Improved Outcome After Reduced Intensity Allogeneic Hematopoietic Stem Cell Transplantation (RI-HCT) for Myelodysplastic Syndrome (MDS) Using Tacrolimus/Sirolimus-Based Gvhd Prophylaxis.

Abstract 2771

Poster Board II-747

We previously reported an encouraging result with RI-HCT for MDS (Bone Marrow Transplant 2007; 40:843-50) using flugarabine/melphalan conditioning and cyclosporine (CSA)/mycophenolate (MMF) as GVHD prophylaxis. In order to further improve upon the outcome in the RI-HCT setting, we initiated a series of clinical trials at City of Hope National Medical Center designed to evaluate the impact of tacrolimus (FK)/sirolimus (SIRO)-based GVHD prophylaxis. Here we report the combined, updated results from a consecutive case-series of 89 patients with MDS (including AML progressed from MDS) who underwent RI-HCT from 2000 to 2008 and received either CSA/MMF (n =44) or FK/SIRO (n=45)-based GVHD prophylaxis. All patients received fludarabine 125 mg/m² plus melphalan 140 mg/m² followed by an allogeneic HCT (peripheral blood: n=83, bone marrow: n=6) from an HLA-identical sibling (SIB: n=35) or unrelated donor (MUD: n=54). Additional ATG was given to 12 patients. For MUD transplants a short course of methotrexate was added to CSA/MMF or FK/SIRO. The median age was 59 years (range: 20-71) and 31 (35%) patients were female, 58 (65%) were male. Diagnoses at transplant were RA (n=21), RARS (n=1), RAEB/RAEBT (n=36), and AML from prior MDS (n=31). Cytogenetic risk was low in 15 (17%), intermediate in 37 (41.5%), high in 37 (41.5%) patients. By IPSS criteria (for MDS only), 2 patients had low, 24 had int-1, 20 had int-2, and 12 had high-risk MDS. Twenty-seven patients had therapy-related MDS including 14 with prior autologous HCT. The median follow-up time for surviving patients was 39 months (range: 24-68) for the CSA/MMF group and 17 months (range: 4-39) for the FK/SIRO group. All but two patients (1 in CSA/MMF, 1 in FK/SIRO) engrafted with the median neutrophil recovery at 15 days (range: 11-55). The baseline patient, disease and transplant characteristics were similar between CSA/MMF and FK/SIRO, except for an increased percentage of therap-related MDS in the CSA/MMF group (43% vs. 18%, p<0.01). The median donor chimerism by STR at day 30 post-transplant was 100% in both groups (p=0.6). FK/SIRO was associated with a significantly reduced one-year non-relapse mortality (NRM) (11.4%) compared with CSA/MMF (36.2%, p=0.01). This improvement in NRM translated into a trend for improved overall survival (81.4% vs. 52.3%, p=0.1) and disease-free survival (72.2% vs. 52.3%, p=0.08) at one year. While we observed no significant difference in acute GVHD grade II-IV between CSA/MMF and FK/SIRO, FK/SIRO was associated with a significant reduction in grade IV GVHD (0% versus 26%, p<0.01) and a trend for III-IV GVHD (31% vs. 55%, p=0.1). There was no significant difference in chronic GVHD between FK/SIRO (60%) and CSA/MMF (56%, p=0.8). In multivariate analysis, the use of FK/SIRO was independently associated with improved NRM after adjusted for donor type, therapy-related MDS, %bone marrow blasts, and HLA match status (Table). In conclusion, FK/SIRO-based GVHD prophylaxis was associated with an improved outcome after RI-HCT for MDS attributable to the reduced risk for severe acute GVHD.