Autologous STEM Cell Collection after Daratumumab, Bortezomib, Thalidomide and Dexamethasone Versus Bortezomib, Thalidomide and Dexamethasone in NEWLY Diagnosed Multiple Myeloma: A Real-Life Monocentric Italian Experience

Introduction In newly diagnosed multiple myeloma (NDMM) patients (pts), induction followed by high-dose chemotherapy and autologous stem cell transplantation (ASCT) remains the standard of care. The addition of an anti-CD38 antibody, daratumumab, to an established frontline protocol based on bortezomib, thalidomide and dexamethasone (D-VTd), improves efficacy but could hamper peripheral blood stem cell collection (PBCS). Methods The aim of our study is to evaluate the possible impact of the addition of daratumumab to induction therapy prior to ASCT on PBCS and hospitalization parameters a real-world population with NDMM. We hereby, retrospectively analyzed 28 NDMM pts who received 6 cycles of D-VTd as induction therapy before ASCT and compared them with a consecutive series of 32 VTD-treated NDMM pts who were matched for cytogenetic abnormalities and age, managed at the Hematology Department of Sapienza University in Rome. Results Patient baseline characteristics were equally distributed among both groups, as summarized in Table 1. After induction therapy, a combination of cyclophosphamide (CTX) with granulocyte colony stimulating factor (G-CSF) at standard dose of 10 mg/sqm/day was used as the first mobilizing regimen attempt in both groups. The median time between the last day of induction therapy and the first day of mobilization therapy was 30 days for D-VTd groups and 22 days for VTD groups (p=0.041). Overall, 94% of pts treated with VTd met the desired collection goal after first mobilization therapy, compared to 68% of pts treated with D-VTd (p=0.01). In the VTd arm, 1 pts required a second mobilization attempt, and 1 pts required a further one. In the D-VTd arm, 5 pts required a second mobilization attempt, and 4 pts also required a further one. Overall, 3 pts in the D-VTd arm did not meet the collection goal. In pts with impaired mobilization, plerixafor was used in 4/32 pts in the VTd arm (13%), compared to 29% of pts treated with D-VTd (p=0.195). In the D-VTd arm, 12/28 pts (43%) had received a higher dose of CTX as mobilization therapy (3 g/m 2) compared to the standard dose of 2.4 g/m 2 in 16/28 pts (57%). Nevertheless, no difference was observed in the rate of PBSC collection at the first attempt (p=0.7). No baseline clinical or disease characteristics were observed to have negative impact on the PBSC at first mobilization attempt, including treatment response at the end of induction therapy. Nevertheless, a significantly lower pre-mobilizati