UNRELATED DONOR BONE-MARROW TRANSPLANTATION WITHOUT T-CELL DEPLETION USING A CHEMOTHERAPY ONLY CONDITIONING REGIMEN - LOW INCIDENCE OF FAILED ENGRAFTMENT AND SEVERE ACUTE GVHD

Twenty-five patients with hematologic malignancies were treated with b usulfan (16 mg/kg) and cyclophosphamide (50 mg/kg x 3 days) as conditi oning for bone marrow transplantation using marrow from serologically matched, DR locus genotypically identical unrelated donors, Previous s tudies of BuCy2 as conditioning for UD-BMT have reported a graft failu re rate of up to 21% suggesting it may be insufficiently immunosuppres sive in this setting, We elected not to use BuCy4 as it may have a hig her incidence of extramedullary toxicity, In addition the patients rec eived GM-CSF (500 mg/m(2)) from day 0, cyclosporine and short-course m ethotrexate (15 mg/m(2) x 1, then 10 mg/m(2) x 3) as GVHD prophylaxis and prophylactic ganciclovir at engraftment if either they or their do nor were CMV antibody positive, The median age of the 25 patients was 41 years and the most common diagnosis was CML (76%), Seven patients w ere considered poor risk and eight males were recipients of marrow fro m female donors, Sixteen patients survive at a median of 435 days from transplant, The actuarial overall and disease-free survivals at 1 yea r in this group of older patients were 62 +/- 20% and 57 +/- 20% and 1 00-day survival was 70%, The engraftment rate was 100%; there have bee n no instances of secondary graft failure, Fifteen patients (60%) deve loped grade II-IV GVHD and 12 of 16 (75%) developed some chronic GVHD but only half of these were extensive, The performance status of survi vors is good (median of 90); seven of 12 eligible patients are back at work, This study demonstrates that UD-BMT can be successfully perform ed in very closely HLA-matched older patients using a chemotherapy-onl y protocol and that low rates of severe acute GVHD can be achieved wit hout T cell depletion.