Effect of CD34+ Selection and Various Schedules of Stem Cell Reinfusion and Granulocyte Colony-Stimulating Factor Priming on Hematopoietic Recovery After High-Dose Chemotherapy for Breast Cancer

Abstract

We evaluated the effects of various schedules of peripheral blood stem cell (PBSC) reinfusion, granulocyte colony-stimulating factor (G-CSF ) priming, and CD34+ enrichment on hematopoietic recovery in 88 patients with advanced breast cancer treated with high-dose chemotherapy, consisting of cisplatin 250 mg/m2, etoposide 60 mg/kg, and cyclophosphamide 100 mg/kg. PBSC (≥7.5 × 108 nucleated cells/kg) were collected following priming with G-CSF and were either immediately cryopreserved (48 patients; cohorts A and B) or were first processed for CD34+ enrichment (40 patients; cohorts C and D). Patients in cohorts A and C received PBSC on day 0; patients in cohorts B and D received 25% of their nucleated cells on day −2 and 75% on day 0 (split reinfusion). Patients in cohorts A, B, and C were primed with G-CSF 10 μg/kg, subcutaneously (SC), once a day; patients in cohort D were primed with 5 μg/kg G-CSF, SC, twice daily (bid). Bid administration of G-CSF yielded 2.3 to 4.7 × higher numbers of CD34+ cells in the PBSC product than the same total dose given once a day (P = .002). Reinfusion of 25% of unselected PBSC on day −2 (median, 2.26 × 108/kg nucleated cells [range, 1.7 to 3.3 × 108/kg]) with the remaining cells reinfused on day 0 resulted in earlier granulocyte recovery to ≥500/μL when compared with reinfusion of all stem cells on day 0 (group B, median of 8 days [range, 7 to 11] v group A, 10 days [range, 8 to 11], P = .0003); no schedule-dependent difference was noted in reaching platelet independence (group B, 11.5 days [range, 5 to 21]; group A, 12 days [range, 8 to 24], P = not significant). Split schedule reinfusion of CD34+-selected PBSC did not accelerate granulocyte recovery. In groups D and C, the median number of days to granulocyte recovery was 12 (range, 8 to 22) and 11.5 (range, 9 to 13); patients became platelet independent by day 15 (range, 6 to 22) and 14 (range, 12 to 23), respectively. CD34+-selected PBSC rescue decreased the incidence of postreinfusion nausea, emesis, and oxygen desaturation in comparison to unselected PBSC reinfusion (P ≤ .005 for each). Hematopoietic recovery may be accelerated by earlier reinfusion of ≈ 2.26 × 108/kg unselected nucleated cells. Earlier recovery may be triggered by components other than the progenitors included in the CD34+ cell population. Sustained hematopoietic recovery can also be achieved with CD34+-selected PBSC alone. Dosing of G-CSF on a bid schedule generates higher CD34+ cell yield in the leukapheresis product. Whether even earlier “sacrificial” reinfusion of approximately 2 × 108/kg unselected nucleated cells concomitant with the administration of high-dose chemotherapy would reduce the duration of absolute granulocytopenia further while initiating sustained long-term hematopoietic recovery will require further investigation.