Correlation Between Pre-Collection CD34 Blood Concentrations and CD34 Collection Yield in Difficult-to-Mobilize Patients Given Plerixafor. –a Retrospective Single Center Study

Background Pre-collection CD34 blood concentrations have been shown to predict collection yield in patients mobilized with G-CSF +/- chemotherapy. We aimed to study this association in a cohort of difficult to mobilize patients who were given Plerixafor in addition to standard mobilization regimen.

Methods We performed a retrospective cohort study of all cases (n=58) of patients (n=31) who were difficult to mobilize and given Plerixafor prior to collection between the years 2009 and 2014. Correlation between pre-collection CD34 and collection yield was measured using the Pearson's chi squared test and goodness of fit with a linear regression. Two-sided p values are presented.

Results Patients' median age was 45 (range, 5–71) years, 54% were female. Baseline disease was lymphoma (74%), Multiple Myeloma (10%) and solid malignancies (16%). Thirty two percent of patients had >2 previous therapies, 36% prior radiation therapy and 42% chemorefractory disease. Seventy six percent of cases were collected at steady state (G-CSF + Plerixafor) and 24% collected post chemotherapy and G-CSF.

There was a significant correlation between pre-collection CD34 blood concentrations and CD34 collection yield (r=.93 (95% CI.88-.96, p<.001) with r² in logistic regression of .86, p<.001.  Receiver operating curve to predict sufficient CD34 collection (Figure) showed at a pre-collection CD34 blood concentrations of >9.5 cells/ul sensitivity was 88% (95% CI68.8-97.4) and specificity was 67.7% (95% CI48.6-83.3). For CD34 blood concentrations >19 cells/ul sensitivity was 84% (95% CI63.9-95.5) and specificity was 100% (95% CI 88.8-100.0). For CD34 blood concentrations of >9.5 cells/ul and >19 cells/ul the negative predictive and positive predictive values were 69%, 92% and 100%, 88%, respectively. 

Conclusion Pre-collection CD34 blood concentration in difficult to mobilize patients given Plerixafor is a strong predictor of successful collection with the value of >19 cells/ul associated with 84% sensitivity and 100% specificity.