Method of Autologous Stem Cell Mobilization Does Not Influence Transplant Outcome

No standard method for HSC mobilization prior to autologous stem cell transplant (ASCT) exists. We performed a retrospective analysis on consecutive adult patients (pts) undergoing mobilization for ASCT between 1/2009 and 1/2012 to compare efficacy of mobilization method and transplant outcome. Method of mobilization was per the discretion of the attending physician. Chemotherapy and G-CSF (Chemo/G) were used if therapy or cytoreduction was necessary for the underlying malignancy. Per institutional guideline cytokine only mobilization used G-CSF (G) 10 ug/kg daily with apheresis starting on day 5 and plerixafor (G/P) 0.24 mg/kg was added on day 4 if the peripheral blood CD34+ cells/ul was < 15. A total of 343 pts underwent 362 attempts at collection, 192 with G/P, 135 with G alone, and 35 after chemo/G. The median days of apheresis for all three groups was 2 (range 1-4) and the number of cumulative CD 34 cells collected after mobilization was 5.7(0-19), 6.8 (1.9-20.9), and 6.3(0-19) million/kg in the G/P, G, and chemo/G groups, respectively (p=NS). Failure to mobilize CD34 cells was defined as never reaching 10 or greater peripheral blood CD34+ cells/ul or collecting less than 2 million CD34+ cells/kg. Per institutional guideline 192 of 327 collections (59%) starting with G-CSF alone required the addition of plerixafor. Nine of 192 collections (4.6%) in the G/P group failed to mobilize and 2 were rescued with a second G/P mobilization. Twelve of 35 collections (34%) in the chemo/G group failed to mobilize and 8 were subsequently mobilized adequately with G/P.  Overall, 11/343 (3.2%) pts failed to mobilize adequate CD34+cells. Engraftment and day 100 transplant outcomes were not different between the groups. In conclusion, the method of mobilizing HSC for ASCT does not seem to affect clinical outcome, pts that fail mobilization after chemo/G for treatment of active disease or cytoreduction can be remobilized with G/P, and our current institutional protocol to begin mobilization with G alone and add plerixafor on day 4 as described above allows a high rate of mobilization success.  Further prospective studies are needed to assess pharmacoeconomic and quality of life issues related to HSC mobilization.