Abstract

Background: Autologous stem cell transplantation (auto-SCT) is a widely used treatment option in multiple myeloma (MM) patients. The optimal graft cellular composition is not known.

Study design and methods: Autograft cellular composition was analyzed after freezing by flow cytometry in 127 MM patients participating in a prospective multicenter study. The impact of graft cellular composition on hematologic recovery and outcome after auto-SCT was evaluated.

Results: A higher graft CD34⁺ cell content predicted faster platelet recovery after auto-SCT in both the short and long term. In patients with standard-risk cytogenetics, a higher graft CD34⁺ count (<2.5 × 10⁶/kg) was linked with shorter progression-free survival (PFS; 28 vs. 46 months, p = 0.04), but there was no difference in overall survival (OS) (p = 0.53). In a multivariate model, a higher graft CD34⁺CD133⁺CD38⁻ (>0.065 × 10⁶/kg, p = 0.009) and NK cell count (%gt;2.5 × 10⁶/kg, p = 0.026), lenalidomide maintenance and standard-risk cytogenetics predicted better PFS. In contrast, a higher CD34+ count (>2.5 × 10⁶/kg, p = 0.015) predicted worse PFS. A very low CD3⁺ cell count (≤20 × 10⁶/kg, p = 0.001) in the infused graft and high-risk cytogenetics remained predictive of worse OS.

Conclusions: Autograft cellular composition may impact outcome in MM patients after auto-SCT. More studies are needed to define optimal graft composition.