Impact of a Low CD34+ Cell Dose on Allogeneic Peripheral Blood Stem Cell Transplantation

Although the CD34⁺ cell dose in allogeneic peripheral blood stem cell transplantation (PBSCT) is considered to be associated with transplantation outcomes, a lower acceptable threshold has not been defined. We retrospectively analyzed 2919 adult patients with hematologic malignancies who underwent related PBSCT in Japan between 2001 and 2014. According to the number of CD34⁺ cells in the graft, we categorized 2494 patients in the standard group (2 to 5 × 10⁶ cells/kg), 377 patient in the low group (1 to 2?×?10⁶ cells/kg), and 48 patients in the very low group (<1?×?10⁶ cells/kg). Compared with the standard group, the low and very low groups showed delayed neutrophil recovery (93.8%, 89.5%, and 78.3%, respectively at day +28; P?P?+ cell doses of 1 to 2?×?10⁶ cells/kg gives acceptable results, whereas further investigations are needed to evaluate the effects of lower doses of <1?×?10⁶ cells/kg owing to the smaller number and the higher percentage of patients with adverse prognostic factors in this cohort.