Impact of Stem Cell Mobilization with Chemotherapy Versus G-CSF Alone for Multiple Myeloma Patients with Suboptimal Response Before Autologous Stem Cell Transplant.

BACKGROUND

Autologous stem cell transplantation (ASCT) remains the standard consolidation therapy for multiple myeloma (MM). Peripheral blood stem cell mobilization, performed using G-CSF alone or in combination with chemotherapy (chemo-mobilization), is a crucial step in this process. Although chemo-mobilization enhances CD34⁺ yields, its effect on disease control and post-transplant outcomes in the era of novel agents remains unclear.

PATIENTS AND

METHODS

We retrospectively analyzed 67 MM patients who underwent ASCT at our institution. Thirty-two patients (47.8%) received chemo-mobilization with cyclophosphamide (37.5%) or KD-PACE plus G-CSF (62.5%) and 35 (52.2%) received G-CSF alone. The primary endpoint was overall response rate (ORR) at day 90 post-transplant, while transplant outcomes were analyzed as secondary endpoints. Propensity score-adjusted Cox models were used to assess prognostic factors.

RESULTS

Chemo-mobilization yielded a higher median CD34⁺ collection (7.9 × 10⁶/kg vs. 6.6 × 10⁶/kg; P = .035), fewer apheresis sessions (P = .005), and reduced plerixafor use (P = .005) compared with G-CSF alone. Among chemo-mobilized patients, 89% showed decreased tumor burden and 21% achieved improved response pre-ASCT. ORR at day 90 post-ASCT was comparable between groups (90.6% vs. 94.3%; P = .569). Complete remission (CR+sCR) and MRD negativity were higher in the G-CSF cohort (65.7% vs. 43.8%, P = .008; 90% vs. 60%, P = .007). At 20-month median follow-up, 3-year PFS was 48.4% versus 89.6% (P = .031); OS did not differ significantly (P = .230). Achieving ≥ VGPR pre-ASCT predicted improved PFS (HR 4.04, 95% CI, 1.04-15.71; P = .044).

CONCLUSION

Chemo-mobilization improves stem cell yield and reduces tumor burden without added toxicity. Achieving ≥ VGPR before ASCT was associated with lower relapse risk and superior PFS.