurred within 7 days (early clearance) in 38 of these 57 patients. The remaining 19 patients had CBs persistent more than 7 days (delayed clearance). The frequency of bone marrow residual disease at count recovery post IT was significant higher in patients with late clearance and those with early clearance (84% vs 42%, p=0.0015). Further analysis of data showed the frequency of bone marrow residual disease was not significantly different between patients with no CBs at the diagnosis and those with early clearance of CBs (38% vs 42%, p=0.8). Conclusion: Adult AML patients with persistent CBs >7 days during IT with standard induction cytarabine and anthracycline regimen are more likely to have induction failure. CBs clearance can be used as an early assessment of response to the IT. Disclosures: No relevant conflicts of interest to declare.

Abstract 3148 Background: VTEs are common complications in association with IT which may cause additional morbidity and mortality in AML patients. However, treating patients with AML is challenging because of the cytopenias due to chemotherapy and the high risk for bleeding during IT. This study investigates frequency, risk factors, and safety of using anticoagulation (AC) therapy for VTEs during IT. Method: We retrospectively reviewed the charts of AML patients who received IT between January, 2000-January, 2011 at William Beaumont Health Systems. Exclusion criteria included a documented personal history of inherited thrombophilia. Data retrieved included the following: patient characteristics, leukemia subtype, cytogenetic risk, location of the VTEs, FLT3 mutations, IT regimen used (cytarabine and anthracycline regimens or hypomethylating agents), AC therapy, bleeding complications, mortality related to AC therapy. All patients who received AC were initially treated with regular intravenous unfractionated heparin or subcutaneous low molecular weight heparin. Patients were subsequently started on oral warfarin during the first 10 days of the initial treatment with a targeted INR of 2.0–3.0. Results: We found 48 of 363 (13.2%) AML patients developed VTEs during IT. Of those patients, 56.3 % were female. The VTEs occurred most frequently in upper extremities (58%) and were catheter-related. Other locations for VTEs included lower extremities (21%), pulmonary embolism (15%), and mesenteric or portal veins (6%). We note that 41 patients (87%) received AC therapy. Of these, three patients (7.3%) had bleeding complications and no AC therapy-related deaths were observed. When the three cytogenetic risk groups were compared, there was no difference in the incidence of VTEs (good vs intermediate vs poor). Patients with FLT 3 mutations, however, had a significant higher incidence of VTEs when compared to patients without FLT3 mutations (55.3% vs 12% p Conclusions: We found that 13% of AML patients developed VTEs during IT, most commonly in upper extremities and were catheter-related. The risk for VTEs was markedly increased in patients with FLT3 mutations. Furthermore, using a cytarabine + anthracycline regimens carried a higher risk for VTEs when compared to regimens using a hypomethylating agents. Finally, using AC therapy during IT is relatively safe and is associated with low risk of bleeding complications. Disclosures: No relevant conflicts of interest to declare.