Childhood acute lymphoblastic leukemia with hyperleukocytosis at presentation.

Background: Hyperleukocytosis caused by acute lymphoblastic leukemia (ALL) is associated with early morbidity and mortality due to hyperviscosity arising from the excessive number of leukocytes.This study was designed to assess the incidence of hyperleukocytosis, survival outcomes, and adverse features among pediatric ALL patients with hyperleukocytosis.

Methods: Between January 2001 and December 2010, 104 children with previously untreated ALL were enrolled at the Pusan National University Hospital. All of them were initially stratified based on the National Cancer Institute (NCI) risk; 48 (46.2%) were diagnosed with high-risk ALL. The medical charts of these patients were retrospectively reviewed.

Results: Twenty (19.2%) of the 104 children with ALL had initial leukocyte counts of >100×10(9)/L, and 11 patients had a leukocyte count of >200×10(9)/L. Male gender, T-cell phenotype, and massive splenomegaly were positively associated with hyperleukocytosis. Common early complications during induction therapy included renal dysfunction, and central nervous system hemorrhage. The complete remission (CR) rate for the pediatric ALL patients with hyperleukocytosis (94.1%) was similar to the overall CR rate (95.6%). The estimated 3-year event free survival (EFS) and overall survival of ALL children with hyperleukocytosis were 75.0% and 81.2%, respectively. However, patients with initial leukocyte counts >200×10(9)/L had a lower EFS than those with initial leukocyte counts 100-200×10(9)/L (63.6% vs. 100%; P=0.046).

Conclusion: The outcome of pediatric ALL cases with an initial leukocyte count >200×10(9)/L was very poor, probably due to early toxicity-related death during induction therapy.