LAUSR

225 Background: Acute leukemias (AL) may present with variable clinical findings, from incidental discovery to respiratory distress or obtundation. However, patients may progress rapidly, requiring emergent treatments including leukophoresis, chemotherapy or radiation. There is little to no data supporting the use of radiation therapy in the setting of presumed lung infiltration. We present the first known case series on the treatment of presumed leukemic lung infiltration with empiric radiation therapy (eRT). Methods: Eleven patients with AL from 2008 – 2018 were identified who were treated with eRT at our center. All patients were on empiric antibiotics, and all were noted to have at least one chest plain film with suspicious infiltrates. The median age was 66 years old (29-77), and five of eleven patients were febrile at the start of radiation. One patient had been intubated prior to radiation delivery. Three of seven patients underwent leukophoresis and six of ten patients received any chemotherapy prior to eRT. Results: The median treatment regimen was 450cGy (range 50 – 1050) in 3 fractions (1 – 7). The median white blood cell (WBC) count prior to radiation therapy was 119.0 x 103 /μL (highest recorded, 1.9 – 317.6), with median blast percentage on manual differential, 88% (3 – 98). All eleven patients had a large reduction in WBC count within the first day of eRT, with median response 48.2% decrease in WBC count (31.7 –99.8; average 57.3%). Ten of ten patients reported subjective improvement in breathing. Conclusions: Empiric radiation therapy is a safe and effective means for rapidly decreasing leukocyte counts and for symptomatic palliation in patients with AL and radiographic chest infiltrates.