Leukapheresis (WBC Depletion) Treatment for Patients with Acute Leukemia and Blast Crisis Can Enable a High Percentage of Patients to Undergo Induction Chemotherapy
Authors: Hofmann Jan C. , Kiprov Dobri D 
Published: October 2019

Abstract
Abstract 4281

Introduction:
Several retrospective, cohort studies have demonstrated that leukapheresis (WBC depletion) treatment in patients (pts) with acute leukemia and concurrent hyperleukocytosis and blast crisis decreases short-term mortality rate, but does not increase overall survival. However, pts selected in these studies for leukapheresis treatment are often sicker and have a higher underlying mortality rate (than pts who do not receive such treatment). No randomized controlled trials assessing the efficacy of leukapheresis in this subset of pts with acute leukemia have been performed.

Methods and Clinical Presentation:
Between January, 2006 and June, 2010, Apheresis Care Group (ACG) treated 1,636 pts performing 13,587 therapeutic apheresis treatments (txs). Of this patient cohort, 126 (7.7%) pts had acute leukemia with clinical and/or laboratory evidence of blast crisis and received leukapheresis treatment. 77 pts had acute myelogenous leukemia (AML) and received 174 leukapheresis txs; 49 pts had acute lymphoblastic leukemia (ALL) and received 158 txs. AML pts presented with median WBC 204 × 109/L (range 66–418 × 109/L) and 87% pts had blast crisis (defined as blast percent >75% or blast count >100 × 109/L). Median age was 54 years (6.5–85 years); 61% pts were male. Of CNS or pulmonary symptoms (sxs) of leukostasis (CNS sxs defined as: headache, lethargy, confusion, or visual abnormalities; pulmonary sxs defined as: shortness of breath, hypoxia, or chest x-ray infiltrates without evidence of pneumonia), 13% pts had no sxs, 52% pts had 1 sx, and 35% pts had 2 sxs. ALL pts presented with median WBC 338 × 109/L (104–736 × 109/L) and 82% pts had blast crisis. Median age was 22 years (4–80 years); 64% pts were male. Of sxs of leukostasis, 25% pts had no sxs, 63% pts had 1 sx, and 12% pts had 2 sxs.

Treatment:
All pts received a course of leukapheresis (Lp) with the following objectives: 1) decreasing the risk of thrombotic and hemorrhagic complications related to leukostasis, and 2) stabilizing pts for induction chemotherapy. WBC treatment goals were defined as: WBC count (ct) <55 × 109/L for AML pts, and WBC ct <80 × 109/L for ALL pts. AML pts received a median of 2 Lp txs (range 1–5 txs); ALL pts underwent a median of 2 Lp txs (1–7 txs).

Results:
Outcomes were evaluated by the percentage of pts who: 1) reached the WBC treatment goal and, 2) received induction chemotherapy. “Improved” outcome was defined as pts who reached their WBC treatment goal during leukapheresis therapy; “stabilized” was defined as pts who achieved >50% reduction in WBC ct, but did not reach their WBC goal; and “unchanged” was defined as pts who achieved neither. In the AML cohort, 76% pts improved, 23% pts stabilized, and 1% pts were unchanged. In the ALL cohort, 63% pts improved, 34% pts stabilized, and 3% pts were unchanged. For AML pts, the median final WBC ct was 53 × 109/L (range 17–133 × 109/L) and 92% pts received induction chemotherapy. For ALL pts, the median final WBC ct was 76 × 109/L (range 30–294 × 109/L) and 98% pts received induction chemotherapy. 7 (9%) AML pts and 1 (1%) ALL pt expired within 1–4 days after completing course of leukapheresis. Of the 8 expired pts, 75% had both blast crisis and 2 sxs of leukostasis; 38% had intracranial hemorrhage or CVA; and 88% were hypotensive, receiving mechanical ventilation, and unable to tolerate induction chemotherapy.

Conclusion:
Carefully selected patients with acute leukemia and evidence of impending thrombosis may benefit significantly from leukapheresis therapy. A limited number of treatments (median of 2 treatments) can enable a high percentage of patients to receive induction chemotherapy and may improve short-term clinical outcomes. Leukapheresis treatments are considered emergency procedures as they are often life saving.

Disclosures:
Hofmann: Fresenius Medical Care: Consultancy. Kiprov:Fresenius Medical Care: Employment.