Peripheral blood stem cell collection: the interaction of technology, procedure, and biological factors

Centrifugal technology, continuous flow and discontinuous flow, has served as the technology platform for extracting cell concentrates of interest from peripheral blood (PB) for patient therapy for the past 35-40 yr. Models for procedure outcome exist for collection of normal donor (ND) platelet and granulocyte concentrates that integrate: (1) biological variables (pre-procedure PB cell concentration, the total circulating quantity of cells, donor/patient blood volume (BV)), (2) device efficiency, and (3) procedure parameters such as total blood processed (TBP), and in the case of cytoreductions - the volume collected. (cf. Hester J, Kellogg R, Mulzet A, et al., Blood (54) (1979) 254; Hester J, Ventura G, J Clin Apheresis (4) (1988) 188.) To date, no predictive CD34+ yield algorithm integrating these three variables has been formulated that could be applied prospectively for individual ND or patients (PT). There are economic, toxicity and statistical comparison benefits to be derived from generating such an algorithm.A small pilot study is presented with a brief review of current publications that suggest the circulating quantity of CD34+ cells available to be collected and the quantity mobilized during leukapheresis are the major contributing factors to CD34+ yield, somewhat obscuring the role of the total blood processed (TBP). Intraprocedure CD34+ cell mobilization, incompletely characterized to date, appears to be a dynamic nonlinear process, as the harvested yield does not rise proportionally as the fraction of BV processed increases. And, like the pre-procedure PB CD34+ concentration and total circulating quantity, CD34+ mobilization during leukapheresis probably relates to prior treatment and the priming regimen. Studies that provide: (1) separate analyses of PT populations divided according to chemotherapy toxicity factors; (2) design and implementation of optimal priming regimens with respect to dose 'intensity' of both growth factors and chemotherapy; and (3) standardization of laboratory assays of CD34+ enumeration seem essential to generating a predictive algorithm.