Influence of Prior Lenalidomide Exposure On Peripheral Blood Progenitor Cell Mobilization for Autologous Stem Cell Transplant in 144 Consecutive Patients with Multiple Myeloma.

Abstract 3223

Poster Board III-160

There are concerns that prolonged exposure to lenalidomide (len) impairs the peripheral blood progenitor cell (PBPC) yield in patients (pts) undergoing autologous peripheral blood stem cell transplant (ASCT) for multiple myeloma. To evaluate the effect of len on PBPC yield, we retrospectively analyzed 144 consecutive pts undergoing PBPC harvest prior to ASCT for multiple myeloma between July 1, 2007 and June 30, 2009. Exclusion criteria included prior ASCT or prior treatment with an alkylating agent. Of the evaluable patients, 67 pts received at least one cycle of len as part of their pre-harvest therapy (median # of cycles 4 (range 1-28)) and 63 received non-len containing regimens. Median age for all pts was 57 years and was similar between the two groups.

Initial PBPC harvest was unsuccessful (defined as collection of <2.5 × 10⁶ CD34+ cells/kg) in 6 of 52 (11.5%) G-CSF mobilized pts who had prior len exposure, compared to 4 of 49 (8.2%) non-len exposed pts mobilized with G-CSF (p = NS). One pt in each group underwent ASCT after collection of <2.5 × 10⁶ CD34+ cells/kg and both engrafted normally. One other cyclophosphamide/G-CSF mobilized and len exposed pt failed initial harvest as well. Of the 11 total pts in whom initial PBPC harvest failed, a second attempt was successful in 10 (3 G-CSF/GM-CSF; 6 plerixafor/G-CSF; 1 cyclophosphamide/G-CSF) and not attempted in 1.

The median number of PBPCs harvested in len exposed pts mobilized with G-CSF alone was 6.36 × 10⁶ CD34+ cells/kg (range 2.1-20.62), compared to 8.22 × 10⁶ CD34+ cells/kg (range 2.29-46.1) in non-len exposed pts mobilized with G-CSF alone (p=0.001 by Mann-Whitney test). Len treated pts required more apheresis sessions for adequate PBPC harvest (1.89 days vs 1.57 days (p<0.05)) than non-len treated pts when G-CSF was used alone as the mobilizing agent. Eleven (24%) of the len treated pts and 6 (13%) of the non-len treated pts were not able to collect ≥ 5.0 × 10⁶ CD34+ cells/kg with G-CSF alone (p=0.42). Among 10 G-CSF mobilized pts who received >6 cycles (median # of cycles 11, range 7-28) of len prior to PBPC harvest, the median PBPC yield was 6.44 × 10⁶ CD34+ cells/kg collected over a median of 2 days. Seven of the 10 collected enough PBPCs for two transplants. One pt receiving 7 cycles of len failed initial PBPC harvest with G-CSF alone and subsequently successfully harvested with plerixafor/G-CSF.

Nineteen pts were initially mobilized for PBPC harvest with cyclophosphamide/G-CSF. Nine had prior len exposure (median # of cycles 4 (range 3-8)) and the PBPC yield for each pt was well above that required for tandem ASCT. There was no difference in the number of days to harvest between the len treated and non-len treated pts and most harvested in 1 apheresis attempt. One patient with 4 cycles of prior len therapy did not collect an adequate number of PBPCs but subsequently successfully harvested enough PBPCs for 2 ASCTs with plerixafor/G-CSF.

In summary, most pts treated with len containing regimens prior to PBPC harvest were able to collect adequate numbers of PBPCs for tandem ASCT with G-CSF mobilization. All len treated pts in our series who failed G-CSF mobilization and underwent a second attempt at PBPC harvest using plerixafor/G-CSF or cyclophosphamide/G-CSF as the mobilizing agent were able to successfully harvest adequate numbers of PBPCs for ASCT. In this retrospective review, the difference in PBPC yield between len treated and non-len treated pts did not impact the ability to proceed to ASCT.