AN ANALYSIS OF ENGRAFTMENT KINETICS AS A FUNCTION OF THE CD34 CONTENTOF PERIPHERAL-BLOOD PROGENITOR-CELL COLLECTIONS IN 692 PATIENTS AFTERTHE ADMINISTRATION OF MYELOABLATIVE CHEMOTHERAPY

The CD34 antigen is expressed by committed and uncommitted hematopoiet ic progenitor cells and is increasingly used to assess stem cell conte nt of peripheral blood progenitor cell (PBPC) collections, Quantitativ e CD34 expression in PBPC collections has been suggested to correlate with engraftment kinetics of PBPCs infused after myeloablative therapy . We analyzed the engraftment kinetics as a function of CD34 content i n 692 patients treated with high-dose chemotherapy (HDC). Patients had PBPCs collected after cyclophosphamide based mobilization chemotherap y with or without recombinant human granulocyte colony-stimulating fac tor (rhG-CSF) until greater than or equal to 2.5 x 10(6) CD34(+) cells /kg were harvested, Measurement of the CD34 content of PBPC collection s was performed daily by a central reference laboratory using a single technique of CD34 analysis, Forty-five patients required a second mob ilization procedure to achieve greater than or equal to 2.5 x 10(6) CD 34(+) cells/kg and 15 patients with less than 2.5 x 10(6) CD34(+) cell s/kg available for infusion received HDC. A median of 9.94 x 10(6) CD3 4(+) cells/kg (range, 0.5 to 112.6 x 106 CD34(+) cells/kg) contained i n the PBPC collections was subsequently infused into patients after th e administration of HDC. Engraftment was rapid with patients requiring a median of 9 days (range, 5 to 38 days) to achieve a neutrophil coun t of 0.5 x 10(9)/L and a median of 9 days (range, 4 to 53+ days) to ac hieve a platelet count of greater than or equal to 20 x 10(9)/L. A cle ar dose-response relationship was evident between the number of CD34() cells per kilogram infused and neutrophil and platelet engraftment k inetics. Factors potentially influencing the engraftment kinetics of n eutrophil and platelet recovery were examined using a Cox regression m odel. The single most powerful mediator of both platelet (P = .0001) a nd neutrophil (P = .0001) recovery was the CD34 content of the PBPC pr oduct. Administration of a post-PBPC infusion myeloid growth factor wa s also highly correlated with neutrophil recovery (P = .0001). Patient s receiving high-dose cyclophosphamide, thiotepa, and carboplatin had more rapid platelet recovery than patients receiving other regimens (P = .006), and patients requiring 2 mobilization procedures versus 1 mo bilization procedure to achieve greater than or equal to 2.5 x 10(6) C D34(+) cells/kg experienced slower platelet recovery (P = .005). Altho ugh a minimal threshold CD34 dose could not be defined, greater than o r equal to 5.0 x 10(6) CD34(+) cells/kg appears to be optimal for ensu ring rapid neutrophil and platelet recovery. (C) 1995 by The American Society of Hematology.