Preceding chemotherapy, tumour load and age influence engraftment in multiple myeloma patients mobilized with granulocyte colony-stimulating factor alone

Haematopoietic growth factors, especially granulocyte colony-stimulating fa ctor (G-CSF), are frequently utilized alone for peripheral blood stem cell (PBSC) procurement to avoid the morbidity associated with high-dose chemoth erapy (HDT). Moreover, the cytotoxic agents used may not be the most optima l therapy for the malignancy. It also makes scheduling of apheresis easier. Factors having an impact on PBSC procurement and engraftment after HDT wer e analysed in 117 multiple myeloma patients mobilized with G-CSF (10-16 mug /kg, median 12 mug/kg) alone using Cox regression analysis. A median of 6.2 x 10(6) CD34 cells/kg (range 0.6-34.1) were procured during leukapheresis and a median of 2.5 x 10(6) CD34 cells was infused after the first HDT (ran ge 0.3-23.9). The only factor significantly affecting optimal PBSC procurem ent was duration of preceding conventional chemotherapy (P = 0.002). Granul ocyte recovery was prompt in almost all patients, 75% of whom attained a gr anulocyte count of 0.5 x 10(9)/l by day 13 (median 11, range 7-19). However , platelet recovery to both 20 x 10(9)/l (median 12 d, range 8-50+) and 50 x 10(9)/l (median 20 d, range 7-205+) varied widely. On univariate analysis , factors influencing platelet recovery were the number of CD34 cells/kg in fused, age, beta (2)-microglobulin levels, response to preceding therapy, b one marrow plasmacytosis and duration of prior therapy. Factors attaining s ignificance on multivariate analysis included number of CD34 cells/kg infus ed (P = 0.007), beta (2)-microglobulin levels (P = 0.0001), most probably r epresenting disease load, and age (P = 0.002). Patients with high tumour bu rden, i.e. beta (2)-microglobulin levels > 2.5 mg/l, probably benefit from chemotherapy for mobilization both in terms of cytoreduction and adequate s tem cell mobilization resulting in accelerated engraftment.