Intermediate-dose CY and G-CSF more efficiently mobilize adequate numbers of PBSC for tandem autologous PBSC transplantation compared with low-dose CY in patients with multiple myeloma

Background: Autologous PBSC transplantation is the standard care for patients with multiple myeloma. The most common regimen used to mobilize PBSC consists of CY and G-CSF. Methods: We retrospectively analyzed the efficacy and toxicity of two regimens of CY for PBSC mobilization: low-dose CY (1-2 g/m², LD-CY, n = 61) plus G-CSF, and intermediate-dose CY (3-4 g/m², ID-CY, n = 26) plus G-CSF. Results: In the LD-CY group, 5.17 (0.23-17.3) × 106 CD34⁺ cells/kg, and in the ID-CY group 7.71 (0.08-26.4) × 10⁶ CD34⁺ cells/kg (P = 0.018), were collected. Although ≥2 × 10⁶/kg CD34⁺ cells were collected in 89% of the LD-CY group and 92% of the ID-CY group, this was achieved after a single leukapheresis in 54% of the LD-CY group and 92% of the ID-CY group (P = 0.0001). Patients who are to have tandem autologous PBSC transplants require ≥ × 10⁶/kg CD34⁺ cells. This was achieved in only 65% patients in the LD-CY group but 88% in the ID-CY group (P = 0.05). Among patients who had not had prior melphalan and/or >12 months of prior treatment, 74% in the LD-CY group and 100% in ID-CY group mobilized ≥4 × 10⁶/kg CD34⁺ cells. Febrile neutropenia was more frequent in the ID-CY group (38% vs. 13%). Discussion: In conclusion, compared with LD-CY, patients receiving ID-CY were more likely to collect a total CD34+ cell number adequate for tandem autologous PBSC transplantation. The increased toxicity was manageable and considered acceptable.