P1343: transplant outcomes of lymphoma patients undergoing stem cell mobilization with plerixafor

Background: Autologous stem cell transplantation is a standard treatment modality widely used in relapsed refractory Hodgkin and Non-Hodgkin Lymphoma. In order to perform an autologous stem cell transplantation, it is necessary to collect sufficient stem cells. The accepted minimal number of stem cells that will provide the reconstruction of hematopoiesis after high-dose chemotherapy is >2x106/kg CD34(+), and the optimal number is >5x106/kg CD34(+) stem cells. Aims: In this study, we aimed to compare the engraftment kinetics and long-term survival data after autologous stem cell transplantation in lymphoma patients who underwent stem cell mobilization with plerixafor. Methods: Between 2006 and 2020, 138 lymphoma patients who underwent autologous stem cell transplantation in our clinic were retrospectively analyzed. The last follow-up and survival data of the patients were obtained in January 2022. First-line peripheral stem cell mobilization with chemotherapy+G-CSF (5-10 μg/kg/day) was planned for all patients. Patients whom were mobilized at least 2x106/kg CD34(+) stem cells with this regimen were defined as “good mobilizers”. Patients who could not be mobilized with chemotherapy + G-CSF in the first line were mobilized with Plerixafor + G-CSF who could collect at least 2x106/kg CD34(+) stem cells with this collection regimen was defined as “poor mobilizers”. Results: While 110 of the patients (79.8%) were considered as “good mobilizers”, 28 patients (20.2%) took place in the “poor mobilizer” group. The mean age was 37.6 years in the good mobilizer group, while the mean age was 48.3 years in the poor mobilizer group.The good mobilizers group were significantly younger than poor mobilizer group (p<0.001). There was no significant difference between the two groups in terms of gender, histological diagnosis, stage, presence of B symptoms, bone marrow involvement, Bulky disease, prior chmo lines, disease status at the time of transplant, and ECOG performance score. The amount of collected and infused stem cells in the poor mobilizers group was significantly lower than in the good mobilzers arm (4.54x106/kg vs 3.6 x106/kg, p<0.001). While no significant difference was observed in the median neutrophil engrafment day(11 vs 10 day, p=0.06), median platellet engrafment day was significantly longer in the poor mobilizers group (12 vs 13 day, p=0.011). After a median 38 month follow up time; The 5-year progression-free survival rate was 49.7% in the good mobilizers arm and 48.6% in the poor mobilizers arm, with a median PFS of 73 months in the good mobilizers arm and 59 months in the poor mobilizers arm, and no significant difference was found between the two groups in terms of PFS. (p=0.912).The 5-year Overall Survival was 62.1% in the good mobilizers arm and 58.5% in the poor mobilizers arm with a median OS was not reached in the good mobilizers arm, the median OS was 83 months in the poor mobilziers group. There was no significant difference in overall survival between the two groups (p=0.748) Image:Summary/Conclusion: In our study, no difference was found between poor mobilizers and good mobilizers in terms of progression-free survival and overall survival. However, the amount of mobilized stem cells were lesser and the median platelet engraftment day was longer in the poor mobilizers arm. We conclude that plerixafor administration is safe and efficient for mobilization in lymphoma patients who were poor mobilizers.