Prognostic Impact of Extramedullary Infiltration in Pediatric Low-risk Acute Myeloid Leukemia: A Retrospective Single-center Study Over 10 Years

We retrospectively analyzed characteristics and outcomes of low-risk acute myeloid leukemia. The incidence rates of extramedullary infiltration, myeloid sarcoma, and central nervous system leukemia in this study were 24.76%, 20.56%, and 5.61%, respectively. Patients with extramedullary infiltration had worse 3-year relapse-free survival (67.0% +/- 6.6% vs. 86.9% +/- 2.9%; P = .000) and worse 3-year overall survival (76.1% +/- 6.2% vs. 87.8% +/- 2.8%; P=.026). Myeloid sarcoma was an independent risk factor for poor relapse-free survival (hazard ratio, 2.640; 95% confidence interval, 1.281-5.440; P = .008) and overall survival (hazard ratio, 2.079; 95% confidence interfal, 0.969-4.460; P = .049). Background: The impact of extramedullary infiltration (EMI) on the clinical outcomes of pediatric patients with acute myeloid leukemia (AML) are controversial. Patients and Methods: A total of 214 pediatric patients with low-risk AML were classified as having EMI (central nervous leukemia [CNSL] and/or myeloid sarcoma [MS]) and not having EMI. Patients with isolated MS before AML diagnosis by bone marrow examination were confirmed with histopathologic examination. For patients diagnosed with AML by bone marrow examination, a thorough physical examination and radiologic imaging were used to confirm MS. Results: Male gender, a high white blood cell count, the FAB-M5 subtype, t(8;21) and t(1;11) abnormalities, and c-KIT mutations were associated with EMI. The presence of MS was associated with a low complete remission rate (63.6% vs. 79.4%; P = .000) and poor 3-year relapse-free survival (RFS) (62.6% +/- 7.5% vs. 87.0% +/- 2.8%; P = .000) and 3-year overall survival (73.5% +/- 7% vs. 88.8% +/- 2.6%; P = .011). Multivariate analysis revealed that MS was a poor prognostic factor for RFS and overall survival. Bone infiltration was an independent risk factor for inferior RFS with MS. Patients with CNSL had a low complete remission rate (58.3% vs. 77.2%; P = .045); however, CNSL did not significantly affect the survival of low-risk patients with AML. Conclusion: MS should be considered an independent risk factor to guide stratified treatment. (C) 2020 Elsevier Inc. All rights reserved.