Long-term outcome of patients receiving haematopoietic allogeneic stem cell transplantation as first transplant for high-risk Hodgkin lymphoma: a retrospective analysis from the Lymphoma Working Party-EBMT.

We analysed long-term outcome of patients receiving haematopoietic allogeneic stem cell transplantation (allo-HSCT) as a first transplant for high-risk Hodgkin lymphoma (HL). One hundred and ninety patients were included in this study, 63% of them had previously received brentuximab vedotin and/or checkpoint inhibitors. Seventy patients (37%) received an unrelated donor allo-HSCT, 99 (51%) had myeloablative conditioning (MAC) and 60% had in vivo T-cell/depleted grafts (TCD). The 100-day cumulative incidence (CI) of grade II-IV acute graft-versus-host disease (GVHD) was 25% and the 3-year CI of chronic GVHD was 38%. The 3-year CI of non-relapse mortality (NRM) and relapse rate were 21% and 38% respectively. After a median follow-up of 58 months, 3-year overall survival (OS) and progression-free survival (PFS) were 58% and 41% respectively. Multivariate analysis showed that, in comparison to reduced-intensity conditioning regimens with or without TCD, MAC using TCD had similar NRM and a lower risk of relapse leading to significantly better OS and PFS. MAC without TCD was associated with higher NRM and worse survival outcomes. These results suggest that in patients with high-risk HL and candidates of allo-HSCT, a MAC strategy with TCD might be the best option.

Efficacy of bortezomib to intensify the conditioning regimen and the graft-versus-host disease prophylaxis for high-risk myeloma patients undergoing transplantation.

This multicenter phase I trial was designed to evaluate the safety and efficacy of bortezomib (Bz) as part of both the conditioning regimen and the graft-versus-host disease (GvHD) prophylaxis. Patients received fludarabine, melphalan and Bz (days -9 and -2). GVHD prophylaxis consisted of Bz (days +1, +4, and +7), sirolimus (Siro) from day -5 and tacrolimus (Tk) from -3 (except the first five patients that did not receive Tk). Twenty-five patients with poor prognostic multiple myeloma were included. Eleven out of the 19 patients had high-risk features. Out of the 21 patients evaluable at day +100, 14 were in CR (67%) and 7 (33%) in PR. Cumulative incidence (CI) of nonrelapse mortality at 1 year was 24%. CI of grades 2-4 and 3-4 acute GvHD was 35% and 10%, respectively; CI of chronic GvHD was 35% and 55% at 1 and 2 years, respectively. Overall and event free survival at 2 years were 64% and 31%, respectively. Bz as part of the conditioning regimen and in the combination with Siro/tacrolimus for GvHD prophylaxis is safe and effective allowing an optimal disease control early after transplant and reducing the risk of GvHD.

Tacrolimus plus sirolimus with or without ATG as GVHD prophylaxis in HLA-mismatched unrelated donor allogeneic stem cell transplantation.

HLA-matched related or unrelated donors are not universally available. Consequently, patients can be offered hematopoietic stem cell transplantation (HSCT) from alternative donors, including mismatched unrelated donors (MMURD), known to cause a higher incidence of acute GVHD (aGVHD) and chronic GVHD. In vivo T-cell-depletion strategies, such as antithymocyte globulin (ATG) therapy, significantly decrease the risk of GVHD. We performed a multicenter, retrospective study comparing tacrolimus (TAC) and sirolimus (SIR) with or without ATG in 104 patients (TAC-SIR=45, TAC-SIR-ATG=59) who underwent MMURD HSCT. Use of ATG was associated with a lower incidence, albeit not statistically significant, of grades 2-4 aGVHD (46% vs 64%, P=0.09), no difference in grades 3-4 aGVHD (10% vs 15%, P=0.43), a trend for a lower incidence of moderate/severe chronic GVHD (16% vs 37%, P=0.09) and more frequent Epstein-Barr virus reactivation (54% vs 18%, P=0.0002). There were no statistically significant differences in 3-year overall survival (OS) (TAC-SIR-ATG=40% (95% confidence interval (CI)=24-56%) vs TAC-SIR=54% (95% CI=37-70%), P=0.43) or 3-year cumulative incidence of relapse/progression (TAC-SIR-ATG=40% (95% CI=28-58%) vs TAC-SIR=22% (95% CI=13-39%), P=0.92). An intermediate Center for International Blood & Marrow Transplant Research disease risk resulted in a significantly lower non-relapse mortality and better OS at 3 years. Our study suggests that addition of ATG to TAC-SIR in MMURD HSCT does not affect OS when compared with TAC-SIR alone.

