Evaluation of the predictive value of the hematopoietic progenitor cell count using an automated hematology analyzer for CD34+ stem cell mobilization and apheresis product yield

Sysmex XN-HPC: study of reference intervals and clinical decision limits in healthy allogeneic donors mobilised with G-CSF

The Sysmex XN series haematopoietic progenitor cell (XN-HPC) is a novel tool for assessing stem cell yield before allogeneic haematopoietic stem cell transplantation. This study aimed to establish a reference interval (RI) for XN-HPC in peripheral blood allogeneic transplant donors following granulocyte colony-stimulating factor (G-CSF) stimulation and determine its clinical significance. All specimens were analysed using Sysmex XN-20. Samples were collected and analysed using non-parametric percentile methods to define the RIs. Quantile regression was used to explore the dependency of the RIs on sex and age. Samples were included in clinical decision limits for apheresis based on receiver operating characteristic curve analysis. The non-parametrically estimated RI for XN-HPC was 623.50 (90% confidence interval [CI90%] 510.00-657.00) to 4,144.28 (CI90% 3,761.00-4,547.00). The RIs for the XN-HPC were not age-dependent but were sex-dependent. The RI for males was 648.40 (CI90% 582.00-709.00)-4,502.60 (CI90% 4,046.00-5,219.00) and for females was 490.90 (CI90% 311.00-652.00)-3,096.90 (CI90% 2,749.00-3,782.00). Comparisons based on XN-HPC values between the poor and less-than-optimal groups, good and less-than-optimal groups, and good and non-good groups had areas under the curve of 0.794 (P < 0.001), 0.768 (P < 0.001), and 0.806 (P < 0.001), respectively, indicating a good predictive value for mobilisation effectiveness. XN-HPC data exceeding 3974 × 106/L suggested that a sufficient number of stem cells could be collected clinically. Values > 5318 < 106/L indicated 100% mobilisation effectiveness. We established an RI for XN-HPC in peripheral blood allogeneic transplant donors following G-CSF stimulation and determined clinical decision thresholds for mobilisation efficiency.

Autologous peripheral blood stem cell harvest timing by absolute neutrophil count in children and young adult patients: Single-institute experience

BACKGROUND

Myeloablative, high-dose chemotherapy followed by autologous peripheral blood stem cell transplantation (PBSCT) improves outcome in some high-risk malignant solid tumors and lymphomas in children and young adults.

METHODS

We performed 16 peripheral blood stem cell (PBSC) harvests in 12 children and 2 young adult patients with a high-risk malignant solid tumor or refractory/relapsed Hodgkin's lymphoma from August 2015 to December 2020. In our chemotherapy mobilization protocol, we used an absolute neutrophil count (ANC) of >1 × 109/L following the nadir after chemotherapy as the criterion for undertaking the apheresis.

RESULTS

The median CD34+ cell count per kg body weight of the 33 apheresis products was 4.92 × 106 cells/kg (range, 0.34-22.53 × 106 cells/kg). Thirteen of the 14 patients (93%) had successful PBSC collections that met their goals for PBSCT. Three patients did not receive PBSCT due to disease progression prior to transplantation. Prompt engraftment occurred in all the remaining 11 patients with 17 PBSCTs.

CONCLUSION

Our data suggest that ANC can be helpful as a surrogate parameter in clinical decision-making when the peripheral blood CD34+ count is unavailable.

Method comparison between hematopoietic progenitor cell and CD34+ cell counts in hematopoietic stem cell collection

BACKGROUND

The reference method for hematopoietic stem cell enumeration is flow cytometric CD34+ cell analysis. We evaluated using the hematopoietic progenitor cell (HPC) count on the Sysmex hematology analyzer to safely replace some flow cytometric measurements performed in peripheral blood samples to guide apheresis timing.

STUDY DESIGN AND METHODS

We compared HPC and CD34+ cell counts in 133 preharvest peripheral blood samples and 124 apheresis products.

RESULTS

Pre-apheresis HPC counts ≥24 × 106/L in healthy donors and ≥36 × 106/L in lymphoma patients predicted adequate mobilization with 100% specificity and positive predictive value, saving 79% and 63% of flow cytometry analyses, respectively. Due to a positive bias (mean bias 50.26; 95% CI 36.24-64.29), a higher threshold was needed in multiple myeloma patients (HPC≥ $$ \ge $$ 132 × 106/L), saving only 24% of flow cytometry analyses.

CONCLUSION

When the HPC count is above the corresponding threshold, apheresis could be safely initiated without waiting for the flow cytometry result, thereby reducing time-to-decision. Lower HPC values, however, require confirmation by flow cytometry.

