Evidence for a GVL effect following reduced-intensity allo-SCT in ALL: a British Society of Blood and Marrow Transplantation study.

Myeloablative allo-SCT decreases relapse incidence (RI) in ALL. Reduced intensity conditioning (RIC) may extend allo-SCT to older and less fit patients. Sixty-nine ALL patients reported to the BSBMT underwent fludarabine-based RIC allo-SCT, 38 from unrelated donors (UD). Forty-four patients received alemtuzumab. ALL was in CR in 64 patients (93%). This was a second or third SCT in 23 patients. Two-year OS and PFS were 36% and 32%, respectively. In multivariate analysis male recipients demonstrated better OS and PFS (hazard ratio (HR) = 0.42, P = 0.008 and HR = 0.45, P = 0.012, respectively). Two-year TRM was 29%: higher with younger age (HR = 0.97/year, P = 0.041), female recipient (HR = 2.55, P = 0.049) and increasing grade of acute GVHD (HR = 1.87, P = 0.001). Two-year RI was 38% and was lower in patients with acute and chronic GVHD (HR = 0.62 per increasing grade, P = 0.035 and HR = 0.52, P = 0.025, respectively). Long-term ALL-free survival is achievable following fludarabine-based RIC allo-SCT. The association between GVHD and decreased RI suggests the presence of a GVL effect.