Large Volume Leukapheresis for Collecting Hemopoietic Progenitors: Role of CD 34+ Precount in Predicting Successful Collection

Abstract

In this work we evaluated the efficacy of stem cell collection with Large Volume Procedures. (LVP), and analysed the importance of the CD34+ cell precount in promoting the collection of a sufficient number of CD34+ cells for transplantation, using the Univariate Logistic Regression analysis. Eighty-nine leukapheresis were performed in 49 patients with hematological malignancies and solid tumors, mobilized with chemotherapy plus Granulocyte Colony Stimulating Factor (G-CSF). For each procedure 15.8 liters of blood were processed. The median value of Nucleated Cells (NC) and CD34+ cells precount was respectively 8.29 × 10⁹/ml (range 1.13÷45.4) and 43.08 × 103/ml (range 1.06÷795.2). Results show the capability of LVP to collect large quantities of hemopoietic progenitors with a median CD34+ cell total yield of 215.02 × 10⁶ (range 5.03÷2210). The yields per patients’ body weight were: CD34+ cells 3.23 × 10⁶/kg (range 0.081÷41.58). The regression analysis between blood cell precounts and collection yields gave the following correlations: the CD34+ cell precount correlates with CD34+ yield (r = 0.78 p < 0.00) and with CD34+ cell yield/kg (r = 0.76 p < 0.00). The number of CD34+ cells processed correlated with the number of CD34+ cells collected/kg (r = 0.83 p < 0.000). To investigate the importance of CD 34+ cell precount in promoting CD34+ cell yields ≥2.5 × 10⁶/kg we performed a Univariate Logistic Regression analysis that showed in our patients a probability of collecting ≥2.5 × 10⁶ CD34+/kg that rose from 0.6 to 0.95 for CD 34+ precounts that oscillated from 30 to 40 × 10³ CD34+ cells/ml, respectively. The Univariate Logistic Regression gave a probability of collecting ≥2.5 × 10⁶ CD34+ cells/kg that oscillated between 0.64÷0.98 for values of CD34+ cells processed from 6 × 10⁶/kg to 8 × 10⁶/kg, p <0.000. Sixty-three percent of patients reached the target dose of 2.5 × 10⁶ CD34+ cells/kg with only one LVP. Until now 12 patients have been transplanted and all have had a prompt and complete lasting recovery. These results confirm the efficacy of LVP in harvesting hemopoietic progenitors and their ability in reconstituting hemopoiesis of transplanted patients, enabling the estimation of CD34+ precounts and CD34+ cells processed values, highly predictive for the collection of ≥2.5 × 10⁶ CD34+ cells/kg. Furthermore, the Logistic Model suggests that the best strategy to plan a successful CD34+ cell collection procedure is to identify for each patient the amount of CD34+ cells/kg to be processed rather than the fixed processing of 3÷5 blood volumes in all patients.