Effective chemomobilization with etoposide and cytarabine (EC regimen) in lymphoma patients: a single-center, retrospective, observational study

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.

Etoposide + Granulocyte Colony-Stimulating Factor and Optional Plerixafor in Patients Who Failed Chemomobilization with or without Plerixafor

We conducted a retrospective study of 62 patients undergoing etoposide (2 g/m²) + granulocyte colony-stimulating factor (G-CSF; 10 patients also received additional plerixafor) as a salvage stem cell mobilization regimen after previous unsuccessful chemomobilization with or without plerixafor. The median peak CD34⁺ values after etoposide + G-CSF ± plerixafor was 54.07 CD34⁺/μL compared with 9.6 CD34⁺/μL after previous mobilization attempts (P < .001). The median yield was 6.33 × 10⁶ CD34⁺ cells/kg per 2 apheresis. Etoposide + G-CSF ± plerixafor mobilization regimen resulted in 91.53% successful mobilizations and 89.83% of patients proceeding to autologous stem cell transplantation. All 7 patients who had previously failed plerixafor-based mobilization attempts were successfully mobilized with etoposide + G-CSF ± plerixafor and proceeded to autologous stem cell transplantation. The most common grades 3 to 4 adverse events of etoposide + G-CSF ± plerixafor were febrile neutropenia (69.35%), mucositis (51.62%), and bacteremia (20.97%). No fatal outcomes were observed. Rates of 12-month overall survival and progression-free survival were 88.71% and 70.97%, respectively. Etoposide + G-CSF ± plerixafor is an effective regimen for salvage stem cell mobilization also in patients who failed plerixafor, with most patients undergoing autologous stem cell transplantation. The adverse event rate may warrant a decrease in the dose of etoposide.