MYELOABLATIVE BUFLU CONDITIONING IS WELL TOLERATED AND CAN ACHIEVE EVEN BETTER OUTCOMES IN HLA-MISMATCHED DONOR TRANSPLANTATION FOR INTERMEDIATE-AND HIGH-RISK AML PATIENTS IN COMPLETE REMISSION

Yubo Pi, Lihong Wang, Yujun Dong, Hanyun Ren^*

Department of Hematology, Peking University First Hospital, Peking University, Beijing, PR China

Hematopoietic stem cell transplantation (HSCT) is a primary treatment in acute myeloid leukaemia (AML). Achieving stable engraftment and minimizing regimen-related toxicity (RRT) significantly affects the transplant outcome. The conventional BuCy2 conditioning regimen is associated with high RRT. Alternative myeloablative regimens, such as BuFlu, are proven to be effective and well-tolerated in HLA-matched sibling transplantation. To evaluate the efficacy and toxicity of a myeloablative BuFlu conditioning regimen in HLA-mismatched donor transplantation, we retrospectively analysed 91 AML patients who underwent HSCT using a myeloablative BuFlu conditioning regimen during the period between March 2007 to June 2018. Of these patients, 56 received HLA-mismatched related donor (MMRD: n=56) transplantation and 35 received HLA-matched sibling (MRD: n=35) transplantation. All 91 patients achieved full engraftment. No patient died of RRT within 100 days after HSCT, and the 3-year incidence of non-relapse mortality was 7.9% and 9.9% for the MMRD and MRD groups, respectively (P=0.672). The cumulative incidence rates of grade II–IV acute and chronic graft versus host disease were 19.6% and 14.3% for the MMRD and MRD groups, respectively (P=0.471). The 3-year post-HSCT relapse rates were 15.3% and 33.9% for the MMRD and MRD groups, respectively (P=0.039). In the median follow-up time of 40 months (8-123 months), the 3-year overall survival (OS) rates were 80.6% (range, 75.0-86.2%) and 60.2% (range, 51.5–68.9%) (P=.030), and the 3-year disease-free survival (DFS) rates were 77.6% (range, 71.9-83.3%) and 58.5% (range, 49.9-67.1%) (P=.039) for the MMRD and MRD groups, respectively. In summary, this myeloablative BuFlu conditioning regimen resulted in high engraftment and limited toxicity in both MMRD and MRD transplantation. Furthermore, MMRD transplantation showed a lower relapse rate, which might be due to a strong graft-versus-leukaemia effect, and eventually produced better OS and DFS.