High CD34+ cell dose promotes faster platelet recovery after autologous stem cell transplantation for acute myeloid leukemia.

We studied platelet engraftment in 58 patients with acute myeloid leukemia in first remission treated with autologous stem cell transplantation (ASCT) to determine whether CD34+ cell doses >10 x 10(6)/kg were associated with faster platelet engraftment. We compared engraftment rates in patients receiving CD34+ doses between 5 and 10 x 10(6)/kg (standard-dose ASCT) with those receiving doses > or =10 x 10(6)/kg (high-dose [HD] ASCT). We also studied neutrophil engraftment rates and platelet and red blood cell transfusion requirements. In multivariate adjusted models, the rate of platelet recovery to > or =20,000/microL was 4-fold greater among subjects who received HD-ASCT (hazard ratio [HR], 4.1; confidence interval [CI], 1.8-9.2; P =.001), with median recovery times of 14 versus 28 days. The rate of platelet recovery to > or =50,000/microL was 2-fold greater (HR, 2.1; CI, 1.3-5.9; P =.01), with median recovery times of 19 versus 46 days. Faster platelet recovery resulted in the need for fewer platelet transfusions among the subjects who received HD-ASCT (mean transfusions, 3.7 versus 9.8; P =.005). Although not statistically significant, neutrophil recovery data in the adjusted model suggested a similar effect in the HD-ASCT group, with faster engraftment times at absolute neutrophil counts >500/microL (median, 9.2 versus 12 days; HR, 1.6; CI, 0.69-3.5; P =.29) and absolute neutrophil counts >1000/microL (median, 9.5 versus 12 days; HR, 1.3; CI, 0.56-2.8; P =.58). Subjects who received HD-ASCT required fewer red blood cell transfusions (4.0 versus 9.8 units; P =.01). Our findings suggest that CD34+ cell doses >10 x 10(6)/kg CD34+ result in faster engraftment and fewer red blood cell and platelet transfusions.