Stem cell mobilization in multiple myeloma patients relapsing after previous autologous hematopoietic stem cell transplantation: A multicenter report by the Polish Myeloma Study Group.

Background: Salvage autologous hematopoietic stem cell transplantation (autoHSCT) may be used to treat relapse of multiple myeloma occurring after previous autoHSCT. When insufficient number of hematopoietic stem cells was stored from the initial harvest, remobilization of stem cells is necessary.

Purpose: The analysis of stem cell remobilization after previous autoHSCT.

Patients And Methods: Fifty-eight patients, 60% males, median 59 years, were included. Median time interval between autoHSCT and remobilization was 42 months. The first remobilization was performed mostly after chemotherapy: cyclophosphamide (33%), cytarabine (43%), and etoposide (19%).

Results: The first remobilization was successful in 67% patients. About 19% patients required plerixafor rescue, among whom it allowed for successful harvesting in 14%. Use of cyclophosphamide, cytarabine, and etoposide allowed for successful remobilization in 53%, 84%, and 55% patients, respectively. Patients treated with cytarabine had the highest yield of CD34+ cells (median 7.5 × 10 /kg vs 5.8 and 2.4 for etoposide and cyclophosphamide, P = .001). Higher percentage of patients was able to collect ≥2 × 10 CD34+ cells/kg during one leukapheresis after cytarabine (76% vs 21% for cyclophosphamide vs 36% for etoposide, P = .001). Cytarabine use was associated with lower risk of remobilization failure OR = 0.217, P = .02. Toxicity comprised mostly hematological toxicity (thrombocytopenia and neutropenia). One patient succumbed to septic shock.

Conclusion: Remobilization after previous autoHSCT is feasible only in a proportion of patients. Cytarabine is associated with the highest rate of successful mobilization and the highest yield of mobilized CD34+ cells. The toxicity requires careful surveillance of these patients.