Graft-versus-host disease prophylaxis with post-transplant cyclophosphamide in chronic myeloid leukemia patients undergoing allogeneic hematopoietic cell transplant from either an unrelated or mismatched related donor: a comparative study from the Chr..

Abstract

Outcomes following allogeneic hematopoietic cell transplant (allo-HCT) for Chronic Myeloid Leukemia (CML) with post-transplant cyclophosphamide (PTCy) utilising an unrelated donor (UD) or mismatched related donor (MMRD) remain unknown. We report on a retrospective comparison of PTCy based allo-HCT from an UD, non-PTCy allo-HCT from an UD and PTCy allo-HCT from a MMRD. Inclusion criteria were adult patients with CML undergoing first allo-HCT between 2012 to 2019 from an UD with either PTCy or non-PTCy GvHD prophylaxis and MMRD using PTCy. Primary endpoint was GvHD relapse-free survival (GRFS). A total of 1341 patients were included (82% in the non-PTCy UD cohort). With a median follow-up of 34.9 months, the 3-year GRFS was 43%, 37% and 39% in the non-PTCy UD, PTCy-UD and PTCy MMRD cohorts, respectively (p=0.15). In multivariable analyses, there were no significant differences between the three cohorts regarding OS, PFS, RI and NRM. Factors independently associated with worse OS in the overall cohort were KPS<90 (HR 1.86, 95%CI, 1.41-2.45; p<0.001), older age (HR 1.24, 95%CI, 1.11-1.38; p<0.001) and disease stage (compared to CP1) blast phase HR 2.25, 95% CI, 1.60-3.16; p<0.001, accelerated phase HR 1.63, 95% CI, 1.05-2.54; p=0.03 and CP>2 HR 1.58, 95% CI, 1.15-2.17; p=0.005. These results suggest that allo-HCT in CML utilizing either an UD or MMRD with a PTCy GvHD-based prophylaxis are feasible transplant platforms and that the disease stage at allo-HCT remains a major prognostic factor, highlighting the importance to closely monitor CML patients and propose transplantation when indicated, when still in CP1.