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A study on 315 patients undergoing transplantation with CD34+ selected blood cells from HLA-identical siblings was performed to determine risk factors for acute GVHD (aGVHD). Recipients of a dose of CD34+ cells (x 10(6)/kg) of 2 or less, more than 2 to 4, and more than 4 had a cumulative incidence of aGVHD grades I-IV of 21%, 35%, and 43%, respectively (log-rank P =.01); similarly, recipients of a dose of CD3+ cells (x 10(6)/kg) of 0.05 or less, more than 0.05 to 0.1, and more than 0.1 had a cumulative incidence of aGVHD grades I-IV of 18%, 35%, and 44%, respectively (log-rank P =.007). Using a Cox regression model, 4 independent factors for aGVHD I-IV were identified: increased CD34+ cell dose (P =.02), increased CD3+ cell dose (P =.02), female patients (P =.01), and higher patient age (> 42 years) (P =.007). This study shows, for the first time in T-cell-depleted transplantations, a positive correlation between the number of CD34+ cells and aGVHD and, also, that the number of CD3+ cells necessary to initiate aGVHD is lower than previously reported.

Stem cell factor (SCF) has been shown to synergize with filgrastim to mobilize CD34(+) cells into the peripheral blood. To determine if addition of SCF to chemotherapy and filgrastim reduces the number of leukaphereses required to achieve a target yield of 5 x 10(6) CD34(+) cells/kg, 102 patients with multiple myeloma were randomized to receive mobilization chemotherapy with cyclophosphamide (4 g/m(2)) and either SCF (20 micrograms/kg/d) combined with filgrastim (5 micrograms/kg/d) or filgrastim alone (5 micrograms/kg/d), administered daily until leukaphereses were completed. After collection, patients were treated with myeloablative therapy supported by autologous peripheral blood progenitor cell (PBPC) infusion and filgrastim (5 micrograms/kg/d). There was a significant difference between the treatment groups in the number of leukaphereses required to collect 5 x 10(6) CD34(+) cells/kg (median of 1 v 2 for SCF + filgrastim and filgrastim alone, respectively, P =.008). Patients receiving the combination of SCF plus filgrastim had a 3-fold greater chance of reaching 5 x 10(6) CD34(+) cells/kg in a single leukapheresis compared with patients mobilized with filgrastim alone. The median CD34(+) cell yield was significantly increased for the SCF group in the first leukapheresis (11.3 v 4.0 x 10(6)/kg, P =.003) and all leukaphereses (12.4 v 8.2 x 10(6)/kg, P =.007). Total colony-forming unit-granulocyte-macrophage (CFU-GM) and mononuclear cell counts were also significantly higher in the SCF group in the first leukapheresis and in all leukaphereses. As expected for patients mobilized to an optimal CD34(+) cell yield, the time to engraftment was similar between the 2 treatment groups. Cells mobilized with the combination of SCF plus filgrastim were thus considered effective and safe for achieving rapid engraftment. Treatment with SCF plus filgrastim was well tolerated, with mild to moderate injection site reactions being the most frequently reported adverse events. There were no serious allergic-like reactions to SCF. The addition of SCF to filgrastim after cyclophosphamide for PBPC mobilization resulted in a significant increase in CD34(+) cell yield and a concomitant reduction in the number of leukaphereses required to collect an optimal harvest of 5 x 10(6) CD34(+) cells/kg.