Catastrophic CD34+ autologous hematopoietic stem cell collection despite sustained mobilization and solutions to rescue the harvests.

Abstract

Poor collection of hematopoietic stem cells during insufficient mobilization for autologous stem cell transplantation has been widely described. However, only isolated cases of insufficient stem cell collection despite adequate mobilization prior to autologous transplantation have been reported. Over a 5-year period, French apheresis teams reported 31 cases of highly disastrous HSC collection (1.0±0.9 × 10⁶ CD34+ cells/kg, median 0.65) (using a continuous collection method), despite adequate levels of circulating CD34+ cells (79 ± 49/μL, median 79/μL) during the processing of 3 blood volumes. Collection efficiency is the main indicator for assessing the ability to collect cells during cytapheresis. These collections were characterized by disastrous collection efficiencies (CE₂), considered very low below 20% (8/31 patients) and catastrophic below 10% (23/31 patients). The teams attempted to find solutions to compensate for these disastrous and unexpected collections. Changes to the collection parameters led only to minor improvements in collection efficiency (CE₂=8 ± 5 vs 5 ± 2%) and the amount of hematopoietic stem cells collected (1.46 ± 1.39 vs 0.56 ± 0.45 × 10⁶ CD34+ cells/kg), while switching from a continuous collection technique to a discontinuous technique resulted in a significant improvement in collection efficiencies (39 ± 20 vs 8 ± 6%) and the amount of hematopoietic stem cells collected (4.64 ± 3.39 vs 1.09 ± 0.88 × 10⁶ CD34+ cells/kg). Our work highlights the importance of switching from a continuous collection technique to a discontinuous technique in cases of catastrophic collection despite appropriate hematopoietic stem cell mobilization.