Graft-versus-host disease is not associated with reduced incidence of relapse following haploidentical stem cell transplantation with post-transplant cyclophosphamide for acute lymphoblastic leukaemia: A study on behalf of the Acute Leukaemia Working Party of European Society for Blood and Marrow Transplantation

The graft-versus-leukaemia effect (GVL) is closely associated with graft-versus-host disease (GVHD) after human leucocyte antigen (HLA)-matched allogeneic stem-cell transplantation (SCT) in acute lymphoblastic leukaemia (ALL). However, there are no data on this association following haploidentical SCT (haploSCT) with post-transplant cyclophosphamide (PTCy). We assessed the impact of acute and chronic GVHD on haploSCT outcomes in 516 adult ALL patients. The cumulative incidence of acute GVHD grade II–IV and III–IV, chronic GVHD and extensive chronic GVHD was 33.3%, 11.7%, 35.3% and 11.8% respectively. The 2-year relapse incidence (RI), non-relapse mortality (NRM) and overall survival (OS) were 27.1%, 17.3% and 64.4% respectively. The time-dependent hazard ratios (HRs) of acute GVHD grade II, grade III–IV, limited and extensive chronic GVHD associated with RI were 0.92 (95% confidence interval [CI] 0.58–1.48, p = 0.74), 0.57 (95% CI, 0.27–1.22, p = 0.15), 1.06 (95% CI, 0.62–1.82, p = 0.83) and 0.95 (95% CI, 0.42–2.17, p = 0.91) respectively. Acute GVHD grade III–IV and extensive chronic GVHD were associated with higher NRM (hazard ratio [HR] 1.95 [95% CI, 1.09–3.48, p = 0.002] and 3.3 [95% CI, 1.41–7.73, p = 0.006]) and reduced OS (HR 1.91 [95% CI, 1.07–3.39, p = 0.03] and 3.27 [95% CI, 1.4–7.66, p = 0.006]) respectively. In conclusion, acute and chronic GVHD are not statistically associated with reduced RI after haploSCT with PTCy in ALL. Higher GVHD grades are associated with higher NRM and lower OS.