Clinical Characteristics and Treatment Outcomes of Childhood Acute Promyelocytic Leukemia in Korea: a Nationwide Multicenter Retrospective Study by Korean Pediatric Oncology Study Group.

Purpose Acute promyelocytic leukemia (APL) is a rare disease in children and there are some different characteristics between children and adult. We aimed to evaluate incidence, clinical characteristics and treatment outcomes of pediatric APL in Korea. Materials and Methods Seventy-nine pediatric APL patients diagnosed from January 2009 to December 2016 in 16 tertiary medical centers in Korea were reviewed retrospectively. Results Of 801 acute myeloid leukemia(AML) children, 79 (9.9%) were diagnosed with APL. The median age at diagnosis was 10.6 years (range, 1.3-18.0). Male and female ratio was 1:0.93. Thirty patients (38.0%) had WBC count greater than 10x109/L at diagnosis. All patients received induction therapy consisting of all-trans retinoic acid (ATRA) and chemotherapy. Five patients (6.6%) died during induction chemotherapy and 66 (86.8%) patients achieved complete remission (CR) after induction chemotherapy. The causes of death were 3 intracranial hemorrhage (ICH), 1 cerebral infarction, and 1 sepsis. Five patients (7.1%) suffered a relapse during or after maintenance chemotherapy. The estimated 4-year event-free survival rate (EFS) and overall survival rates (OS) were 82.1 ± 4.4%, 89.7 ± 5.1% respectively. The 4-yr OS was significantly higher in patients with initial WBC <10x109/L than in those with initial WBC ≥10x109/L (p=0.02). Conclusion This study showed that the CR rates and survival outcomes in Korean pediatric APL patients were relatively good. The initial WBC count was the most important prognostic factor and most causes of death were related to serious bleeding in the early stage of treatment.