Plerixafor and G-CSF Versus Cyclophosphamide and G-CSF for Stem Cell Mobilization in Patients with Multiple Myeloma.

High dose melphalan and autologus stem cell transplant remains an effective treatment for patients with either early or refractory multiple myeloma (MM). Collection of sufficient numbers of stem cells for more than one transplant is optimal. G-CSF with chemotherapy, particularly cyclophosphamide (CY/G-CSF), has been a widely used and effective regimen for stem cell collection in MM. Plerixafor, a CXCR4 antagonist, when combined with G-CSF has been shown in a large randomized clinical trial to be superior to G-CSF alone. A comparison of plerixifor/G-CSF to CY/G-CSF is presented here.

We performed a single institution retrospective analysis of 365 patients with MM who underwent stem cell mobilization and harvest at the University of Pennsylvania Abramson Cancer Center from January 2002 to December 2007. All patients were harvested early in the course of their disease. 76 patients were excluded from this analysis (23 had incomplete data on induction regimen, 19 had incomplete data on stem cell collection, 16 had incomplete data on mobilization regimen, 10 underwent allogeneic transplants, 2 had bone marrow rather than peripheral blood harvests, 2 had stem cells collected at an outside institution, 2 had chemotherapy mobilization other than CY and 2 had medical complications prior to harvest and after mobilization). Therefore, 289 patients were included in the analysis; 16 received plerixafor/G-CSF, 198 received CY/G-CSF, and 75 received G-CSF alone.

The median number of collected stem cells was 7.95 × 10⁶ CD34+/kg in plerixafor/G-CSF group, 7.7 × 10⁶ CD34+/kg in Cy/G-CSF group and 4.5 × 10⁶ CD34+/kg in G-CSF alone group. The median number of apheresis days was 2 days, 2 days and 4 days respectively. The percentage of the patients who collected ≥ 6 × 10⁶ CD34+/kg in < 3 apheresis was 63% (10/16), 62% (123/198) and 19% (14/75) respectively. The percentage of the patients who collected ≥ 6 × 10⁶CD34+/kg <5 apheresis was 81% (13/16), 69% (136/198) and 23% (17/75) respectively. The mean CD34+/kg collected erither after CY/G-CSF or plerixafor/G-CSF was higher than G-CSF alone (p<0.0001 for each analysis).

This analysis suggests that plerixafor/G-CSF and CY/G-CSF mobilization result in similar and adequate stem cell harvest numbers for autologous stem cell transplantation for MM. Both approaches are superior to G-CSF alone. The choice of plerixafor/G-CSF vs CY/G-CSF for stem cell mobilization will therefore depend on further analysis of the relative costs, toxicities and long term outcome of these regimens.

Stadtmauer:genzyme: Consultancy.