Allogeneic Transplantation in Elderly Patients with AML and MDS Comparing Reduced-Intensity Conditioning with Flamsa-Busulfan Versus Fludarabine/BCNU/Melphalan

By reducing treatment intensity allogeneic hematopoietic stem cell transplantation (allo-HSCT) has become feasible for elderly patients. Different reduced-intensity conditioning (RIC) regimens are available, but there is little consensus about the optimal preparative regimen to use, in particular with regard to the outcomes counterbalancing the aim of feasibility and tolerability with higher rates of relapse. Here, we retrospectively evaluate the outcome of sequential therapy employing RIC with fludarabine 30 mg/m², cytarabine 2g/m² and amsacrine 100 mg/m² for 4 days (FLAMSA; Schmid C et al. JCO 2005) followed by busulfan 10 x 0.8 mg/kg (FLAMSA-Bu) compared to RIC utilizing fludarabine 5 x 30 mg/m², carmustine (BCNU) 2 x 150 mg/m² and melphalan 110 mg/m² (FBM; Marks R et al. Blood 2008) in elderly patients treated consecutively at our institution between July 2005 and October 2012.

We analyzed the course of 114 patients (pts) with acute myeloid leukemia (AML; n=99) or myelodysplasia (MDS; n=15) aged ≥ 59 years with 59 pts aged ≥ 66 years who were treated with either FLAMSA-Bu (n=66; n=24 ≥ 66 years) or FBM (n=48; n=35 ≥ 66 years). All patients received sero-therapy with anti-thymocyteglobuline (ATG). Median patient age was 66 years for the entire cohort (68 years FBM; 64 years FLAMSA-Bu). 36 patients (75%) of the FBM and 42 patients (63 %) of the FLAMSA-Bu group suffered from high risk disease defined as relapsed or refractory AML or refractory anemia with excess of blasts in transformation (RAEB-T). The hematopoietic cell transplantation comorbidity index (HCT-CI) was higher for the patients of the FBM group than for the FLAMSA-Bu group with 26 (54 %) versus (vs) 24 patients (36 %) scoring ≥ 2 (p 0.085). Graft source after conditioning with FBM/FLAMSA-Bu was bone marrow (1/2), G-CSF mobilized peripheral blood stem cells (40/62) and double-umbilical cord-blood (7/1). In 23 pts (20 %) HLA-matched related and in 91 pts (80 %) HLA-matched unrelated donor transplantation was performed. Engraftment failure was observed in 1 patient after FLAMSA-Bu, while engraftment was achieved in all evaluable patients of the FBM group in a median of 23 days vs 18 days after FLAMSA-Bu (p 0.003), while 7 pts with double-umbilical cord-blood transplantation where included in the FBM group vs 1 pt in the FLAMSA-Bu group. Non-hematological treatment-related acute toxicity ≥ CTC III (gastrointestinal, hepatic, cardiovascular, renal, centralnervous system) occurred in 12/48 pts (25 %) after FBM and in 18/66 pts (27 %) after FLAMSA-Bu. Incidence of severe acute (III-IV) and chronic GvHD was 22.9 %/16.6 % for FBM vs 18.2 %/19.7 % for FLAMSA-Bu, respectively. After conditioning with FBM 2/48 pts vs 9/66 pts after FLAMSA-Bu were diagnosed with a secondary malignancy (p 0.08). Non-relapse mortality (NRM) after 12 months was 26.8 % for FBM versus 25.2 % for the FLAMSA-Bu group. Incidence of relapse after FBM vs FLAMSA-Bu conditioning was 22.9 % vs 15.2 % after 1 year and 31.3 % vs 16.7 % after 2 years. Occurrence of relapse was significantly related to an incomplete or mixed chimerism (donor cells ≤ 95 % in peripheral blood and/or bone marrow) at day +30 (p 0.001).

After a median follow up of 31.4 months (range 4.4-97.5) estimated overall survival (OS) and relapse-free survival (RFS) after 2 years was 55.4 % and 51.4 % for the FBM vs 58 % and 56.7 % for the FLAMSA-Bu group, respectively. Analyzing different subgroups, FBM conditioning might be favorable for pts aged ≥ 66 years when suffering from high risk AML (n=26): Within this group 1-year OS after FBM vs FLAMSA-Bu was 71.4 % vs 66.7 % (p 0.58) and 1-year RFS was 71.4 % vs 58.3 % (p 0.59), respectively. Notably, for pts at highest risk (aged ≥ 66 years and suffering from secondary or therapy-related AML; n=24) the benefit of FBM conditioning becomes more pronounced: 1-year OS after FBM vs FLAMSA-Bu was 62.5 % vs 37.5 % (p 0.26) and 1-year RFS 54.2 % vs 37.5 % (p 0.17).

Both conditioning regimens are feasible, and provide similar rates of acute toxicity, NRM and GvHD. There might be evidence for a benefit of conditioning with FBM for the subgroup of “the oldest patients at highest risk”. Taking into account that there is an increasing group of ‘medically fit’ elderly patients in the field of allogeneic transplantation, prospective clinical trials are needed to investigate different conditioning regimens considering their special requirements.