Optimal infused CD34+ cell dose in multiple myeloma patients undergoing upfront autologous hematopoietic stem cell transplantation

Abstract

Abstract Autologous transplantation remains the standard of care for eligible multiple myeloma (MM) patients, yet optimal CD34+ cell dose remains unclear. We conducted a retrospective study on MM patients undergoing upfront transplant between 2005 and 2021 and divided them into low (≤2.5 × 106 cells/kg) and high (>2.5 × 106 cells/kg) CD34+ dose groups. We included 2479 patients, 95 in the low CD34+ group and 2384 in the high CD34+ group. Patients in the low CD34+ group were older (63.2 vs 61.1 years, p = 0.013), more often had R-ISS III (19% vs 9%, p = 0.014), received plerixafor (60% vs 35%, p 2.5 × 106 cells/kg. Multivariable analysis affirmed that CD34+ >2.5 × 106 cells/kg was associated with better PFS (HR 0.71, p = 0.008) and OS (0.59, p 2.5 × 106 cells/kg remained a predictor of better OS (0.42, p 2.5 × 106 cells/kg was associated with improved survival, without any additional benefit at incrementally higher doses.