Stem cell factor and high-dose twice daily filgrastim is an effective strategy for peripheral blood stem cell mobilization in patients with indolent lymphoproliferative disorders previously treated with fludarabine: results of a Phase II study with an historical comparator

Fludarabine exposure leads to impaired peripheral blood stem cell (PBSC) mobilization in indolent lymphoproliferative disorders (LPD). We previously reported that only 34% of fludarabine-exposed patients mobilized successfully using granulocyte-colony stimulating factor (G-CSF; median 10 μg/kg/day) with or without chemotherapy, with unpredictable kinetics and moderate infectious morbidity. Stem cell factor (SCF) plus high-dose twice daily (b.d.) G-CSF may improve mobilization in these patients. SCF 20 μg/kg/day subcutaneously was given from day 1, G-CSF 12 μg/kg b.d. subcutaneously from day 4, apheresis commenced from day 6. Previous study patients served as historical controls. Thirty five patients with indolent LPD were enrolled, median age was 54 years (range 31–66), 66% male, median cumulative prior fludarabine dose was 660 (405–900) mg. Overall, 22 patients (63%) collected ⩾2.0 × 10 6 /kg PBSC (success), compared to 34% controls (odds ratio (OR) 3.2; 95% confidence interval (CI) (1.2, 9.3); P =0.021). Median CD34 + yield overall was 2.3 × 10 6 /kg (0.53–8.97) from median four (2–6) aphereses. Study patients ⩾50 years mobilized successfully more frequently than controls (58 versus 17%; P =0.0065). Adjusting for age, successful mobilization remained significantly higher in the current study (OR 4.2; 95% CI (1.4, 14.0); P =0.008). SCF/high-dose b.d. G-CSF improves PBSC mobilization efficacy after fludarabine exposure, over mobilization using G-CSF as the mobilizing cytokine. This combined growth factor strategy is a preferred mobilization method for fludarabine-exposed patients.