The CD34+ Cell Dose Matters in Hematopoietic Stem Cell Transplantation with Sibling Donors Receiving Peripheral Blood Stem-Cells.

The outcome of allogeneic hematopoietic stem cell transplantation (HSCT) is influenced by many factors (underlying disease, HLA-matching, patient and donor age, CMV serostatus, co-morbidities, conditioning regimen, GVHD prophylaxis and graft source and composition). The number of T-cells contained in the graft is associated with the incidence and severity of GvHD. The effect of CD34+ cell dose in HSCT on overall survival and incidence of acute and chronic GvHD is less well established. We analyzed transplant outcomes in 189 patients with hematological malignancy and sibling donor receiving G-CSF mobilized peripheral blood stem cell grafts. Myeloablative conditioning was given to 88 patients and reduced intensity conditioning to 101 patients. Median CD34+ cell dose was 5.6 × 106/kg (0.6-17.0). Anti-thymocyte globulin (ATG) was not given. Median time to neutrophil engraftment (ANC >0.5 × 109/L) was 17 days. In multivariate analysis <5 × 106/CD34+ cells/kg correlated to slower engraftment, measured as later than median days-to-engraftment (OR 2.62, 95% CI 1.27-5.41, p=0.008). The 5-year overall survival (OS) for all patients was 47%. The best 5-year OS (71%) was seen in patients receiving 6-7 × 106CD34+cells/kg (HR: 0.43, 95% CI: 0.24-0.78, p=0.005) (fig 1). Transplant related mortality at 1 and 5 years was 19% and 28%, respectively. The lowest TRM (15%) was found among patients given a CD34+ cell dose of 6-7 × 106cells/kg (HR: 0.41, 95% CI: 0.18-0.92, p=0.03). The cumulative incidence of relapse (RI) for all patients was 29%. Increased RI (41%) was found in patients who received <5 × 106cells/kg CD34+ cells (HR: 1.89, 95% CI: 1.09-3.29, p=0.024). In total, 86 (46%) and 92 (56%) patients developed acute and chronic GvHD, respectively. The cumulative incidence of acute GVHD grades II-IV in the whole cohort was 40%. The lowest incidence (33%) of aGVHD II-IV was found among patients receiving a high cell-dose. In the corrected multivariate analysis, a CD34+ cell dose of >6.5 × 106cells/kg was associated with a lower incidence of aGVHD II-IV (RH: 0. 53, 95% CI: 0.29-0.97, p=0.04). In the corrected multivariate analysis a CD34 cell dose of 6-7 × 106/kg was associated with better OS and lower TRM, while a CD34 cell-dose of <5 × 106/kg was associated with more relapse and less cGVHD. A high CD34 cell-dose (>7 × 106/kg) correlated to less aGVHD II-IV. The CD34 cell dose has impact on the outcome in sibling donor HSCT using peripheral-blood stem-cells. [ABSTRACT FROM AUTHOR]