Targeting the Poor Mobilizing Population of Patients for An Autologous Transplantation Procedure: A Single Centre Experience

Peripheral blood (PB) has become the major source of hematopoietic stem cells for autologous stem cell transplantation (ASCT) in the last 15–20 years. Nevertheless, there is a subset of patients who do not mobilize adequate numbers of CD34+ cells. There are no clearly established guidelines with respect to second-line mobilization protocols. The aim of this study has been to analyze our experience as a single center with this population of poor mobilizers trying to identify clinical or biological adverse prognostic factors associated to a poor mobilization of progenitor cells into PB, results of second- and third-line mobilization procedures and outcome after the ASCT of those patients who could be autografted in terms of hematological recovery. Poor mobilizing patients were defined as those in whom the apheresis procedure could not be started because of < 10 CD34⁺ cells/ul or those in which a less than 2 × 10⁶ CD34⁺ cells/kg could be collected in the first mobilization attempt. From January/2000 to January/2008, 126 patients [70 males/56 females, median age of 53 years (range, 20–70)] out of a total number of 450 patients mobilized for an ASCT in our institution (28%) were identified as poor mobilizers. Clinical diagnosis were: 29 multiple myeloma, 16 Hodgkin’s lymphoma, 48 non-Hodgkin’s lymphoma, 28 acute leukemias and 5 other diagnosis. Median time from diagnosis to mobilization therapy was 19 (range, 3–120) months and median number of chemotherapy lines received before the procedure was 2 (range, 0–5). The first mobilizing protocol was G-CSF alone (5–10 ug/kg/day sc) in 72% of the patients or the combination of chemotherapy plus G-CSF in 28% of the patients. A second mobilization procedure was attempted in 34 patients (28%) with high-doses of G-CSF alone (16–20 ug/kg/day sc) in 24 patients, the combination of G-CSF plus chemotherapy in 8 patients and the combination of G-CSG with stem cell factor (SCF) in 2 patients. A third mobilization attempt was performed in 6 patients (high-doses of G-CSF alone in 4 patients, G-CSF plus chemotherapy in 1 patient and G-CSF plus SCF in 1 patient). Sixty-nine patients (54%) were finally autografted. Median number of CD34⁺ cells/kg infused were 2.15 × 10⁶/kg (range, 1.01–4.00). Median time to neutrophil recovery after transplantation was 11 days (range, 4–20). Patients with an inadequate mobilization constitute a significant clinical problem (25% of the whole population of patients with an indication of ASCT in our centre). Nevertheless, half of these patients can be rescued for an ASCT procedure with one or two more attempts. Neutrophil recovery after the autologous transplant in those patients undergoing the procedure seems to be similar to that of the group of patients with an adequate first mobilization attempt. New mobilizing agents should be investigated in order to increase the efficacy of the mobilization processes.