Allogeneic or haploidentical HSCT for refractory or relapsed solid tumors in children: toward a neuroblastoma model

New concepts of allogeneic hematopoietic SCT (allo-HSCT) for neuroblastoma and other solid tumors do not rely on escalation of chemotherapy intensity and tumor load reduction but rather on a graft-vs-tumor effect. At this point, this is still an investigational and unusual application of allogeneic transplant, with 78 neuroblastoma patients reported to the European Group for Blood and Marrow Transplantation activity survey from 2002 to 2007 and less than 100 published cases. Two trends can be observed in the reviewed data: some teams have used allo-HSCT in children with refractory or progressive disease and significant tumor burden and other teams in children with CR, PR or minimal residual disease earlier in their disease process. Early studies of allo-HSCT in children with high-risk neuroblastoma suggest that this is a feasible approach that may improve outcome in this deadly disease. However, the proper timing for allo-HSCT during the disease course remains to be determined.