Treatment of acute myeloid leukemia (AML) in first remission (CR1) with unrelated donor (UD) allogeneic hematopoietic cell transplantation (HCT).

Abstract

6532 Background: The benefit of allogeneic HCT in patients with AML in CR1 is frequently offset by excessive transplant related mortality (TRM), which can deny the benefit of the graft-versus-leukemia effect. Conversely, decreasing TRM while preserving antileukemic activity can have marked impact on outcomes. Methods: We transplanted 44 patients in CR1 using the conditioning regimen of IV busulfan (Bu)130 mg/m2 (day-6 to -3), fludarabine (Flu) 40 mg/m2 (day-6 to -3) and antithymocyte globulin (4.0 mg/kg). Graft-versus-host-disease (GVHD) prophylaxis consisted of mini-MTX and tacrolimus, with (n=14) or without pentostatin (n=30). High-resolution allele level HLA typing was performed for all donors/recipients (HLA-A, B, C, DRB1, DQB1 and DPB1). Eligibility: age<65, high/intermediate risk AML. Results: Median age was 48 (range: 13-63) years; 7 patients (16%) had secondary AML. Cytogenetic risk class: intermediate, 41% (N=18), good, 1 case (with CNS disease), and poor, 57% (N=25). Stem cell source was bone marrow in 68% (N=30) and peripheral blood in 32% (N=14). Median follow-up is 28 months. All patients engrafted. Grade II-IV acute (a) GVHD rate was 14% (N=2) in patients who received and 27% (N=8) for those who did not receive pentostatin. Chronic (c) GVHD rate was 39% (N=17; extensive in 7). 100-day and 3-year TRM rate was 5% (N=2) and 16% (N=7), respectively. Six patients (14%) have relapsed and 10 patients (23%) have died (3 of relapse and 7 of TRM causes). 3-year event-free and over all survival is 70% and 78%, respectively. For key outcomes see Table. Conclusions: UD HCT after the myeloablative, reduced toxicity IV Bu-Flu regimen for patients with AML in CR1 yields excellent disease control with low risk for TRM. Patient, disease, and donor characteristics (N)—median follow-up is 28 months 3-year actuarial event-free survival (%) (p value) 3-year actuarial overall survival (%) (p value) All patients (n=44) 70 78 Secondary AML Yes (n=7) 57 (0.4) 56 (0.2) No (n=37) 73 84 Cytogenetic risk category Intermediate (n=18) 82 (0.5) 83 (0.9) Poor (n=25) 62 78 HLA 10/10 Yes (n=39) 70 (0.6) 78 (0.9) No (n=)5 80 80 HLA-DPB1 mismatch 0 (n=11) 58 (0.4) 63 (0.5) 1 (n=22) 78 80 2 (n=11) 78 90 No significant financial relationships to disclose.