Table 5. Diagnostic Criteria for Juvenile Myelomonocytic Leukemia (JMML) continued...
Historically, more than 90% of patients with JMML died despite the use of chemotherapy, but with the application of hematopoietic stem cell transplant (HSCT), survival rates of approximately 50% are now reported. Patients appeared to follow three distinct clinical courses: (1) rapidly progressive disease and early demise; (2) transiently stable disease followed by progression and death; and (3) clinical improvement that lasted up to 9 years before progression or, rarely, long-term survival. Favorable prognostic factors for survival after any therapy include being younger than 3 years, having a platelet count of greater than 33 × 109 /L, and low age-adjusted fetal hemoglobin levels.[8,20] In contrast, being older than 3 years and having high blood fetal hemoglobin levels at diagnosis are predictors of poor outcome.[8,20] It remains controversial whether specific mutations are predictive of outcome.
The role of conventional antileukemia therapy in the treatment of JMML is not defined. The absence of consensus response criteria for JMML complicates determination of the role of specific agents in the treatment of JMML. Some of the agents that have shown antileukemia activity against JMML include etoposide, cytarabine, thiopurines (thioguanine and 6-mercaptopurine), and isotretinoin, but none of these have been shown to improve outcome.[21,22,23,24,25]
HSCT offers the best chance of cure for JMML.[19,26,27,28] A report from the European Working Group on Childhood myelodysplastic syndrome notes a 55% and 49% 5-year event-free survival for a large group of children with JMML transplanted with HLA-identical matched family donors or unrelated donors, respectively. The trial included 100 recipients at multiple centers using a common preparative regimen of busulfan, cyclophosphamide, and melphalan, with or without antithymocyte globulin. Recipients had been treated with varying degrees of pretransplant chemotherapy or differentiating agents and some patients had splenectomy performed. Multivariate analysis showed no effect on survival of prior AML-like chemotherapy versus low-dose chemotherapy or none; no effect on survival was observed for the presence or absence of a spleen, difference in spleen size, or related versus unrelated donors. Only gender and age older than 4 years were shown to be poor prognostic factors for outcome (relative risk [RR] 2.24 [1.07–4.69], P = .032, RR 2.22 [1.09–4.50], P = .028 for older age and female gender, respectively). The use of reduced-intensity preparative regimens in order to reduce the adverse side effects of transplantation have also been reported in small numbers of patients, with variable success.[29,30]
Disease recurrence is the primary cause of treatment failure for children with JMML following HSCT and occurs in 30% to 40% of cases.[19,26,27] While the role of donor lymphocyte infusions is uncertain, it has been reported that approximately 50% of patients with relapsed JMML can be successfully treated with a second HSCT.