Outcomes of upfront plerixafor use for mobilization in germ cell tumor patients

High-dose chemotherapy with autologous hematopoietic stem cell transplantation (auto-HSCT) improved 5-year overall survival rates in relapsed/refractory germ cell tumors (GCTs) from 10% to 52%. Nearly 30% of GCT patients are deemed poor mobilizers after receiving several lines of prior therapy. There is limited data available regarding upfront plerixafor use in GCT patients. We predicted upfront plerixafor use would increase the amount of stem cells collected preventing subsequent mobilizations and improve time to curative therapy. A retrospective, single center, chart review of adult GCT patients who received plerixafor upfront for mobilization at a single center between January 1, 2013 and August 31, 2021 was performed. The primary objective was to evaluate the rate of successful peripheral blood CD34⁺ cell collections. Secondary objectives consisted of describing the impact of plerixafor use on mobilization and assessing auto-HSCT related outcomes. Sixteen patients received plerixafor upfront after an average of three prior lines of therapy (range: 2-5 lines). Successful collection (≥4 × 10⁶ CD34⁺ cells/Kg collected within four days) was achieved in 15 (94%) patients in a median of one apheresis day (interquartile range: 1-2 days). All patients proceeded to an initial auto-HSCT and 12 patients (75%) completed both transplants as planned. Survival at 12 months was 50%. The significantly higher amount of CD34⁺ cells collected over less apheresis days demonstrated the clinical utility of upfront plerixafor and its potential to facilitate more efficient stem cell mobilization. There is a need for larger randomized studies with upfront plerixafor use in this unique patient population.