Myeloablative intravenous busulfan-containing regimens for allo-HSCT in AML or MDS patients over 54 years old: combined results of three phase II studies

Comparison of fludarabine-based conditioning regimens in adult cord blood transplantation for myeloid malignancy: A retrospective, registry-based study

Fludarabine/busulfan and fludarabine/melphalan are viable options as conditioning regimens. However, the optimal fludarabine-based conditioning in cord blood transplantation (CBT) remains unclear. Therefore, this retrospective, registry-based study aimed to analyze the impact of five fludarabine-containing conditioning regimens on 1395 adult patients (median age, 61 years) with acute myeloid leukemia, myelodysplastic syndrome, and chronic myeloid leukemia who underwent their first CBT. Treatment outcomes of fludarabine combined with melphalan (100-140 mg/m2 ) and low-dose total body irradiation (TBI; FM140T); melphalan (80-99 mg/m2 ) and TBI (FM80T); busulfan (12.8 mg/kg) and melphalan (FB4M); busulfan (12.8 mg/kg) and TBI (FB4T); and busulfan (6.4 mg/kg) and TBI (FB2T) were compared. The 3-year survival rate was 67%, 53%, 44%, 36%, and 39%, respectively (p < .0001). The FM140T survival rate was the most favorable after adjusting for confounders, and the hazard ratios (vs. FM140T) for overall mortality were as follows: FM80T, 1.6 (95% confidence interval [CI], 1.2-2.2); FB4M, 2.1 (95% CI, 1.6-2.8); FB4T, 2.7 (95% CI, 2.0-3.7); and FB2T, 2.2 (95% CI, 1.6-3.1). The better survival observed with FM140T, regardless of the disease, disease risk, age, or transplant year, was attributed to the lower relapse rate and lower non-relapse mortality (NRM) associated with fewer infectious deaths. Conversely, FB4T was associated with a higher relapse rate and higher NRM. The findings indicate that the outcomes of CBT in myeloid malignancies were highly dependent on both the alkylating agent and its dose in combination with fludarabine. Therefore, compared with fludarabine/busulfan-based conditioning, FM140T may be the preferred regimen.

Advantages of Higher Busulfan Dose Intensity in Fludarabine-Combined Conditioning for Patients with Acute Myeloid Leukemia Undergoing Cord Blood Transplantation

The alkylating agent busulfan is commonly used as conditioning in allogeneic hematopoietic stem cell transplantation for acute myeloid leukemia (AML). However, a consensus has not yet been reached regarding the optimal busulfan dose in cord blood transplantation (CBT). Therefore, we conducted this large nationwide cohort study to retrospectively analyze the outcomes of CBT in patients with AML receiving busulfan at intermediate (6.4 mg/kg i.v.; BU2) or higher (12.8 mg/kg i.v.; BU4) doses within a fludarabine/i.v. busulfan (FLU/BU) regimen. Among 475 patients who underwent their first CBT following FLU/BU conditioning between 2007 and 2018, 162 received BU2 and 313 received BU4. Multivariate analysis identified BU4 as a significant factor for longer disease-free survival (hazard ratio [HR], .85; 95% confidence interval [CI], .75 to .97; P = .014) and a lower relapse rate (HR, .84; 95% CI, .72 to .98; P = .030). No significant differences were observed in non-relapse mortality between BU4 and BU2 (HR, 1.05; 95% CI, .88-1.26; P = .57). Subgroup analyses showed that BU4 provided significant benefits for patients who underwent transplantation while not in complete remission (CR) and those age <60 years. Our present results suggest that higher busulfan doses are preferable in patients undergoing CBT, particularly those not in CR and younger patients.

Total body irradiation-based versus busulfan-based myeloablative conditioning for single-unit cord blood transplantation in adults

Comparative studies between total body irradiation (TBI)-based and busulfan-based myeloablative conditioning (MAC) regimens for cord blood transplantation (CBT) have been limited. We retrospectively analyzed the results of single-unit CBT in 333 adult patients who received either TBI-based (n = 258) or busulfan-based (n = 75) MAC regimens at our institute. After adjusting for significant variables in the univariate analysis, there were no significant differences in neutrophil recovery (hazard ratio (HR), 0.88; p = .460), grade III-IV acute graft-versus-host disease (GVHD) (HR: 1.40, p = .410), extensive chronic GVHD (HR: 0.73, p = .380), relapse (HR: 0.61, p = .270), non-relapse mortality (HR: 1.38, p = .420), overall survival (HR: 1.18, p = .637), or event-free survival (HR: 1.08, p = .773), although platelet recovery was lower with marginal significance for the busulfan-based regimen (HR: 0.67, p = .068). In subgroup analysis, TBI-based regimens were superior to busulfan-based regimens in terms of survival for acute lymphoblastic leukemia, but not for myeloid malignancies. Further investigation is warranted even for CBT.