P1316: increased efficacy of intermediate-dose arac+g-csf compared to cy+g-csf and plerixafor+g-csf as a stem cell mobilization regimen in poor mobilizers with hematological malignancies

Topic: 22. Stem cell transplantation - Clinical Background: High dose chemotherapy with autologous hematopoietic stem cell transplantation (autoHSCT) is an effective treatment option for lymphomas and multiple myeloma (MM). Peripheral blood stem cell (PBSC) is associated with faster hematological reconstitution and engraftment compared to bone marrow stem cell and preferentially used as a hematopoietic stem cell source. Despite using novel agents and improving algorithms, there are patients who fail to mobilize sufficient number of CD34+ cells. Thus, finding new approaches is still a current challenge. Aims: Based on these considerations we aimed to retrospectively assess the efficacy of Intermediate-dose (ID) AraC+G-CSF as mobilization regimen in comparison to Cy+G-CSF and Plerixafor+G-CSF in patients with hematological malignancies. Methods: A retrospective analysis was performed on 85 consecutive lymphoma and MM patients who met at least one criterion of “predicted poor mobilizers” according to classification proposed by Gruppo Italiano Trapianto di Midollo Osseo [1]. (Table 1)From April 2019 to August 2022 patients were mobilized either with ID-AraC+G-CSF or Cy+G-CSF or Plerixafor+G-CSF. Ara-C was administered at a dose of 0.4 g/m2 twice daily on days 1 and 2 (total dose 1.6 g/m2) plus G-CSF 10 mg/kg/day from day 7 until the end of PBSC collection. Cy was administered at a dose of 2-4 g/m2 on day 1 plus G-CSF 10 mg/kg/day from day 5 until the end of PBSC collection. Plerixafor was given at a dose of 0.24 mg/kg/day from day 5 of treatment with G-CSF 10 mg/kg/day. The apheresis procedure was started when CD34+ cells reached 20×106/L in peripheral blood. The target CD34+ cell yield of 2.0×106 CD34+/kg for lymphoma patients and 4×106 CD34+/kg for MM patients. Results: Peak concentrations of circulating CD34+ cells in peripheral blood were significantly higher in ID-AraC+G-CSF (median 153, IQR 106-334) compared to Cy+G-CSF (median 129, IQR 74-355) and Plerixafor+G-CSF (median 33, IQR 28-39, p=0.005). The median number of collected CD34+ cells was also higher in patients mobilized with ID-AraC+G-CSF (10.2, IQR 5.2-16.9) vs with Cy+G-CSF (7.2, IQR 4.4-9.9) or Plerixafor+G-CSF (2.5, IQR 1.4-4.0, p<0.0001). A single apheresis was sufficient to collect the target number of CD34+ cells in 96% patients in the Ara-C group compared to 46% in the Cy group and 76% in the Plerixafor group (p<0.0001). Summary/Conclusion: Intermediate dose AraC+G-CSF is more effective for stem cell mobilization than Cy+G-CSF or Plerixafor+G-CSF in patients who are at risk of mobilization failure. ID-AraC could be a preferable mobilization regimen in this setting. Reference [1] Olivieri, A., Marchetti, M., Lemoli, R. et al. Proposed definition of ‘poor mobilizer’ in lymphoma and multiple myeloma: an analytic hierarchy process by ad hoc working group Gruppo ItalianoTrapianto di Midollo Osseo. Bone Marrow Transplant47, 342–351 (2012). https://doi.org/10.1038/bmt.2011.82 Keywords: Ara-C (cytarabine), Peripheral blood stem cell mobilization, Autologous hematopoietic stem cell transplantation