Treatment of pediatric myelodysplastic syndromes and juvenile myelomonocytic leukemia: the Brazilian experience in the past decade

Allogeneic hematopoietic stem cell transplantation in pediatric myelodysplastic syndromes: a multicenter experience from Argentina

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (AHSCT) represents the only curative treatment for the majority of pediatric patients with Myelodysplastic Syndrome (MDS). We aimed to evaluate overall survival (OS), disease-free survival (DFS), non-relapse mortality (NRM) and relapse incidence in children who underwent AHSCT for MDS in six institutions from Argentina.

PROCEDURE

A retrospective analysis of 54 AHSCT was carried out in 52 patients (mean age: 9 years; range: 2-19; 35 males).

RESULTS

MDS subtypes were refractory cytopenia of childhood (RCC) (n: 26, 50%), refractory anemia with excess blasts (RAEB) (n: 9, 18%), RAEB in transformation (RAEB-T) (n: 8, 15%) and juvenile myelomonocytic leukemia (JMML) (n: 9, 17%). At time of transplant, seven (13%) patients transformed to acute myeloid leukemia (AML) and two patients with RCC to RAEB. Donors were related in 32 cases (59%) and the stem cells source was: bone marrow (63%), peripheral blood (26%), and umbilical cord blood (11%). Five-year DFS and OS were 50% and 55% respectively; and for patients with JMML, 57% and 67% respectively. Cumulative incidence of NRM and relapse were 27% and 21% respectively. In the multivariate analysis, umbilical cord blood (HR 4.07; P = 0.025) and age ≥ 9 years at transplantation (HR 3.28; P = 0.017) were associated with lower OS; age and graft-versus-host disease (GVHD) had a higher NRM.

CONCLUSIONS

In our series, more than half of the patients achieved long term OS with AHSCT. Less toxic conditioning regimens or more intensive GVHD prophylaxis could lead to better results in some children.

Array-CGH as an adjuvant tool in cytogenetic diagnosis of pediatric MDS and JMML

Myelodysplastic syndromes (MDS) and juvenile myelomonocytic leukemia (JMML) are rare clonal hematopoietic diseases presented in the childhood. Both diseases exhibit abnormal karyotype and/or monosomy of chromosome 7 in a subgroup of patients. We screened for copy number variations (CNVs) by array-comparative genomic hybridization (aCHG) the DNA from bone marrow of six MDS and four JMML pediatric patients. Array-CGH analysis identified five cases (50%) with monosomy 7, disclosing the chromosome 7 monosomy in two patients whose samples could not be evaluated by other methods. We identified CNVs in six patients, one of which displayed loss of LMO2, an oncogene that plays a central role in hematopoietic development. Our results suggest that array-CGH is a reliable and accurate technique to identify genomic alterations in MDS and JMML.

Aberrant methylation in pediatric myelodysplastic syndrome

BACKGROUND

Aberrant methylation of gene promoter region is responsible for inappropriate gene silencing, and it has been associated to initiation and progression of cancer. Aberrant promoter methylation is frequently observed in adult patients with myelodysplastic syndrome (MDS), but in pediatric patients it has been poorly investigated.

METHODS

We examined the promoter methylation status of 13 genes in bone marrow cells collected at diagnosis of 21 pediatric patients with MDS (subtype RAEB or RAEB-t). For this analysis, we performed sodium bisulfite treatment of genomic DNA, followed by methylation specific PCR (MSP).

RESULTS

In pediatric MDS samples, we observed two genes frequently methylated: CALCA was methylated in 85.7% (18/21) of the analyzed samples and CDKN2B in 50% (6/12).

CONCLUSIONS

Our findings indicate that CALCA and CDKN2B are frequently methylated in pediatric MDS. It suggests that aberrant methylation in pediatric MDS seems to be similar to adult MDS, thus pediatric patients could be also benefited with treatment using demethylating agents.