Hematopoietic Progenitor Cell Counts of the Leukapheresis Product Determined Using Sysmex XN Analyzers Predict a Sufficient Number of CD34+ Stem Cells in a Peripheral Blood Stem Cell Harvest for Autologous Transplantation

Objective Several institutions outsource CD34+ cell counting of leukapheresis products, limiting rapid measurements, as results are obtained the next day. This problem is compounded with plerixafor use, a stem cell-mobilizing drug that increases leukapheresis efficiency but requires administration the day before leukapheresis. Use of this drug for a second leukapheresis procedure before the first-day leukapheresis CD34+ count results are confirmed causes unnecessary leukapheresis and expensive plerixafor administration. We investigated whether or not measuring hematopoietic progenitor cells in leukapheresis products (AP-HPCs) using a Sysmex XN-series analyzer could resolve this problem. Methods We retrospectively compared the absolute AP-HPC value per body weight with the CD34+ (AP-CD34+) count in 96 first-day leukapheresis product samples obtained between September 2013 and January 2021. Comparisons were also conducted according to regimen: granulocyte colony-stimulating factor (G-CSF) monotherapy, chemotherapy plus G-CSF, or plerixafor mobilization. Results AP-CD34+ and AP-HPC counts correlated strongly (rs=0.846) overall and, in particular, under chemotherapy plus G-CSF (rs=0.92) but correlated mildly under G-CSF monotherapy (rs=0.655). AP-HPCs could not completely be dichotomized based on an AP-CD34+ threshold of 2×106/kg for any stimulation procedure. In most cases with AP-HPCs >6×106/kg, the AP-CD34+ count exceeded 2.0×106/kg, but in 5.7% of these cases, the AP-CD34+ count was <2.0×106/kg. A cut-off of AP-HPCs >4.843×106/kg yielded a sensitivity of 71% and specificity of 96% for predicting AP-CD34+≥2×106/kg. Conclusion AP-HPCs can identify cases in which sufficient stem cells have been collected.

Non-interventional Study Evaluating the Mobilization of Stem Cells by Plerixafor Before Salvage Autologous Stem Cell Transplant in Relapsed Multiple Myeloma (IFM-2015-03)

INTRODUCTION

Despite the implementation of new therapeutic agents, management of relapsed multiple myeloma (MM) remains a challenge. Salvage autologous hematopoietic cell transplant (AHCT) remains a valid therapeutic option for eligible patients who achieve prolonged response after a first AHCT. However, a second graft is not always available, and these patients may need a second mobilization.

PATIENTS AND METHODS

This prospective, non-interventional, multicenter study aimed to collect data on the feasibility of salvage AHCT using a plerixafor-based hematopoietic cell mobilization in relapsed MM, according to the plerixafor label in France. Adult patients with relapsed MM eligible for a second AHCT and mobilized using granulocyte- colony stimulating factor (G-CSF) and plerixafor were included.

RESULTS

Of the 23 patients, 17 achieved a successful hematopoietic cell mobilization and 13 were able to proceed to a second AHCT. Median age was 62.9 years (min-max 51-71). Ten patients (77%) were male. Eleven (85%) received AHCT as a third-line treatment or more. Median time between first and second AHCT was 5.4 years (range, 2.6-16.3). Among 18 evaluable patients, mobilization was successful for 17 (94%) of them [95% CI 84-100], with no reported side effects. Among the 13 patients who underwent salvage AHCT, the median time to engraftment was 14 days (min-max 11-29). One-year progression-free and overall survival were 88.9% [95% CI 43.3-98.4] and 100%, respectively.

CONCLUSION

This study demonstrated that plerixafor allows safe and efficient mobilization in relapsed MM patients who are candidates for a salvage AHCT.

TRIAL REGISTRATION

NCT02439476 Registered 8 May 2015, https://clinicaltrials.gov/ct2/show/NCT02439476 .

Correlation between peripheral blood automated hematopoietic progenitor cell counts and flow cytometric CD34+ cell counts differs according to diagnosis in patients undergoing autologous peripheral blood stem cell transplantation

BACKGROUND

An automated hematopoietic progenitor cell count measurement in Sysmex XN analyzer (XN-HPC) has been developed to assist flow cytometry CD34⁺ cell count measurement, which requires technical expertise and a long turnaround time. Here, we evaluated the correlation between XN-HPC count and flow cytometric CD34⁺ cell count in pre-harvest peripheral blood (PB) samples from patients undergoing autologous peripheral blood stem cell (PBSC) transplantation according to diagnosis and investigated the possible cause of the decreased correlation in plasma cell neoplasm patients.

MATERIALS AND METHODS

We retrospectively included 399 patient data that had matched PB XN-HPC count and CD34⁺ cell count of PB and apheresis product from Samsung Medical Center (SMC) and the Hematopoietic Stem Cell (HSC) registry. We assessed the diagnostic accuracy and the potential cutoff values of XN-HPC count for predicting adequate PBSC collection.

RESULTS

The PB XN-HPC count was 1.6 and 1.3-fold higher than the CD34⁺ cell count in SMC (25.0 vs 15.9/μl) and the HSC registry (20.0 vs 15.2/μl), respectively. Overall the correlation between the PB XN-HPC and CD34⁺ cell count was moderate (SMC, r = 0.71; HSC registry, r = 0.66). A significant proportional and systemic bias with overestimation of XN-HPC count were noted in the plasma cell neoplasm patients in both SMC and the HSC registry. However, no significant difference in correlation was observed according to myeloma-related laboratory parameters in plasma cell neoplasm patients.

