Kinetics of standardized large volume leukapheresis (LVL) in patients do not show a recruitment phenomenon of peripheral blood progenitor cells (PBPC)

Although several studies have demonstrated the efficacy of large volume leu kapheresis (LVL) to yield high numbers of peripheral blood progenitor cells (PBPC), the mechanisms of stem cell release into circulation and the postu lated phenomenon of PBPC recruitment during apheresis have not been investi gated in detail. Therefore, we analyzed the kinetics of stem cell enrichmen t in a total of 34 standardized LVL for patients with hematologic malignanc ies (lymphoma, multiple myeloma) and solid tumors (breast cancer, rhabdomyo sarcoma). LVL was started 2 h after administration of G-CSF processing six times the patient's blood volume. Cells were sequentially collected into si x bags and the numbers of leukocytes, mononuclear cells (MNC), CD34(+) cell s and colony-forming cells (CFU-GM) in each collection bag were analyzed. T he numbers of PBPC collected demonstrated a continuous decrease starting af ter an early maximum during the second processed blood volume (P = 0.001). Interestingly, these kinetics of decreasing stem cell yields during LVL wer e similar for both entities of patients with hematologic malignancies as we ll as for both groups of patients with solid tumors. In summary, a recruitm ent phenomenon, defined as a time-dependent and LVL-induced increase of PBP C, could not be demonstrated in any of the diseases investigated.