Allogeneic stem cell transplantation for chronic myeloid leukemia in the TKI era: population-based data from the Swedish CML registry

Two decades after the introduction of tyrosine kinase inhibitors (TKI), a sizeable portion of patients with chronic myeloid leukemia (CML) in chronic phase (CP) still undergo allogeneic stem cell transplantation (allo-HSCT). We investigated the indications for allo-HSCT, clinical outcome, management of relapse, and post-transplant TKI treatment in a population-based setting using the Swedish CML registry. Of 118 CML patients transplanted between 2002 and 2017, 56 (47.4%) received allo-HSCT in first CP, among whom TKI resistance was the most common transplant indication (62.5%). For patients diagnosed with CML in CP at <65 years of age, the cumulative probability of undergoing allo-HSCT within 5 years was 9.7%. Overall 5-year survival was 96.2%, 70.1% and 36.9% when transplanted in first CP, second or later CP, and in accelerated phase or blast crisis, respectively. Risk factors for relapse were EBMT score >2 and reduced intensity conditioning, and for death, CP > 2 at time point of allo-HSCT only. Non-relapse mortality for patients transplanted in CP was 11.6%. Our data indicate that allo-HSCT still constitutes a reasonable therapeutic option for patients with CML in first CP, especially those resistant to TKI treatment, providing high long-term survival and low non-relapse mortality.