Allogeneic hematopoietic stem cell transplant with reduced-intensity conditioning for chronic lymphocytic leukemia in Sweden: does donor T-cell engraftment 3 months after transplant predict survival?

Thirty-eight adult patients with chronic lymphocytic leukemia (CLL) underwent reduced-intensity conditioning (RIC) allogeneic stem cell transplant (allo-SCT) in Sweden between 1999 and 2007. The cumulative incidences of acute graft-versus-host disease (GVHD) grades II-IV and chronic GVHD were 29% and 47%, respectively. Rates of non-relapse mortality, progression-free survival (PFS) and overall survival (OS) were 18%, 47% and 74% at 1 year, and 21%, 25% and 45% at 5 years, respectively. T-cell chimerism after transplant was measured in 31 out of 34 patients (91%) surviving beyond day +100. Seventeen patients achieved >90% donor T-cell engraftment at 3 months after allo-SCT and, compared with the 12 patients with ≤90% donor T-cell engraftment, they showed favorable PFS at 1 year (82% vs. 33%, p =0.002) and better long-term PFS and OS (p =0.002 and 0.046, respectively). Donor T-cell engraftment of >90% at 3 months after RIC allo-SCT for CLL seems to predict favorable short-term and long-term outcome.