Predictors of Unsuccessful Mobilization with Granulocyte-Colony Stimulating Factor (G-CSF) Alone In Patients with Hematological Malignancies Undergoing Autologous Hematopoietic Stem Cell (AHSCT) Transplant

Mobilization of hematopoetic stem cells (HSC) in patients undergoing AHSCT for hematological malignancies is usually done using hematopoietic growth factors such as G-CSF with or without concurrent use of chemotherapy or other agents such as plerixafor. While studies comparing G-CSF alone to combination regimens demonstrate an increase in the yield of stem cells in the latter case, mobilization with G-CSF alone is still effective and represents the standard of care at our institution. Therefore, we aimed to identify potential predictors of mobilization failure with G-CSF alone in patients undergoing AHSCT for hematological malignancies and for which alternative regimens might be considered.

We conducted a single centre retrospective case-control study of all consecutive patients who underwent at least one mobilization attempt with G-CSF for an AHSCT at the London Health Sciences Centre in London, Ontario, Canada between January 2000 and December 2008. The mobilization regimen consisted of G-CSF 10 μ g/kg/day for 4 days with collection on days 5 and 6. The primary outcome was successful mobilization defined as the collection of at least 2.0×10⁹ CD34⁺cells/kg. The secondary outcome was the mean yield of stem cells mobilized. Groups (successful vs. unsuccessful mobilization) were compared using unpaired Student's t, Mann-Whitney U, χ2 or Fisher's exact tests, as appropriate. Logistic regression analysis was conducted using an unsuccessful mobilization as the dependent variable. CD34⁺cells/kg yields were compared using unpaired Student's t tests or one-way ANOVA.

During the study period, mobilization was attempted in 293 patients (134 MM, 57 HD, 86 NHL, 17 Other). The mean age was 47.5±12.3 years. 251 patients (86.6%; 95%CI 82.3, 90.1) were successfully mobilized and 244 (83.6; 95%CI 78.9, 87.4) underwent AHSCT. The median yield was 3.55 ×10⁶CD34+ cells/kg (Interquartile range 2.50–5.30). On univariate analysis, mobilization success was influenced by the number of previous chemotherapy regimens and underlying diagnosis (P<0.001 each), but not by age (P=0.114), sex (P=0.860) or prior radiotherapy (P=0.454). A diagnosis of NHL and number of previous chemotherapy regimens were predictors of unsuccessful mobilization on multivariate analysis (Table 1). CD34⁺cells/kg yield was influenced by diagnosis and previous chemotherapy (P <0.001 each). The percentage of patients with successful and unsuccessful mobilization using G-CSF alone according to diagnosis and number of attempts is shown in Table 2.

HSC mobilization with G-CSF alone yields adequate collections for most patients. Patients with NHL and patients treated with 2 or more previous chemotherapy regimens that fail an initial mobilization attempt have higher failure rates and can be considered for alternate mobilization regimes.

Howson-Jan:Merck: Research Funding.