Patients and Methods: Between 10/04 and 6/06, 24 patients (pts) with high risk/relapsed/refractory hematologic malignancies have undergone NST using a modification of our original Pt-TBI regimen. The median age was 60 years. The median number of prior therapies was 2 (range 0-6). Diseases transplanted included acute lymphoblastic leukemia (nϭ3), myelodysplastic syndrome (nϭ2), acute myelogenous leukemia (nϭ8), chronic lymphocytic leukemia (nϭ3), indolent non-Hodgkin's lymphoma (nϭ2), and mantle

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... cell lymphoma (nϭ6). Conditioning consisted of Pentostatin 4 mg/m2 daily on day -10, -9, and -8, followed by 200 cGy TBI on day -1. Post-grafting immunosuppression consisted of cyclosporine/mycophenolate mofetil. Results: Transplantation was performed using mobilized progenitor cells from matched related (nϭ8) or unrelated (nϭ16) donors. Death prior to 100 days post transplant occurred in 4 unrelated donor transplants. The median nadir values for hemoglobin, neutrophil count and platelet count were 8.9 g/dl (range 7.6-13.7), 300/mm 3 (range 0-1900), and 63/mm 3 (range 9-165) respectively. Primary graft failure/autologous recovery occurred in one patient with mantle cell lymphoma. The median values for CD3ϩ cells and WBC at day 28 were 85% and 90% donor cells respectively. The analogous median values at day 70 were 85% and 100% respectively. One pt with a myelproliferative disorder and thalidomide as his only prior therapy experienced late graft failure despite donor lymphocyte infusions. The cumulative incidence of grade II-IV acute graftversus-host disease was approximately 54% (14% in related versus 68% in unrelated donors, Pϭ0.08). The probability of extensive chronic graft-versus-host disease in patients surviving beyond 100 days is 38%. The cumulative incidence of relapse at one year post transplant is 43%. The one year probabilities of event-free and overall survival are 41% and 61% respectively. Conclusions: This modification of our original Pt-TBI regimen continues to demonstrate fairly minimal regimen related toxicity, although as expected hematologic toxicity appears to be more significant than with our prior day -21 Pentostatin regimen. Graft versus host disease continues to be a major cause of morbidity/mortality, particularly in unrelated donor transplants. Further studies will concentrate on attempting to decrease the incidence of acute and chronic graft versus host disease through the use of T-cell depletion with in vitro alemtuzumab. Timely availability of matched donors limits allo-hematopoietic transplant (HCT) options for many otherwise suitable patients. We have explored sirolimus (rapamycin) based immuno-Poster Session II 84