HLA-Identical Umbilical Cord Blood Transplantation from a Sibling Donor in Juvenile myelomonocytic Leukemia

Background: Juvenile myelomonocytic leukemia (JMML) is a rare malignant myeloid disorder in childhood, for which stem cell transplantation is currently the only curative treatment option. Although unrelated donor umbilical cord blood transplantations (UCBTs) have been described, series of HLA-identical sibling donor UCBTs in JMML are not available.

Methods: From the European Working Group on Childhood MDS (EWOG MDS) registry the 5 JMML patients who underwent a fully HLA matched sibling UCBT are described.

Results: The median age at diagnosis was 18 months (range 15–30 months). In one case no mutation analysis was performed, in one case a PTPN11 mutation was found. In the other cases no mutation in RAS or PTPN11 was found. None of the patients had clinical signs of NF1. The conditioning consisted of busulfan, cyclophosphamide and melphalan in four cases and of cyclophosphamide, etoposide and total body irradiation in one case. All patients engrafted slowly. In 3 patients mild acute graft versus host was noticed (grade 1 and 2), no chronic graft versus host was reported. Two patients relapsed after the initianal transplantation and underwent a second transplant with marrow of the initianal donor. One of them is in second complete remission and the other died after a second relapse. One patient developed increased donor chimerism from day 42 without any clinical sign of relapse. She was treated with DLI, 6 mercaptopurine and 13-cis retinoic acid respectively. She is still in complete remission 5 years after transplantation.

Conclusion: This EWOG serie illustrates that, although this needs to be confirmed in larger series, relatively immunologically naive HLA-matched sibling UCBT is feasible in selected cases of JMML.