Factors predicting engraftment of autologous blood stem cells: CD34⁺ subsets inferior to the total CD34⁺ cell dose

Abstract

Data were analyzed on 178 consecutive patients (median age 43 years) who underwent autologous blood stem cell transplantation (ABSCT) at a single institution to determine if CD34⁺subsets (CD34⁺38⁻, CD34⁺33⁻, CD34⁺33⁺, CD34⁺41⁺) or various clinical factors affect hematopoietic engraftment independent of the total CD34⁺ cell dose/kg. Using Cox proportional hazards models, the factors independently associated with rapid neutrophil engraftment were higher CD34⁺ dose/kg, use of G-CSF post-ABSCT, and conditioning regimen (single-agent melphalan ± TBI slower). Factors independently associated with rapid platelet engraftment were higher CD34⁺ cell dose/kg, higher ratio of CD34⁺33⁻/total CD34⁺ cells infused, conditioning regimen (mitoxantrone, vinblastine, cyclophosphamide faster), and no CD34⁺ cell selection of the autograft. The CD34⁺ cell selection process seemed to deplete CD34⁺41⁺ cells to a greater extent than total CD34⁺cells which may explain our observation that it resulted in slower platelet engraftment. In conclusion, the total CD34⁺ dose/kg was a better predictor of hematopoietic engraftment following ABSCT than the dose of any CD34⁺ subset. Platelet engraftment, however, was also influenced by the ratio of CD34⁺33⁻/total CD34⁺cells for unmanipulated autografts, and possibly by the CD34⁺41⁺dose for autografts manipulated by CD34⁺ selection. The use of CD34⁺ subsets requires further investigation in predicting engraftment of autografts which undergo ex vivo manipulation.