Fludarabine/Busulfan versus Fludarabine/Melphalan Conditioning in Patients Undergoing Reduced-Intensity Conditioning Hematopoietic Stem Cell Transplantation for Lymphoma.

There is at present little data to guide the choice of conditioning for patients with lymphoma undergoing reduced-intensity conditioning (RIC) allogeneic stem cell transplantation (SCT). In this study, we compared the outcomes of patients undergoing RIC SCT who received fludarabine and melphalan (FluMel), the standard RIC regimen used by the Spanish Group of Transplantation, and fludarabine and busulfan (FluBu), the standard RIC regimen used by the Dana-Farber Cancer Institute/Brigham and Women's Hospital. We analyzed 136 patients undergoing RIC SCT for lymphoma with either FluBu (n = 61) or FluMel (n = 75) conditioning between 2007 and 2014. Median follow-up was 36 months. The cumulative incidence of grades II to IV acute graft-versus-host disease (GVHD) was 13% with FluBu and 36% with FluMel (P = .002). The cumulative incidence of nonrelapse mortality (NRM) at 1 year was 3.3% with FluBu and 31% with FluMel (P < .0001). The cumulative incidence of relapse at 1 year was 29% with FluBu and 10% with FluMel (P = .08). The 3-year disease-free survival rate was 47% with FluBu and 36% with FluMel (P = .24), and the 3-year overall survival rate was 62% with FluBu and 48% with FluMel (P = .01). In multivariable analysis, FluMel was associated with a higher risk of acute grades II to IV GVHD (HR, 7.45; 95% CI, 2.30 to 24.17; P = .001) and higher risk of NRM (HR, 4.87; 95% CI, 1.36 to 17.44; P = .015). The type of conditioning was not significantly associated with relapse or disease-free survival in multivariable models. However, conditioning regimen was the only factor significantly associated with overall survival: FluMel conditioning was associated with a hazard ratio for death of 2.78 (95% CI, 1.23 to 6.27; P = .014) compared with FluBu. In conclusion, the use of FluBu as conditioning for patients undergoing SCT for lymphoma was associated with a lower risk of acute GVHD and NRM and improved overall survival when compared with FluMel in our retrospective study. These results confirm the differences between these RIC regimens in terms of toxicity and efficacy and support the need for comparative prospective studies.

Busulfan-based reduced intensity conditioning regimens for haploidentical transplantation in relapsed/refractory Hodgkin lymphoma: Spanish multicenter experience.

Relapsed or refractory Hodgkin lymphoma (advanced HL) still remains a therapeutic challenge. Recently, unmanipulated haploidentical related donor transplant with reduced conditioning regimen (HAPLO-RIC) and post-transplant cyclophosphamide (PT-Cy) as GvHD prophylaxis has became a promising rescue strategy potentially available to almost every patient. This paper reports our multicenter experience using an IV busulfan-based HAPLO-RIC regimen and PT-Cy in the treatment of 43 patients with advanced HL. Engraftment occurred in 42 patients (97.5%), with a median time to neutrophil and platelet recovery of 18 and 26 days. Cumulative incidences of grades II-IV acute GvHD and chronic GvHD were 39% and 19%, respectively. With a median follow-up of 25.5 months for survivors, 27 patients are alive, with 22 of them disease free. Cumulative incidences of 1-year non-relapse mortality and relapse at 2 years were 21% and 24%, respectively. The estimated 2-year event-free survival (EFS) and overall survival (OS) were 48% and 58%, respectively. CR prior to HAPLO-RIC correlated with better EFS (78.5% vs 33.5%; P=0.015) and OS (86% vs 46%; P=0.044). Our findings further confirm prior reports using HAPLO-RIC in advanced HL in a multicenter approach employing an IV busulfan-based conditioning regimen.

