OBJECTIVETo observe the influence of decreasing conditioning regimen intensity on the engraftment of HLA haplotype peripheral blood stem cell transplantation.

METHODTwelve patients with leukemia, including 4 in complete remission, whose HLAs were full matched with donors, and 8 with refractory leukemia, whose HLAs were mismatched, were transplanted with G-CSF mobilized allogeneic peripheral blood stem cells after conditioned with a regimen consisting of fludarabine (30 mg/m(2) x 6 days), busulfan (4 mg/kg x 2 days) and cyclophosphamide (30 approximately 60 mg/kg x 2 days) (FBC). Donor lymphocytes were infused at day + 30, + 60 and + 90 after transplantation, respectively. Hematopoietic reconstitution was observed. Engraftment was documented by the analysis of short tandem repeats with polymerase chain reaction (STR-PCR).

RESULTPatients in HLA haplotype group received a mean number of 4.87 x 10(8)/kg donor mononuclear cells (MNC), with CD(34)(+) cells of 4.58 x 10(6)/kg and patients in HLA identical group a mean number of 4.85 x 10(8)/kg MNC with CD(34)(+) cells of 4.47 x 10(6)/kg. The mean time of white blood cell count more than 1.0 x 10(9)/L was 14 (10 approximately 18) days in HLA matched patients and 29 (11 approximately 90) days in HLA haplotype group. One three locus mismatched patient failed to engraft, but auto-hematopoiesis was recovered on day + 50. Full donor chimerism was observed in all patients except one with mixed chimera. The mixed chimera was converted into full donor chimera after three times donor lymphocyte infusion. One each died from severe acute GVHD, severe VOD and severe chronic GVHD in HLA haplotype group, and one from chronic GVHD in HLA identical group.

CONCLUSIONPatients survived engraftment was not influenced by decreasing conditioning intensity as in this regimen. Haplotype stem cells could be engrafted durable in recipients by this regimen combined with donor lymphocyte infusion.