DETECTION OF MALIGNANT B-CELLS IN PERIPHERAL-BLOOD STEM-CELL COLLECTIONS AFTER CHEMOTHERAPY IN PATIENTS WITH MULTIPLE-MYELOMA

Autologous transplantation after high-dose chemo or radiotherapy is now frequently used for the treatment of patients,vith multiple myeloma (MM), The collection of peripheral blood stem cells (PBSC) has a theoretical advantage over autologous bone marrow collection as the malignant plasmacytic contamination is believed to be lower, However, the extent of B cell contamination in PBSC has not been extensively investigated, Using an inmunoglobulin heavy chain gene 'fingerprinting' technique at diagnosis and during apheresis after one cycle of chemotherapy we detected a monoclonal population in 44% of PBSC samples (9 positives in 22 studied). There was no correlation between contamination and sex, age, Durie and Salmon classification, C-reactive protein and albumin, A significant correlation was observed with beta 2 microglobulin serum level (P = 0.02). Twenty one patients were grafted and up to the present, with a mean follow-up of 12 months, 6 patients have relapsed including 4 patients with contaminating B cells, Our results suggest that PBSC contamination, defines a 'poor risk' group Of patients, with poor prognosis, However, we could not exclude reinitiation of the disease by plasmacyte stem cells after grafting.