Allogeneic Stem Cell Transplantation for Patients with Chronic Myeloid Leukemia After Prior Treatment with Nilotinib or Dasatinib

Abstract 2348

Stem cell transplantation (SCT) will continue to be a treatment option for patients with chronic myeloid leukemia, despite the introduction of tyrosine kinase inhibitors (TKI). However, many patients will have received prior therapy with TKI, including Nilotinib or Dasatinib at the time of allogeneic SCT. While the use of Imatinib prior to SCT seems to have no adverse impact on the outcome of allogeneic SCT little is known on the impact of prior use of second generation TKI. Therefore we conducted a retrospective registry study and identified 56 patients with CML who received an allotransplant after having been treated with Nilotinib and/or Dasatinib. Best responses to second generation TKI were major molecular response in 11%, complete cytogenetic response in 7%, partial cytogenetic response in 18%, complete hematologic remission in 25% and no response in 34%, respectively. At SCT, 37% of the patients were in accelerated or in blast phase, 36% in CP2 or higher and 27% in first chronic phase. Graft failure occurred in two patients. The median follow-up for surviving patients is 19 months. At 24 months the estimated non-relapse mortality was 33% and the relapse incidence 15%. Probability of survival is more than 85% at 2 years in patients transplanted in CP1. In univariate analysis there was a non significant trend in favor for pretreatment with Nilotinib as compared to the other groups. However, in multivariate analysis only stage of the disease was a predictor for survival. With respect to overall survival no significant differences could be identified for the following variables: patient age, donor type, stem cell source, intensity of the conditioning, time diagnosis to transplant, in or ex vivo T-cell depletion, response to treatment with second generation TKI. Patients transplanted in blast crisis had a significant higher risk of non relapse mortality. In summary, despite the shortcomings of a retrospective study, the data reported clearly show the feasibility and efficacy of allo SCT in patients pretreated with second generation TKI and it should be emphasized that the timing of allogeneic stem cell transplantation remains crucial to avoid unacceptable high treatment related mortality.