In the present single institution study of 66 leukaemia patients (28 AML, 23 ALL, 15 CML), the factors influencing haematological recovery after allogeneic bone marrow transplantation (alloBMT) were analysed retrospectively in order to identify the optimal conditions required for a rapid haematological recovery after alloBMT. All patients received GVHD prophylaxis with cyclosporine A plus methotrexate. The mean number of days required to achieve > or = 0.5 x 109/l neutrophil count after alloBMT was 17 (median 17, range 9 to 27 days) and 19 patients (28.8%) had rapid neutrophil recovery within 15 days after alloBMT. The haematological recovery was more rapid in the 38 patients without GVHD or with only grade I GVHD. Furthermore, 50% and 40% of patients receiving 10 (n = 18) or 5 (n = 20) micrograms/kg/day G-CSF had rapid neutrophil recovery within 15 days after alloBMT, versus only 7.1% of patients not receiving G-CSF post-transplant (n = 28), p <0.001. The neutrophil recovery was similar in patients receiving either fresh or cryopreserved allografts and either TBI-containing or busulfan-containing conditioning regimen. A significant correlation was found between neutrophil recovery and either the MNC or CFU-GM content of the allografts, r = 0.33, p <0.01. The mean number of days required for neutrophil recovery was only 16 days (median 16, range 9 to 24 days) in patients receiving allografts containing > 1 x 10(5) CFU-GM/kg (n = 28) versus 19 days (median 19, range 13 to 27 days) in patients receiving allografts containing <1 x 10(5) CFU-GM/kg (n = 35). Three patients receiving allografts containing less than 0.5 x 10(5) CFU-GM/kg had primary neutrophil engraftment failure. The mean number of days required to achieve 20 x 109/l platelet count was 21 (median 20, range 11 to 50 days) and 30 patients (46.9%) had platelet recovery within 20 days after alloBMT. The platelet recovery after alloBMT was not significantly affected by the type of leukaemia, conditioning regimen, or G-CSF administration. The mean number of days required for platelet recovery after alloBMT was only 20 days (median 18 days) in patients receiving allografts containing > 1.0 x 10(5) BFU-E/kg (n = 35) versus 23 days (median 20 days) in patients receiving allografts containing <1.0 x 10(5) BFU-E/kg (n = 24). Seven patients receiving allografts containing less than 0.5 x 10(5) BFU-E/kg had primary platelet engraftment failure. The present study has identified the high number of progenitor cells in the allografts infused and the daily administration of G-CSF post-transplant as the optimal combination for a rapid neutrophil recovery after alloBMT. More significantly, the number of BFU-E in allografts was the most significant factor to determine platelet recovery after alloBMT. The development of GVHD of grade II or more during the first weeks after alloBMT was associated with slower haematological recovery and longer period of fever during neutropenia and hospitalisation.
