CD34+cell dose predicts relapse and survival after T-cell-depleted HLA-identical haematopoietic stem cell transplantation (HSCT) for haematological malignancies

Seventy-eight patients with haematological malignancies, received T-cell-de pleted stem cell transplants and cyclosporin followed by delayed add-back, of donor lymphocytes to prevent leukaemia relapse. The source of stem cells was bone marrow in 50 patients and granulocyte colony-stimulating factor ( G-CSF)-mobilized peripheral blood in 28 patients. In univariate analysis, o nly the CD34+ cell dose (but not the stem cell source or the T lymphocyte d ose) and disease status were predictive for transplant-related mortality, r elapse and survival. Patients receiving greater than or equal to 3 x 10(6) CD34+ cells/kg had an overall actuarial survival of 68% compared with 52%, 35% and 10%, respectively, for cell doses of 2-2.99, 1-1.99 and < 1 x 10(6) /kg, Multivariate analysis of risk factors for relapse identified disease r isk and CD34+ cell dose as the only factors. Relapse was 62.5% in 38 patien ts at high risk of relapse vs, 25% for 40 patients at intermediate or low r isk, CD34+ cell doses of greater than or equal to 3 x 10(6)/kg were associa ted with a 13.5% relapse vs. 48% for recipients of lower doses. This favour able effect of CD34+ cell dose on relapse was apparent in both high- and in termediate- plus low-risk groups. Our results support the potential benefit of a high stem cell dose in lowering transplant-related mortality (TRM) an d in reducing relapse after allogeneic marrow or blood stem cell transplant s.