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 central in multiple myeloma, yet the optimal CD34+ infusion dose is uncertain. We retrospectively analyzed 176 newly diagnosed patients undergoing ASCT. Survival was estimated by Kaplan-Meier, and predictors were assessed by Cox regression. Among ASCT patients, a high CD34+ dose (≥5 × 106/kg) was associated with superior progression-free survival (PFS, p = 0.020), OS (p < 0.001), deeper responses (p = 0.034), and sustained minimal residual disease (MRD) negativity (p = 0.001). High dose correlated with oligoclonal bands formation (OB, p = 0.038), indicating immune reconstitution. Patients exhibiting both high CD34+ dose and OB constituted the best OS (p < 0.001). In multivariate analysis, CD34+ ≥5 × 106/kg independently predicted superior PFS (p = 0.014) and OS (p < 0.001). In sum, CD34+ ≥5 × 106/kg is a practical dosing target that couples immune reconstitution via OB formation to durable post-ASCT survival, with no incremental benefit above 10.64 × 106/kg.