Allogeneic Stem Cell Transplantation for Patients with AML and FLT-3 Mutations.

Abstract 4573

Patients with acute myeloid leukemia (AML) with FLT-3 mutations have an extremely high risk of relapse after conventional chemotherapy. The role of allogeneic stem cell transplantation (SCT) for this patient cohort has been discussed controversially in recent years. This retrospective analysis reports our cumulative experience in a cohort of 42 consecutive patients (age 17–70, median 51 years) allografted for FLT-3 positive AML in a single centre. In more than 80% a FLAMSA-RIC based conditioning regimen was used, in 5% BCNU/Melphalan/Fludarabine, and in 14% conventional radiation- or Busulfan- based regimens. Most patients received mobilized peripheral blood stem cells as graft and 10 patients had a sibling and 32 an unrelated donor (MUD), respectively. Half of the patients were allografted in complete remission and twenty with active, mostly refractory disease. With a median follow-up for surviving patients of nearly 2 years (range 64 – 1746 days) the Kaplan-Meyer procedure estimates a 48% probability of survival at 2 y after transplantation. Interestingly, there is no difference what so ever in survival if patients had an identical sibling donor or a MUD. Similarly, neither patient age below or above the median, nor the applied conditioning regimen did affect the outcome. The only significant variable for improved survival was being in complete remission at transplantation with a 2-year overall survival probability of 60% as compared to 30% for patients with active disease. Thirteen patients (31%) relapsed after allografting, which is substantially lower as to what is reported after conventional chemotherapy. Three of these patients could be salvaged by a second transplant, whereas 10 patients finally died from leukaemia. Non relapse mortality was 24% with 2 patients dying from acute GVHD, 7 from infections and 1 from suicide, despite being well physically. In conclusion, our data support the notion that allogeneic SCT is a highly effective treatment option for patients with AML and FLT-3 mutations and that, if the patient is eligible, it should be undertaken whenever possible in 1. complete remission. However, even patients with primary induction failure have a reasonable chance to be salvaged by allogeneic SCT.