Potential protective effect of Helicobacter pylori on the development of gastrointestinal GvHD.

Previous reports ascribe a modulating capacity of the immune response to Helicobacter pylori (HP). Our hypothesis was to demonstrate in a prospective study that HP infection could have a protective effect against development of gastrointestinal GvHD in patients receiving allogeneic hematopoietic cell transplantation (HCT). Presence of HP before transplant was determined using C(13) urea breath test. Seventy-nine patients receiving an allogeneic HCT were included and 93.7% of them received PBSC; in 51.9%, the donor was unrelated. Acute gastrointestinal GvHD was diagnosed in 51.9% (n=41). In the multivariable analysis, HP infection was associated with a lower frequency of gastrointestinal GvHD (odds ratio (OR)=0.19 (95% confidence interval (CI): 0.05-0.67); in contrast, an unrelated donor was associated with a higher frequency of gastrointestinal GvHD (odds ratio=5.4 (95% confidence interval: 1.6-18.2). One year overall survival (OS) was 74%. In the multivariate Cox proportional-hazards regression analysis, stages 0-II gastrointestinal GvHD (hazards ratio (HR)=0.19), reduced intensity conditioning (HR=0.04) and tacrolimus-sirolimus GvHD prophylaxis (HR=0.06) were all associated with a better OS. In summary, HP infection could have a role in decreasing gastrointestinal GvHD in patients receiving allogeneic HCT from peripheral blood including related and unrelated donors.

Influence of donor age in allogeneic stem cell transplant outcome in acute myeloid leukemia and myelodisplastic syndrome.

The impact of donor age in patients with acute myeloid leukemia and myelodysplastic syndrome who underwent allogeneic hematopoietic stem cell transplant (HSCT) remains unclear. In the current study, we evaluate 179 consecutive patients who received an HSCT, from January 2000 to January 2013, in our Institution. Most of the HSCT (91%) were HLA-matched. Patient and donor median age were 51 years (18-69) and 47 years (12-75) respectively, and 81 donors (45%) were older than 50 years. The median follow-up was 38 months (range 1-138), Kaplan-Meier estimated 3-year overall survival (OS) was 63% and disease free survival (DFS) was 56%. Interestingly, patients who received an HSCT from a donor older age (>50 y) showed a poorer OS (51% vs 73%; p=0.01), as well as a higher TRM (20% vs 8%; p=0.038) and higher relapse rate (28% vs 39%; p=0.03). In a stratified subanalysis, 3-year estimated OS was significantly lower among patients undergoing an HSCT from >50 years sibling donors compared to those receiving an HSCT from <50 years unrelated donor (54% vs 72%; p<0.001). In summary, we can conclude that receiving an HSCT from a donor over 50 years old is associated with poorer outcome in patients diagnosed with MDS and AML, and this information may be incorporated into the complex process of donor selection.

Comparison of upfront tandem autologous-allogeneic transplantation versus reduced intensity allogeneic transplantation for multiple myeloma.

We performed a retrospective analysis of the European Group for Blood and Marrow Transplantation database comparing the outcomes of multiple myeloma patients who received tandem autologous followed by allogeneic PSCT (auto-allo) with the outcomes of patients who underwent a reduced intensity conditioning allograft (early RIC) without prior autologous transplant. From 1996 to 2013, we identified a total of 690 patients: 517 patients were planned to receive auto-allo and 173 received an early RIC allograft without prior autologous transplant. With a median follow-up of 93 months, 5-year PFS survival was significantly better in the auto-allo group, 34% compared with 22% in the early RIC group (P<0.001). OS was also significantly improved in the auto-allo group with a 5-year rate of 59% vs 42% in the early RIC group (P=0.001). The non-relapse mortality rate was lower in the auto-allo group than in the early RIC group, with 1- and 3-year rates of 8% and 13% vs 20% and 28%, respectively (P<0.001). The relapse/progression rate was similar in the two groups, with 5-year rates of 50% for auto-allo and 46% for early RIC (P=0.42). These data suggest that planned tandem autologous allograft can improve overall survival compared with upfront RIC allograft alone in patients with multiple myeloma.

