Comparing stem cell mobilization with chemotherapy and cytokine (G-CSF) versus cytokine alone in myeloma patients (MOCCCA): a randomized phase II, open-label, non-inferiority trial.

In fit patients with newly diagnosed myeloma, high-dose chemotherapy (HDCT) followed by autologous stem cell transplantation (ASCT) is considered standard of care. For mobilization of CD34+ cells for ASCT, combined cytotoxic chemotherapy and G-CSF is commonly used. However, the importance of cytostatic chemotherapy for reliable mobilization remains unclear. This prospective randomized phase II non-inferiority trial compared G-GSF only (G) compared to standard chemotherapy/G-CSF (CG) for CD34+ mobilization. The primary endpoint was a less than 15% difference in successful stem cell collection ( ≥ 5.0 × 10⁶ CD34+ cells/kg b.w. in a single day collection procedure without additional stimulation with plerixafor) with the G regimen. 136 patients were 1:1 randomized. With an 18% difference in favor of the CG therapy, the non-inferiority margin was not maintained (95% CI 1%, 34%, p = 0.04). The median total CD34+ yield was 9.99 × 10⁶/kg b.w. in CG patients and 7.42 × 10⁶/kg b.w. in patients with G-CSF alone (p < 0.001). Ultimately, 130 (96%) patients proceeded to HDCT with ASCT. There were no differences in adverse events, hematologic engraftment, quality of life, or pain perception between the groups. Our data indicate that G-CSF only is inferior to chemotherapy with G-CSF for peripheral CD34+ stem cell mobilization. Trial registration SNCTP #: SNCTP000002952; Trials.gov #: NCT03442673.