Peripheral Blood Stem Cell (PBSC) Mobilization in Patients with Multiple Myeloma: Low Dose Versus Intermediate Dose Cyclophosphamide.

Aim: Autologous peripheral blood stem cell transplant (PBSCT) is standard of care for multiple myeloma patients younger than 65 years of age. However there is no agreement on mobilization regimen for PBSC collection. We have compared efficacy and toxicity of low dose & intermediate dose of cyclophosphamide for stem cell mobilization. Methods: Eighty-seven patients with multiple myeloma had stem cell mobilization: Intermediate dose cyclophosphamide (3 to 4 gm/m2) [ID-CY] was used between Jan 1995 to Jun 2002 and low dose cyclophosphamide (1 to 2 gm/m2)[LD-CY] was used between 2002 and 2004. Mobilization chemotherapy: LD-CY or ID-CY was infused along with hydration, antiemetics and mesna. Stem cell collection was planned between day 10 to day 14 after chemotherapy and G-CSF 10 ug/kg (5 to 20 ug/kg) was started 4 days prior to stem cell collection. PBSC collected by processing 7 litres of blood by Fenwal CS3000 (Baxter) or Cobe Spectra. Statistical Analysis: The Mann-Whitney U and Kruskal-Waliis test were used for comparison between treatment groups. Chi-Square and Fisher exact test were used for comparisons of categorical variables Result: There were 87 patients of multiple myeloma, 61 in LD-CY group and 26 in ID-CY group. There was no statistically significant difference between two groups for basic demographic, disease parameters & prior duration of treatment. The median G-CSF/kg dose was similar in both groups. Comparison of Stem cell collection and toxicity: LD-CY Vs ID-CY CD34 Yield LD-CY ID-CY P Number of Patients 61 26 Total CD34/kg Median (Range) 5.17 (0.23 to 17.3) 7.71 (0.08 to 26.4) 0.018 Total CD34/kg/L Median (Range) 0.62 (0 to 2.47) 1.07 (0.01 to 3.77) 0.010 CD34/kg on 1st day of leukapheresis 2.33 (0.03 to 15.8) 5.11 (0.04 to 15.9) 0.001 number of patients collected > 2 x 10^6/kg 54/61 (88%) 24/26(92%) Number of Leukapheresis Median (Range) 2 (1 to 5) 2 (1 to 3) 0.001 Number of patients had febrile neutropenia 8/61(13%) 10/26 (38%) 0.0085 Number of patients required antibiotics 8/61 (13%) 10/26(38%) 0.0085 Number of patients requiring hospitalisation 10/61(16.39%) 11/26 (42.30%) 0.010 Conclusion: There was statistically significant higher stem cell yield with ID-CY as compared to LD-CY, however at the cost of increased toxicity. In LD-CY group 88% patients had >2 x106/kg stem cells collected which is sufficient for single autograft. We conclude that LD-CY mobilisation chemotherapy is adequate for patients who are planned for single autograft with minimal toxicity.