CONCLUSION

Our results suggest that XN-HPC count should be interpreted cautiously in cancer patients undergoing autologous PBSC transplantation, especially in those with plasma cell neoplasm.

Usefulness of hematopoietic progenitor cell monitoring to predict autologous peripheral blood stem cell harvest timing: A single-center retrospective study

INTRODUCTION

In autologous peripheral blood stem cell harvest (APBSCH), CD34-positive cells have been measured to assess the numbers of hematopoietic stem cells, but measurement requires specialized equipment. Recently, there was a report that peripheral blood hematopoietic progenitor cells (HPCs) are useful indicators of the presence of hematopoietic stem cells. We examined the usefulness of HPC monitoring to predict APBSCH timing.

METHODS

We retrospectively analyzed the relationship between HPC and collected CD34-positive cells in 84 consecutive patients who underwent APBSCH.

RESULTS

According to the receiver operating characteristics curve for the collection of ≥2 × 106 CD34-positive cells/kg, the HPC cut-off value on the day before collection was 21/μL, while that on the day of collection was 41/μL. No significant factors were found in the univariate analysis except for the HPC count on the day before collection (p < 0.001) and the day of collection (p < 0.001). According to the multivariate analysis, the HPC count on the day before collection (p < 0.001) and the day of collection (p < 0.001) were also factors that strongly influenced the quantity of CD34-positive cells collected.

CONCLUSION

Our results suggest that the HPC count on not only the day of collection but also the day before collection is a good indicator for appropriate APBSCH timing.

A study to compare Hematopoietic Progenitor Cell count determined on a next-generation automated cell counter with flow cytometric CD34 count in peripheral blood and the harvested peripheral blood stem cell graft from autologous and allogenic donors

INTRODUCTION

A successful bone marrow transplant requires a minimum of 2-4 × 10⁶ cells/kg patient body weight of CD 34+ cells to be transfused, where peripheral blood CD34+ cell count being and ideal predictor. We compared the correlation and predictive capacity of both hematopoietic progenitor cell count (HPC) determined on the Sysmex XN-9000 and flow cytometric CD34 in autologous and allogenic donors.

METHODS

Autologous and allogenic donors were taken as per criteria. TLC (Total Leukocyte Count), MNC (Mononuclear cell count), HPC, and CD34 assay were done in both the peripheral blood prior to apheresis, and the harvest product postapheresis. Sysmex XN-9000 was used for TLC, MNC, and HPC tests, and a modified ISH-AGE protocol was used to enumerate CD34 by flow cytometry. Statistical analysis was done using SPSS 16.0.

RESULTS

Sixty-seven allogenic and 35 autologous donors were enrolled. 45% were females, and 55% were males. Correlation between HPC and CD34 was found to be 0.887 with P value < .01 in peripheral blood and 0.847 with P value < .01 in the harvested product. On the other hand, TLC had a correlation of 0.424 and 0.520 in peripheral blood and harvested, respectively. MNC had a weak association. The cutoff value for a target dose of 2 × 10⁶ CD34 cells/kg was 37 × 10⁶ /L for pre-HPC. For a target of 4 × 10⁶ CD34 cells/kg, the cutoff value calculated to be 54 × 10⁶ /L (Sensitivity: 85%, Specificity: 89%) for peripheral blood HPC.

CONCLUSION

We conclude that HPC is comparable to CD34 in predicting harvest product's adequacy.

Cost and efficacy of peripheral stem cell mobilization strategies in multiple myeloma

Mobilization of peripheral blood stem cells (PBSC) can be performed using plerixafor, which is expensive, or high-dose cyclophosphamide (HDCy). We hypothesized that the overall cost of mobilization with plerixafor might not be greater if the cost of complication management was considered. We performed a cost analysis of these two strategies. This multicentric observational study recruited patients with myeloma who underwent a first PBSC mobilization. We considered direct medical costs, including hospitalization, mobilization agents, apheresis, and supportive treatments. We included 111 patients, 54 and 57 in the HDCy and plerixafor groups, respectively. Cost of mobilization with HDCy was 5097 ± 2982€ vs. 10958 ± 1789€ for plerixafor (p < 0.0001). Cost of agents used was 1287 ± 779€ vs. 6552 ± 509€, respectively (p = 0.0009). The mean number of days of hospitalization was 2 and 2.1 days, respectively (p = 0.035). All patients achieved the minimum PBSC collection target (p = 1.0); however, ASCT was performed with HDCy in 67% patients and with plerixafor in 86% (p = 0.02). Plerixafor mobilization incurred a greater cost, mostly due to the greater cost of the drug. Hospitalization length in the two groups was similar in our series. Interestingly, plerixafor appeared to be a very effective and safe mobilizing approach translating into a greater ASCT success.