Differing Outcomes of Patients with High Hyperdiploidy and ETV6-RUNX1 Rearrangement in Korean Pediatric Precursor B Cell Acute Lymphoblastic Leukemia

Purpose Recent cooperative trials in pediatric acute lymphoblastic leukemia (ALL) report long-term event-free survival (EFS) of greater than 80%. In this study, we analyzed the outcome and prognostic factors for patients with precursor B cell ALL (n=405) diagnosed during a 10-year period (2005-2015) at our institution. Materials and Methods All patients were treated with a uniform institutional regimen based on four risk groups, except for steroid type; patients diagnosed up till 2008 receiving dexamethasone, while subsequent patients received prednisolone. None of the patients received cranial irradiation in first complete remission. Results The 10-year EFS and overall survival was 76.3%+/- 2.3% and 85.1%+/- 1.9%. Ten-year cumulative incidence of relapse, any central nervous system (CNS) relapse and isolated CNS relapse was 20.8%+/- 2.2%, 3.7%+/- 1.1%, and 2.5%+/- 0.9%, respectively. A comparison of established, good prognosis genetic abnormalities showed that patients with high hyperdiploidy had significantly better EFS than those with ETV6-RUNX1 rearrangement (10-year EFS of 91.2%+/- 3.0% vs. 79.5%+/- 4.4%, p=0.033). For the overall cohort, male sex, infant ALL, initial CNS involvement, and Philadelphia chromosome (+) ALL were significant factors for lower EFS in multivariate study, while high hyperdiploidy conferred favorable outcome. For high and very high risk patients (n=231), high hyperdiploidy was the only significant factor for EFS in multivariate study. Conclusion Regarding good prognosis genetic abnormalities, patients with high hyperdiploidy had significantly better outcome than ETV6-RUNX1(+) patients. High hyperdiploidy was a major, favorable prognostic factor in the overall patient group, as well as the subgroup of patients with higher risk.