RESUMEN
Juvenile myelomonocytic leukemia (JMML) is a rare, aggressive clonal myeloproliferative disorder of infancy and early childhood caused by oncogenic mutations in genes involved in the Ras pathway. Long-term survival has only been achieved with hematopoietic stem cell transplantation (HSCT), being able to cure more than 50% patients. To manage the disease before HSCT remains an important issue with constant searching for optimal treatment modalities. According to several retrospective analyses, azacitidine (AZA) induced clinical and molecular responses in patients with relapsed JMML pre-transplant and post-transplant, suggesting its use as a promising "bridging" therapy before HSCT. In this paper we report our first consecutive cohort of patients with JMML treated at our institution as well as our experience with the diagnosis, novel treatment and management of these patients before the HSCT. We present 6 patients with JMML, harboring different somatic mutations (PTPN11 and NRAS), with distinct clinical features; 3 of them had been treated with AZA 75 mg/m2 i.v. on days 1 to 7 of a 28-day cycle before the HSCT. Response to therapy was evaluated after each cycle in accordance with the International response criteria. One patient had a progression of splenomegaly during the treatment and after three cycles he was urgently transplanted. At the present, he is remaining in complete remission 3 years after HSCT. Two patients showed impressive response following the first cycle of the therapy with a regression of splenomegaly and monocyte count, normalized leukocytes, platelets and absent blasts in peripheral blood. The treatment was well tolerated with no adverse effect recorded. The clinical activity and favorable toxicity of AZA in JMML provide a rationale for its use as a "bridging" therapy before HSCT. Prospective trials with accompanying translational studies are required to provide further information regarding individual factors that may direct the most appropriate choice of pretransplantation therapy.