Cytarabine Monotherapy as Bridging Treatment for Hematopoietic Stem Cell Transplantation in Children with Juvenile Myelomonocytic Leukemia / 임상소아혈액종양

ABSTRACT

BACKGROUND: Mutations leading to hyperactivation of the RAS pathway play a critical role in the pathogenesis of juvenile myelomonocytic leukemia (JMML). Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative therapy, and the role of anti-leukemic treatment prior to HSCT is still controversial. In this study, we analyzed the response of cytarabine monotherapy as a bridging therapy for HSCT in children recently diagnosed with JMML.METHODS: We retrospectively reviewed the medical records of patients with JMML at Seoul St. Mary's Hospital from December 2009 to April 2012.RESULTS: A total 7 patients with JMML were diagnosed and treated with chemotherapy and HSCT. At presentation, all patients showed hepatosplenomegaly and the median leukocyte count was 41.9x109/L (range, 34.3-85.0), median monocyte count was 5.6x109/L (range, 2.7-26.3) and median fetal hemoglobin (HbF) was 13.5% (range, 2.8-42.7). Karyotypic abnormalities in bone marrow cells were noted in 2 cases. Three patients had mutation of NRAS and 2 patients had mutation of NF1. One of the patients with NF1 mutations had characteristic clinical features and familial history of neurofibromatosis. All patients were treated with non-intensive sequential cytarabine chemotherapy (70 mg/m2/day, I.V., 4-12 days) before HSCT and achieved complete hematologic response. All patients underwent unrelated (N=2) or familial mismatched (N=5) HSCT, and all patients successfully engrafted. All patients, except one who relapsed, are alive with leukemia free, although the duration of follow-up is short.CONCLUSION: In our cohort of NRAS prevalent patients, non-intensive cytarabine monotherapy was effective as pre-transplant bridging treatment for JMML.