Optimal methods of stem cell mobilization in multiple myeloma are undefined, and contaminating clonotypic cells could contribute to disease recurrence. A phase 2 trial of intravenous melphalan (60 mg/m2) and granulocyte colony-stimulating factor (G-CSF) (10 μg/kg/d) for mobilization was performed. To enhance reliability, contamination was assessed with 2 sensitive methods, immunoglobulin light and heavy chain variable region patient-specific limiting-dilution polymerase chain reaction (PCR). We evaluated 29 stem cell components (SCCs) from 15 patients; for 9 SCCs, only VL PCR was used because of light chain disease or technical problems with VH primers. For 20 SCCs, VL and VH PCR results were highly correlated (r2 = 0.93, P < .01), with 35% (7 of 20) having identical estimates. VH PCR gave significantly higher estimates for 8 - and VL PCR for 5 - SCCs, supporting the utility of using 2 methods. Estimated clonotypic contamination per SCC was 0.0009% (range, 0%-0.1%) or 0.5 × 104 clonotypic cells per kilogram (range, 0-41.2 x 104/kg), and contamination correlated with CD34+ cells collected (r2 = 0.42, P < .01). Melphalan-mobilized SCCs contain minimal clonotypic contamination.
ASJC Scopus subject areas
- Cell Biology