Bi-phasic CD34⁺ cell mobilization of a syngeneic donor during prolonged G-CSF delivery

Background: G-CSF administration over 10 days and neutrophil cytapheresis have been reported in the literature, but the kinetics of CD34⁺ cells in this situation is unclear. Case: A 42-year-old female underwent syngeneic transplantation for metastatic breast cancer. The recipient was in critical condition peri-transplant, therefore the donor received G-CSF for 13 days, during which eight cytaphereses for both PBPC and neutrophils were performed. Two peaks in CD34⁺ cells were noted; the first on Day 5 and the second on Days 10-13 of G-CSF administration; a total of 11.6 × 10⁶/kg CD34⁺ cells and 38.11 × 10⁸/kg neutrophils were infused. The recipient's ANC exceeded 0.1 × 10⁹/L on Day +3. Discussion: To our knowledge, this is the longest reported cytapheresis of CD34⁺ cells from a normal donor. The bi-phasic pattern in the cytapheresis product is also of interest. It is an unusual pattern that suggests a profound and complicated alteration in the marrow progenitor cell pool. If substantiated, this finding may offer an alternative cytapheresis schedule for donors.