Blood CD34 Levels as a Predictor of Successful Peripheral Blood Stem Cell Mobilization In Consecutive Autologous Stem Cell Apheresis Patients From a Single Transplant Center

The optimal strategy to mobilize hematopoietic stem cells into peripheral blood for collection has not been defined, and some patients do not successfully mobilize. Failure to harvest the desired number of CD34+ cells results in emotional disappointment for the patient and ineffective utilization of resources. In this study we analyzed various factors influencing CD34+ yields during stem cell collection in patients being considered for autologous transplantation whose peripheral blood CD34+ analysis triggered stem cell collection (usually >10/μ L), and we determined thresholds for successful collection in a single apheresis session.

Retrospective chart review of 244 consecutive patients who underwent stem cell collection at the University of Rochester between 2005 and 2008 was conducted. Cells were collected via Cobe semi-automated protocols. For each of the patients, diagnosis, age, gender, type of infusion, marrow status, number of prior chemotherapy treatments, mobilization regimen, CD34+ count/μ l on first day, CD34+/kg after first apheresis, total time of apheresis and volume processed (liters) were recorded. The various mobilization regimens utilized were 1)GCSF, 2)CHEMO (salvage therapy with DHAP, ESHAP, RICE) with GCSF, 3)cyclophosphamide with GCSF, 4)AMD3100 (Plerixafor) with GCSF, and 5) GCSF with GMCSF. The marrow status was defined as no involvement, mild involvement (10-20%), and moderate involvement (>20%). Another factor considered was the number of prior chemotherapy regimens, and the total number of apheresis cycles required to reach targeted yields was recorded. All statistical analyses were conducted using SAS 9.2. All tests were two-sided with p-values ≤ 0.05 considered significant.

Analysis revealed a positive linear relationship between the log of initial CD34+ counts and the log transformed number of CD34+ cells/kg on the first day of apheresis (R²= 0.57, p < 0.001). Multivariate analysis suggested that both CD34+ count per μ L blood prior to first apheresis (p < 0.001) and time on the machine (p = 0.08) were positively associated with CD34+ end yield after adjusting for age and gender. A similar analysis on all the mobilization regimens revealed statistical significance for a higher initial CD34 cell count/μ l predicting a higher apheresis yield (p < 0.001). Also, for each of the major diagnoses (AL, HL, MM. NHL), there was a positive relationship between peripheral CD34+ cells/μ l prior to apheresis and CD34+ cells/kg after first apheresis yield (p < 0.001) Another objective of this study was to see if there is a threshold number of CD34+ cells/μ l blood that would predict for lymphoma patients (combined HL, NHL) that at least 4 × 10⁶ CD34+ cells/kg would be reached on the first day of apheresis, and a similar threshold for the multiple myeloma patients (MM) to reach 6 × 10⁶ CD34+ cells/kg on first day. Receiver operating characteristics (ROC) curves were used to determine an optimal initial CD34+ count cutoff and the odds ratio of achieving such a threshold between the two groups was assessed using logistic regressions. Based on the cutoff of 48.3 cells/μ L, lymphoma patients were classified into two groups depending on their initial CD34+ count greater or less than this cutoff. The odds of reaching at least 4 × 10⁶ CD34+ cells/kg on the first day of apheresis when the initial CD34+ count was greater than 48.3 cells/μ L were 24.4 times than those with the initial CD34+ count less than the cutoff (p<0.001). Similarly, for multiple myeloma patients, to reach a threshold of 6×10⁶ CD34+ cells/kg on the first day of apheresis, a cutoff of 90.5 cells/μ L was established. The odds of reaching at least 6×10⁶ CD34+ cells/kg on the first day of apheresis with initial CD34+ count greater than 90.5 cells/μ L were 19.3 times than those with initial CD34+ count less than the cutoff (p<0.001)

This study confirmed that the initial peripheral CD34+ count was a good predictor of the CD34+ cells/kg yield on the first day of apheresis, irrespective of disease type or mobilization regimen utilized. A threshold of 48.3 CD34+ cells/μ L for lymphoma patients and 90.5 CD34+ cells/μ L for myeloma patients was established to reach goals of least 4 × 10⁶ CD34+ cells/kg and 6 × 10⁶ CD34+ cells/kg respectively with a single apheresis. These thresholds or others calculated similarly for other collection goals could potentially aid in coordination of apheresis resource utilization.

No relevant conflicts of interest to declare.