Reduced-intensity conditioning for allogeneic stem cell transplantation in patients with chronic myeloid leukemia is associated with better overall survival but inferior disease-free survival when compared with myeloablative conditioning - a retrospective study of the Czech National Hematopoietic Stem Cell Transplantation Registry.

Allogeneic stem cell transplantation (AlloSCT) has been currently recommended in the treatment of patients with chronic myeloid leukemia (CML) as a second option after imatinib failure or in selected group of patients with high-risk CML and low risk for transplant-related mortality. The actual role of reduced-intensity conditioning (RIC) before AlloSCT in CML patients has not been yet conclusively established. The Czech National Hematopoietic Stem Cell Transplantation Registry has conducted a retrospective analysis of all patients (n=29) transplanted after RIC from the Registry database containing 295 patients with CML transplanted in the Czech Republic in years 1988-2005 and compared them with patients at comparable age (median age 48.3 and 50.6 years, respectively; p=0.587) transplanted during the same period of time using conventional myeloablative conditioning (n=26). Survival advantage of patients transplanted after RIC has been confirmed by log rank test (p=0.036) despite the fact that the relapse rate was significantly higher in RIC group (44.8% versus 0%). Both groups did not differ significantly in the use of voluntary unrelated donors, type of the grafts and in incidence of acute graft versus host disease (GVHD). However, there were trends for higher risk of CML and higher use of unrelated donors in the myeloablative group while peripheral stem cell grafts and chronic GVHD were observed more frequently in the RIC group. Transplant-related mortality was the leading cause of death in both groups of patients. Our results should be interpreted with caution because they may be influenced by small groups of subjects and also the impact of patients with high EBMT risk score on inferior survival in the myeloablative group cannot be fully eliminated. More retrospective and prospective studies are needed to elucidate the actual role of RIC before AlloSCT for CML.