Impact of Peripheral Blood Stem Cell Recruitment on Outcome of Single or Double Autologous Hematopoietic stem Cell Transplantation for Multiple Myeloma.
Authors: Michallet Mauricette , Le Quoc-Hung , Michallet Anne-Sophie , Thiebaut Anne , Tavernier Emmanuelle , Troncy Jacques , Thomas Xavier , Chelghoum Youcef , Praire Aline , Gadolet Elodie , Nicolini Franck E. , Clapisson Gilles , Philip Irene 
Published: April 2020

Abstract
Multiple myeloma remains one of the best indication for intensive chemotherapy followed by autologous hematopoietic stem cell transplantation (autoT). Intensive therapy followed by autologous transplantation is superior to conventional chemotherapy and it was demonstrated that two autoT were superior to one except for patients in very good partial response or in complete response after the first autotransplant. Peripheral blood stem cells (PBSC) can be used as well as bone marrow as HSC source with the same efficacy but very few data have been reported regarding PBSC recruitment. The main goal of our work was to study the impact on overall and event-free survival (OS and EFS) of PBSC recruitment using either growth factors (GF) alone (steady state) or chemotherapy followed by GF. Secondly, we performed a multivariate analysis studying influence on OS and EFS of sex, age, lines of therapy, pretransplant status, TBI, PBSC recruitment and number of autoT. We have analyzed 193 PBSC autoT (1 autoT=160, 2 autoT=33) performed for 160 MM patients [81 males and 71 females, mean age: 55 years (39–71)]. At diagnosis, 88 patients presented a MM Ig G (70k and 18l), 28 Ig A (16k and 12l), 3 Ig D (1k and 2l), 21 light chains k and 13 light chains l, 3 non secreting and 4 with plasmocyte leukemias. According to Durie and Salmon classification 75% of patients were in stage III, 15% in stage II and 10% in progressive I. Before transplantation, patients have received 1 line of poly-chemotherapy (n=141), 2 lines (n=15) or 3 lines (n=4) and 154 were evaluated for the response with 11 complete remission, 113 partial remission and 30 stable or evolutive disease just before transplant. As HSC (n=189), patients received PBSC which were recruited by GF alone (n=105) or cyclophosphamide+GF (n= 84). Conditioning (n=189),consisted in melphalan and TBI (n=51), melphalan alone (n=132), melphalan associated to cyclophosphamide or busulfan (n=6). We divided the population into 4 groups : group 1 who received one autoT of PBSC recruited by GF (n=76), group 2 one autoT of PBSC recruited by chemotherapy+GF (n=50), group 3 two autoT of PBSC recruited by GF (n=16) and group 4 two autoT of PBSC recruited by chemotherapy+GF (n=17). The median follow-up (FU) of the 4 groups were different with shorter FU (group 3: 9.9 months, group 4: 13 months) for patients who received tandem autoT because of the recent character of this strategy as compared to a long term follow-up for patients who received only one transplant (group 1: 35months, group 2: 55.3 months). Probabilities of OS and EFS at 2 years were 76% (95%CI 67–87) and 60% (95%CI 49.5–73) for group 1, 77% (95%CI 65–90.5) and 70% (95%CI 57.5–85) for group 2, 87.5% (95%CI 73–100) and 72.9% (95%CI 49–100) for group 3, 100% and 66.7% (95%CI 36–100) for group 4. The difference was not significant because of follow-up differences between the 4 groups and small number of patients in groups 3 and 4. In addition, multivariate analysis did not show any significant influence of the different studied parameters on OS and EFS. Nevertheless, because of these interesting preliminary results, a longer follow-up is warranted for definitive conclusions.