Predictors of Unsuccessful Mobilization with Granulocyte-Colony Stimulating Factor (G-CSF) Alone In Patients with Hematological Malignancies Undergoing Autologous Hematopoietic Stem Cell (AHSCT) Transplant
Authors: Chow Signy , Ormond D. George , Lazo-Langner Alejandro , Howson-Jan Kang , Xenocostas Anargyros 
Published: October 2019

Abstract
Abstract 4445

Background
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.

Patients and Methods
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.

Results
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.

Conclusions
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.

Disclosures:
Howson-Jan: Merck: Research Funding.