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

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.

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.

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).

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.