Comparison of peripheral blood progenitor cell mobilization in patients with multiple myeloma: high-dose cyclophosphamide plus GM-CSF vs G-CSF alone.

The best method for peripheral blood progenitor cell (PBPC) mobilization in patients with multiple myeloma (MM) remains controversial. We report the results of two different methods of PBPC collection for autologous transplantation in 40 patients with stage II or III MM. In group I (n = 18), HD-CY, 4 g/m2 i.v., was administered followed by GM-CSF, 8 microg/kg/day s.c., until the end of collection, starting the leukaphereses after hematological recovery (>1 x 10(9)/l WBC). In group II (n = 22), G-CSF, 10 microg/kg/day s.c., was used alone until the last day of collection, starting consecutive aphereses on the 5th day. A minimum of two aphereses were performed to collect at least 2 x 10(6)/kg CD34+ cells. Both patient groups were comparable for age, sex and clinical prognostic features as well as previous therapies. In group I, the median yields per pheresis were: MNC 1.47 (1.38-2.32) x 10(8)/kg, CFU-GM 0.82 (0.18-13.2) x 10(4)/kg and CD34+ cells 1.98 (0.96-6.96) x 10(6)/kg. In group II these results were: MNC 2.44 (2.06-3.6 x 10(8)/kg) (P = 0.03), CFU-GM 0.75 (0.16-7.8) x 10(4)/kg and CD34+ 1.05 (0.32-3.4) x 10(6)/kg (P = 0.02). The median number of aphereses performed in each group was 5 (4-12) with a median of 5.24 +/- 2.51 in group I and 3 (2-6) with a median of 3.1 (+/- 0.91) in group II (P = NS). Hospitalization for PBPC mobilization was required in all patients in group I and the treatment-related toxicity was greater in this group: 12 patients (66%) developed fever requiring antibiotics during the neutropenic period after HD-CY and six (33%) patients required transfusion support. After receiving busulfan 12 mg/kg p.o. and melphalan 140 mg/m2 i.v., as the conditioning regimen, the median periods to reach granulocytes (>0.5 x 10(9)/l) and platelet (>20 x 10(9)/l) engraftment were 12 and 11 days respectively (ranges 8-20 and 10-16) in group I (HD-CY plus GM-CSF group), and 11 and 13 days respectively (ranges 7-42 and 10-38) in group II (G-CSF group) (P = NS). In conclusion, these data suggest that although HD-CY plus GM-CSF is superior to G-CSF alone based on mean CD34+ cell yield per pheresis, adequate CD34+ cell collections can be achieved with G-CSF alone in most MM patients with less toxicity and with simplification of the procedure.