OBJECTIVETo evaluate the use of a new reduced intensity of BuCy conditioning regimen for the treatment of malignant hematologic diseases in aged or intolerable patients receiving allogeneic hematopoietic stem cell transplantation (allo-HSCT) from the siblings.

METHODSTwelve patients with acute lymphoblastic leukemia (ALL, n = 4), acute myelogenous leukemia (AML-M(2), n = 2), chronic myelogenous leukemia (CML, n = 4), and myelodysplastic syndromes-refractory anemia with excess blasts (MDS-RAEB, n = 2) were intolerant of conventional myeloablative therapy because of age (older than 50 years) or having severe concurrent diseases. The median age was 49 years (range 42-64 years). Seven were males and five females. Two of the 12 patients were HLA one antigen-mismatched and the rest HLA identical with their donors. The low dosage conditioning regimen consisted of busulfan (2 mg.kg(-1).d(-1) for 3 days), Ara-C (2 g.m(-2).d(-1) for 1 or 2 times), cyclophosphamide (1.0 g.m(-2).d(-1) for 2 days) and anti-T-lymphocyte globulin (ATG 2.5 mg.kg(-1).d(-1) for 4 days, -5 - -2 day). Granulocyte colony-stimulating factor mobilized bone marrow and peripheral blood stem cells (PBSC) were harvested (1 patient using PBSC alone). All patients received cyclosporin A, short-term MTX and mycophenolate mofetil (MMF) for prophylaxis of acute graft-versus-host disease (aGVHD). DNA short tandem repeat (STR) sequence analysis, cytogenetics and molecular-biologic technique were used to analyze chimerism.

RESULTSAll the patients were well tolerated the regimen, with no severe regimen related toxicity. In all the 12 patients, absolute neutrophil count > or = 0.5 x10(9)/L was achieved in 11 to 17 (median 15) days and platelet count > 20 x 10(9)/L in 10 to 23 (median 15) days after transplantation. Complete chimerism was achieved in 11 patients and 1 patient was in mixed chimerism at one month after HSCT. With a median follow-up of 14.5 (4.0-24.0) months, 7 of the 12 patients (58.0%) were alive and 5 (42.0%) of the 7 were disease-free. The probabilities of OS and DFS at 12 months were 75.0% and 48.1%. Five patients (41.6%) had aGVHD and four had local chronic GVHD with a cumulative probability of chronic GVHD of 41.5%.

CONCLUSIONThis reduced intensity conditioning regimen is well tolerated and safe for HSCT in the older patients or patients with severe concurrent medical conditions and can achieve full chimerism and long-term disease-free survival.