Influence of the conditioning regimen on erythrocyte chimerism, graft-versus-host disease and relapse after allogeneic transplantation with lymphocyte depleted marrow.

Three different conditioning regimens were applied to 144 patients undergoing allogeneic bone marrow transplantation (BMT) with HLA identical sibling marrow, depleted of lymphocytes by counterflow centrifugation. All regimens consisted of cyclophosphamide and fractionated total body irradiation (TBI). In 49 patients treated with regimen A the total TBI dose was 9 Gy. In regimen B the dose rate of TBI was increased and anthracyclines were added (n = 65). Thirty patients received regimen C with a total TBI dose of 12 Gy but no anthracyclines. The different conditioning regimens did not influence the percentage of patients with detectable recipient CFU-GM prior to infusion of donor marrow. The incidences of mixed erythrocyte chimerism at 6 months after BMT were 73, 33 and 20% for regimens A, B and C respectively. The conditioning regimen influenced significantly mixed erythrocyte chimerism from 6 to 24 months after BMT. Both age and the conditioning regimen influenced significantly the incidence of acute graft-versus-host disease (GVHD) (p = 0.017 and 0.0001 respectively). Acute GVHD greater than or equal to I occurred in 15, 29 and 77% of the patients treated with regimens A, B and C respectively. The incidence of acute and chronic GVHD was significantly higher in complete donor chimeras than in mixed chimeras (p less than 0.001 and p less than 0.01). The probability of relapse was 43% in 32 and 18% in 43 good risk patients treated with regimens A and B respectively (p = 0.07). Longer follow-up is needed to draw conclusions about relapse in regimen C.(ABSTRACT TRUNCATED AT 250 WORDS)