Allogeneic transplantation using non-myeloablative transplant regimens

Reduced intensity (non-myeloablative) stem cell transplant (NST) preparative regimens are being increasingly used to exploit the curative potential of allogeneic stem cell transplantation without the morbidity and mortality associated with conventional transplantation. Growing confidence in the power of the allogeneic graft-versus-malignancy (GVM) effect makes such an approach attractive. Lower intensity transplants increase the degree of mixed chimerism, both in T cell and myeloid cell lineages. Currently a variety of NST treatment approaches are being developed and in this chapter their safety profile and the immunological characteristics of the mixed chimeric state are described. Results of NST in specific disease categories are still limited but the NST approach appears to have promise in the treatment of both haematological and non-haematological malignancies because of the benefit of low toxicity coupled with a strong graft-versus-malignancy effect. NST regimens are also being explored in high-risk patients with non-malignant disorders. However, at present, there is insufficient data to determine whether NST should replace standard myeloablative transplants in specific disease groups. With their low toxicity, NST are well placed as platforms for future developments in transplant immunology to avoid GVHD and enhance the allograft effect against malignant diseases.