Can We Predict the Number of Circulating CD34+ Cells From the Complete Blood Cell Count Before and After Plerixafor in Patients With Lymphoproliferative Disorders?

Abstract Stem cell transplant is a common treatment for hematopoietic neoplasms. We use a standardized stem cell mobilization regimen consisting of the following: day 1, 6 mg of pegfilgrastim (pegylated formulation of granulocyte-colony stimulating factor); day 3, 24 mg of plerixafor (reversible CXCR4 antagonist) followed by peripheral blood stem cell collection (PBSC) on day 4 after collecting a sample to measure the circulating CD34+ cells by flow cytometry. Since the latter results are not available as quickly as a STAT complete blood count (CBC), we hypothesized that the difference in CBC parameters from DAY 3 TO DAY 4 could be useful to predict the final collection yield. To test our theory, we carried out the following process from September 2018 to February 2019: day 3, CBC with differential before plerixafor; day 4, CBC with differential and sample for CD34+ cells before starting PBSC. We collected the following data from the electronic medical records: gender, age, and CBC parameters preplerixafor (evening of day 3) and morning of day 4 (preapheresis) plus circulating CD34+ count. We used a paired Student t test to compare the results of each patient. Fifty-seven adults (35 males, 22 females) with a median age of 64 ± 13 years were included; 76% had the diagnosis of multiple myeloma. On day 3 (preplerixafor), the median hematocrit was 36 ± 8%, the WBC count was 29 ± 13 × 103/µL, and the platelet count was 189 ± 64 × 103/µL. On the next morning (day 4), the hematocrit and platelet counts were not significantly different at 36 ± 4% and 182 ± 60 × 103/µL, respectively (P > .05). However, the median WBC count was significantly higher with a median of 43 ± 16 × 103/µL (P = 2.5 × 10–20). In both CBCs with differential, neutrophils comprised the majority at 82% and 74% pre- and postplerixafor, respectively (P = .01), lymphocytes went from 7% to 8% (P > .05), and monocytes increased from 6% to 6.5% (P = .02). The median CD34+ count preapheresis was 40 ± 47 cells/µL. We did not find any strong correlation between day 3 and day 4 CBC parameters and the CD34+ count, with only a very weak trend for higher CD34+ cells with increasing day 4 WBC count (R2 = 0.225). We conclude that the precollection CD34+ cell count is the best way to predict the PBSC yield and must be performed in order to ensure the target number of CD34+ cells is met for a successful engraftment.