PURPOSE: The optimal dose intensity for conditioning prior to allogeneic hematopoietic stem cell transplantation (alloHSCT) for chronic lymphocytic leukemia (CLL) is unknown. METHODS: We retrospectively compared outcomes of patients who received a first alloHCST after non-myeloablative (NMA) and reduced intensity conditioning (RIC). Data of 432 patients with a median age of 55 years were included, of which 86 patients underwent NMA and 346 RIC. RESULTS: The median follow-up after alloHSCT was 4.3 years. Compared to the RIC group, more NMA patients had purine-analog-sensitive disease, were in complete remission and received matched related donor transplantation. After RIC, the probabilities for 5-year OS, EFS, CIR, and NRM were 46%, 38%, 28%, and 35% and after NMA the respective probabilities were 52%, 43%, 25%, and 32%. In multivariate analysis, remission status prior to conditioning but not RIC versus NMA conditioning had a significant impact on CIR, EFS, and OS. CONCLUSION: Presumed higher anti-leukemic activity of RIC versus NMA conditioning did not translate into better outcomes after alloHSCT, but better remission status prior to conditioning did. Effective pathway inhibitor-based salvage therapies combined with NMA conditioning might thus represent the most attractive contemporary approach for alloHSCT for patients with CLL.

• Keywords
• Allogeneic hematopoietic stem cell transplantation, Nonmyeloablative/reduced intensity conditioning, Relapsed/refractory chronic lymphocytic leukemia,
• MeSH
• Busulfan administration & dosage   MeSH
• Leukemia, Lymphocytic, Chronic, B-Cell mortality   pathology   therapy   MeSH
• Cyclophosphamide administration & dosage   MeSH
• Adult MeSH
• Transplantation, Homologous MeSH
• Incidence MeSH
• Remission Induction MeSH
• Combined Modality Therapy MeSH
• Middle Aged MeSH
• Humans MeSH
• Melphalan administration & dosage   MeSH
• Survival Rate MeSH
• Young Adult MeSH
• Follow-Up Studies MeSH
• Graft vs Host Disease epidemiology   mortality   MeSH
• Transplantation Conditioning mortality   MeSH
• Prognosis MeSH
• Antineoplastic Combined Chemotherapy Protocols therapeutic use   MeSH
• Retrospective Studies MeSH
• Aged MeSH
• Hematopoietic Stem Cell Transplantation mortality   MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Young Adult MeSH
• Male MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Comparative Study MeSH
• Names of Substances
• Busulfan MeSH
• Cyclophosphamide MeSH
• Melphalan MeSH