Nonmyeloablative conditioning regimens and bone marrow transplantation--some contemporary aspects.

The extensive use of bone marrow transplantation (BMT) in the treatment of a number of life threatening hematologic, oncologic and immunodeficiency disorders has come as a result of more than four decades of research and clinical experience. It is estimated that about 50,000 BMT per year are currently performed at more than 500 clinical centers all over the world. Total body irradiation (TBI) in combination with intensive chemotherapy (CT) proves to be a method without alternative in the preparation of patients with hematologic diseases for bone marrow or hematopoietic stem cells transplantation. Fractionated TBI is applied in myeloablative regimens where patients receive between 10 and 15 Gy. In the recent decade establishing the immunoreactivity of the graft lead to the introduction of nonmyeloablative conditioning regimens, including TBI, most often with a single dose of the order of 2 Gy received before transplantation. It is only in the last decade that the Bulgarian onco-radiologic community extended its knowledge and experience in the field of bone marrow transplantology. The first autologous BMT in Bulgaria was carried out in 1997, the first allogeneic BMT with conditioning TBI regimen--in 2002 and the first BMT with nonmyeloablative conditioning regimen including TBI with 2 Gy--in 2005. AIM OF The aim of the present review was to go over some aspects of the clinical experience that has been accumulated for the last ten years in the field of nonmyeloablative conditioning regimens and BMT. We also survey the basis for developing nonmyeloablative conditioning regimens, their aims and purposes, the main indications for their application, observed toxicity and therapeutic efficiency. The clinical experience gained in the last decade shows unambiguously that the BMT with conditioning "mini" TBI regimen, owing to the graft-versus-leukemia or graft-versus-tumor effect, is capable of achieving remission in patients with life threatening, conventional treatment-resistant hematologic, limphoproliferative disorders and some solid tumor.