Subsets of CD34(+) hematopoietic progenitors and platelet recovery after high dose chemotherapy and peripheral blood stem cell transplantation

Background and Objective. Randomized clinical trials have shown that periph eral blood stem cell transplantations (PBSCT) with appropriate doses of CD3 4(+) cells are associated with rapid, complete and sustained recovery of ma rrow functions. Nevertheless, in a minority af patients delayed platelet re covery may occur and it remains to be established whether analysis of trans planted CD34(+) cell subsets may demonstrate correlation with this phenomen on. We studied a series of 80 consecutive transplanted patients with the ai m of evaluating the effect of CD34(+) stem cell numbers and, in a subgroup of 32 patients, the effect of the lineage specific subset numbers on time t o platelet engraftment (i.e. time to platelet counts higher than 20x10(9)/L for two consecutive days without the need for platelet transfusions). Design and Methods. Different clinical and paraclinical factors were examin ed in a multivariate analysis for effect on platelet engraftment in 80 pati ents. Results. The number of CD34(+) cells/kg infused was the most important fact or predicting the time to platelet engraftment. Patients receiving more tha n 10x10(6) CD34(+) cells/kg had prompt platelet engraftment. The majority o f the patients (78%) received fewer than 10x106 CD34(+) cells/kg and 17/62 (27%) of these patients experienced delayed platelet engraftment. In 32 pat ients receiving fewer than 10x106 CD34(+) cells/kg we focused on the conten t of different lineage specific CD34(+) subsets in the PBSC products. The m ost significant correlation was recognized for CD34(+)/CD61(+) megakaryocyt ic cell number and platelet engraftment. An inverse correlation between the CD34(+)/CD38(-) subset and platelet engraftment was found, indicating that a high number of CD34(+)/CD38(-) in the PBSC product might increase the ri sk for delayed engraftment. These results were further confirmed by the obs ervation that patients who experienced platelet engraftment after day 20 ha d significantly more CD34(+)/CD38(-) cells/kg infused than patients with fa st engraftment. Interpretation and Conclusions. The number of total CD34+ cells/kg infused was the most important factor predicting time to platelet engraftment. CD34 (+) subset analysis in a subgroup of patients suggests that a high number o f uncommitted progenitors may be associated with slower platelet recovery t han transplantation with a higher fraction of more committed peripheral blo od stem cells. (C) 1999, Ferrata Storti Foundation.