MULTIPLE-MYELOMA - REDUCED PLASMA-CELL CONTAMINATION IN PERIPHERAL-BLOOD PROGENITOR-CELL COLLECTIONS PERFORMED AFTER REPEATED HIGH-DOSE CHEMOTHERAPY COURSES

The possibility of reducing tumour cell contamination by cytotoxic dru g courses prior to peripheral blood progenitor cell (PBPC) collection was evaluated in two consecutives groups of multiple myeloma (MM) pati ent candidates for autograft, All patients were at disease onset and r eceived two VAD (vincristine, doxorubicin and dexamethasone) courses a s initial debulking, In the rst group (44 patients), mobilization and harvest were performed 'upfront', after a single cyclophosphamide (CY) administration of 4 g/m(2); in the second group (17 patients), PBPC w ere collected at the end of a high-dose sequential chemotherapy progra mme, including: CY 5 g/m(2), etoposide (VP16) 2 g/m(2), a chemotherapy free interval with three courses of high-dose dexamethasone, a final mobilizing CY at 7 g/m(2), G-CSF was given following each high-dose cy totoxic drug, Cytofluorimetric analysis was performed to quantify prog enitors (CD34(+) cells) and plasma cells, identified by the high CD38 expression and/or CD38 and CD138 coexpression. Large amounts of PBPC w ere collected in either group (median harvested CD34(+)/kg: 15.8 x 10( 6) and 13.4 x 10(6), respectively; P=0.9). Circulating plasma cells we re significantly higher in patients mobilized 'upfront' compared to th ose who received the high-dose sequence (median peak values of CD38(br ight)/mu l: 39 and 10, respectively; P=0.02); a similar difference was observed in the amount of contaminating plasma cells in the harvest p roducts (median CD38(bright)/kg: 7.4x10(6) and 1.3 x 10(6), respective ly; P=0.02), The results demonstrate that an in vivo purging approach is feasible in myeloma patients through repeated high-dose chemotherap y courses; this may provide less-contaminated material suitable for fu rther in vitro purging procedures.