Peripheral Blood CD34+ Percentage at Hematological Recovery after Chemotherapy Is a Good Early Predictor of Harvest: A Single-Center Experience

Several algorithms for early prediction of poor-mobilizing patients after chemotherapy and granulocyte colony-stimulating factor administration have been proposed. They generally define peripheral blood cut-off levels of CD34+ cells at a fixed day after starting chemotherapy, mostly with cyclophosphamide. To define an algorithm for early addition of plerixafor regardless of the chemotherapy regimen used, we retrospectively analyzed 280 chemomobilization attempts in 236 patients treated at our institution between 2002 and 2012. In multivariate analysis, CD34+ absolute count and CD34+ percentage upon total leukocyte count at day 1 (defined as the first day in which leukocytes reached a value > 1 × 109/L) were the only factors able to predict a total harvest ≥ 2 × 106 CD34+/kg. In patients with day 1 CD34+ lower than 20/μL, the CD34+ percentage was a more reliable predictor of stem cell harvest in the following days than CD34+ absolute count. Upon definition of the best CD34+ cut-off value for identification of poor-mobilizing patients, an algorithm was set up to guide plerixafor administration. It was prospectively validated in 20 patients in 2013 with encouraging results in terms of low incidences of both mobilization failure and plerixafor use. Large prospective trials that define the most cost-effective strategy for just-in-time rescue plerixafor are warranted.