Evaluation of Pre-Collection Factors and Collection Efficiency Leads to Strong Correlation between Predicted and Actual Peripheral Blood Stem Cell Collection Yields in Multiple Myeloma Patients: A Single Institution Experience

Introduction: High dose chemotherapy followed by autologous peripheral blood stem cell (auto-PBSC) transplantation has become the standard therapy for patients with multiple myeloma (MM) and in certain patients with lymphoma. Successful auto-PBSC transplantation depends on the collection of adequate yield of CD34+ cells/kg. However, approximately 10-30% of patients are unable to collect enough hematopoietic stem cells to support high dose chemotherapy and auto-PBSC transplantation. The aim of this study was to investigate the factors associated with CD34+ cell yields in patients with malignancy.

Methods: We retrospectively reviewed all PBSC collection procedures between January 2018 and March 2018. A chart review was performed and the following data collected: age, gender, height, weight, race, diagnosis, disease status before apheresis, complete blood count (CBC) with differential, pre-apheresis CD34+ cell count and ratio, total blood volume processed, CD34+ cell yield/kg, apheresis device, and the device operator. A standardized PBSC mobilization was performed by administration of 6 mg Pegfilgrastim on day 1 and 24 mg plerixafor on day 3. For collections requiring two or three days, an additional 24 mg dose of plerixafor was administered approximately 14 hours prior to each additional collection. Our prediction formula is as follows: [CD34/µL x Volume Process (L) x CE(.43)]/recipient weight (kg). Spearman's correlation and linear regression were applied to assess variable correlation intensity.

Results: A total of 69 procedures were performed on 45 patients with a mean of 1.5 procedures per patient. Successful PBSC mobilization and collection, target was obtained in 39 patients (86.7%) requiring a total of 58 (84.1%) procedures. Administration of 2^nd or 3^rd dose Plerixafor was required in 18 (40%) patients. Patients' demographic data and apheresis collection data are summarized in Table 1 and Table 2 respectively. Linear regression analysis showed a strong correlation (R² = 0.8781) between actual and predicted CD34+ cell yield/kg based on our department benchmark collection efficiency (CE) of 43% determined by the median CE performed on 69 procedures (Figure 1). CD34+ cell yield/kg strongly correlates with pre-apheresis white blood cell (WBC), platelet, neutrophil and CD34+ cell count, post-apheresis WBC and platelet count (p<0.0001) as shown in Table 3. The degree of WBC increase from the pre-collection visit (typically 5-10 days before collection) to collection day (after mobilization) strongly correlates with the pre-apheresis CD34+ cell count and CD34+ cell yield/kg (p<0.0001). CE moderately correlates with pre-apheresis WBC, neutrophil, monocytes, lymphocytes, CD34+ cell count, post-apheresis WBC count, and post-apheresis hemoglobin levels (p<0.05).

Conclusions: Based on our single-institution retrospective experience, our study indicates CD34+ cell yield prediction is excellent after determining institutional specific CE. Comparison of pre-collection day versus collection day lab values can further assist in the predictive model. Lastly, CD34+ cell yields highly correlate with pre-apheresis CD34+ cell counts. Our findings highlight the need for each institution to study pre-collection variables and to determine their CE in order to better predict collection day outcomes.

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