(PA-384) Impact of CD34+ Cell Infusion Dose on Immune Reconstitution and Survival in Multiple Myeloma After Autologous Stem Cell Transplantation

Autologous stem cell transplantation (ASCT) remains a cornerstone therapy for multiple myeloma (MM). However, the optimal CD34⁺ cell infusion dose and its relationship with immune reconstitution and survival are unclear. Oligoclonal bands (OB), indicating B-cell recovery, may serve as markers of effective immune reconstitution. This study aimed to evaluate the prognostic impact of CD34⁺ cell infusion dose and to explore its association with OB formation, in order to inform transplant optimization.

Methods:   

A total of 176 MM patients who underwent early ASCT were retrospectively analyzed and stratified by CD34⁺ cell dose (< 5×10⁶/kg vs. ≥5×10⁶/kg). Clinical characteristics, treatment responses, survival outcomes, and OB formation were compared. Prognostic factors were identified via Cox regression, and a nomogram was constructed to predict overall survival (OS).

Results:   

Patients receiving a CD34⁺ cell infusion ≥5×10⁶/kg demonstrated significantly improved progression-free survival (PFS: 50 vs. 40 months, p=0.020) and OS (not reached vs. 76 months, p< 0.001) compared to those receiving < 5×10⁶/kg. This high-dose group also showed deeper remission (p=0.034), lower early relapse rates (9.1% vs. 24.2%, p=0.006), and more durable minimal residual disease (MRD) negativity (≥2 years: 70.5% vs. 51.5%, p=0.003). Immune reconstitution analysis revealed significant increases in total T cells, CD8⁺ T cells, and B cells post-ASCT (p< 0.001), alongside a modest reduction in CD4⁺ T cells (p=0.002) and no significant change in NK cells (p=0.248). OB was detected in 38.6% of patients and was significantly associated with high CD34⁺ dose (44.5% vs. 28.8%, p=0.038). OB-formation patients exhibited longer PFS (66 vs. 37 months, p< 0.001) and OS (not reached vs. 91 months, p=0.009). Combined analysis revealed that CD34⁺ ≥5×10⁶/kg with OB formation conferred the greatest OS benefit (p< 0.001), though no marked PFS benefit. CD34⁺ ≥5×10⁶/kg, MRD negativity, and OB formation were independent protective factors. A nomogram incorporating these variables demonstrated strong predictive accuracy (C-index: 0.768; AUC: 0.864, 0.880, 0.749 for 1-, 3-, 5-year OS) , supporting its clinical utility.

Conclusions:   

This study identifies CD34⁺ ≥5×10⁶/kg infusion as a potential optimal threshold that enhances immune reconstitution and promotes OB formation, thereby improving deep remission and long-term survival after ASCT.