Effective CD34+ Stem Cell Mobilization with Low-Dose Pegfilgrastim.

Introduction: Numerous strategies utilizing chemotherapy followed by filgrastim allow for the successful mobilization of peripheral hematopoietic progenitor cells. To eliminate the need for self-administration of multiple growth factor injections and to minimize cost, we piloted a mobilization strategy consisting of low-dose Pegfilgrastim and chemotherapy.

Methods: Seven consecutive patients scheduled to undergo hematopoietic progenitor cell transplant for hematologic malignancy received a single 6mg injection of Pegfilgrastim 24–48 hours after chemotherapy. The targeted CD34+ collection was 5x10⁶cells/ kg. The number of apheresis, CD34+ cell yield, time to engraftment and toxicities were recorded. These patients were compared to the 15 previous patients who received Filgrastim and chemotherapy for mobilization.

Results: In the pilot population, the median age was 60 (range: 39–67) years. Chemotherapy priming before Pegfilgrastin for three patients with multiple myeloma and two with stage IV mantle cell lymphoma was 4.5grams/m² of cyclophosphamide; one patient with relapsed, stage IV Hodgkin’s disease received ICE and one multiple myeloma patient with a serum creatinine of 3.1mg/dL, received 2.5grams/m² of cyclophosphamide. Five patients required a single apheresis, two patients required two apheresis collections. The median CD34+ yield was 6.7 x10⁶/kg (range: 3.2–13.7). The median time to neutrophil engraftment was 10 days (range: 9–12). The median time from Pegfilgrastim to apheresis was 9 days (range: 7–10). The Pegfilgrastim cost per patient was $3,250.00. Toxicity was limited to grade II bone pain.

The comparison group consisted of seven multiple myeloma, four leukemia and four lymphoma patients. Their median age was 51.5 years (range: 24–67). The median number of apheresis procedures was 2 (range: 1–3). The median CD34+ yield was 5.6 x10⁶/kg (range: 2.9–17.6). The median time to neutrophil engraftment was 11 days (range: 9–11). The median time from cytokine to apheresis was 8.5 days (range: 3–16). The median cost of Filgrastim per patient was $3,650.00 (range: $2,290–$8,760). The median number of Filgrastim injections was 10 (range: 10–14). Toxicity was limited to grade II bone pain.

Discussion: In a two cohorts of patients with hematologic malignancies Pegfilgrastim as compared to Filgrastim resulted in a decreased cytokine cost, a fewer number of apheresis collection procedures, a more predictable time to first apheresis and no self-administration of medication. There was no significant difference in the time to engraftment.

Conclusion: Low-dose Pegfilgrastim in conjunction with chemotherapy results in as effective CD34+ progenitor cell mobilization with less drug cost and apheresis time as compared to Filgrastim with chemotherapy.