In vivo murine model of acquired resistance in myeloma reveals differential mechanisms for lenalidomide and pomalidomide in combination with dexamethasone.

The development of resistance to therapy is unavoidable in the history of multiple myeloma patients. Therefore, the study of its characteristics and mechanisms is critical in the search for novel therapeutic approaches to overcome it. This effort is hampered by the absence of appropriate preclinical models, especially those mimicking acquired resistance. Here we present an in vivo model of acquired resistance based on the continuous treatment of mice bearing subcutaneous MM1S plasmacytomas. Xenografts acquired resistance to two generations of immunomodulatory drugs (IMiDs; lenalidomide and pomalidomide) in combination with dexamethasone, that was reversible after a wash-out period. Furthermore, lenalidomide-dexamethasone (LD) or pomalidomide-dexamethasone (PD) did not display cross-resistance, which could be due to the differential requirements of the key target Cereblon and its substrates Aiolos and Ikaros observed in cells resistant to each combination. Differential gene expression profiles of LD and PD could also explain the absence of cross-resistance. Onset of resistance to both combinations was accompanied by upregulation of the mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK)/ERK pathway and addition of selumetinib, a small-molecule MEK inhibitor, could resensitize resistant cells. Our results provide insights into the mechanisms of acquired resistance to LD and PD combinations and offer possible therapeutic approaches to addressing IMiD resistance in the clinic.

GVHD prophylaxis with sirolimus-tacrolimus may overcome the deleterious effect on survival of HLA mismatch after reduced-intensity conditioning allo-SCT.

Large studies, mostly based on series of patients receiving CSA/tacrolimus (TKR) plus MTX as immunoprophylaxis, have demonstrated a deleterious effect on survival of the presence of a single mismatch out of eight loci after allogeneic hematopoietic SCT (alloHSCT). We retrospectively analyzed a series of 159 adult patients who received sirolimus(SRL)/TKR prophylaxis after alloHSCT. We compared overall outcomes according to HLA compatibility in A, B, C and DRB1 loci at the allele level: 7/8 (n=20) vs 8/8 (n=139). Donor type was unrelated in 95% vs 70% among 7/8 vs 8/8 pairs, respectively (P=0.01). No significant differences were observed in 3-year OS (68 vs 62%), 3-year EFS (53 vs 49%) and 1-year non-relapse mortality (9 vs 13%). Cumulative incidence of grades II-IV acute GVHD (aGVHD) was significantly higher in 7/8 alloHSCT (68% vs 42%, P<0.001) but no significant differences were found for III-IV aGVHD (4.5% vs 11%), overall (35% vs 53%) and extensive (20% vs 35%) chronic GHVD in 7/8 vs 8/8 subgroups, respectively. In summary, the present study indicates favorable outcomes after alloHSCT using the combination of SRL/TKR combination as GVHD prophylaxis with OS in the range of 55-70%, and non-significant differences in overall outcomes, irrespective of the presence of any mismatches at obligatory loci.

Comparing i.v. BU dose intensity between two regimens (FB2 vs FB4) for allogeneic HCT for AML in CR1: a report from the Acute Leukemia Working Party of EBMT.

This retrospective analysis compared two regimens of fludarabine combined with i.v. BU 6.4 mg/kg (FB2) or BU 12.8 mg/kg (FB4) for allografting of AML in first CR. A total of 437 patients (median age: 50 years) were administered FB2 (n = 225, 51%) or FB4 (n = 212, 49%). Median follow-up time was 28 months. Use of FB2 resulted in a longer time to neutrophil engraftment (17 vs 15 days, P < 0.0001) but no difference in incidence of grade II-IV acute (P = 0.54) or chronic GVHD (P = 0.51). In patients < 50 years of age, FB2 was associated with a higher 2-year cumulative incidence of relapse (33 ± 6% vs 20 ± 4%, P = 0.04), but there was no difference in 2-year leukemia-free survival (LFS) (P = 0.45), OS (P = 0.53) or non-relapse mortality (P = 0.17). In recipients ⩾ 50 years of age, FB2 resulted in better 2-year LFS (63 ± 4% vs 42 ± 7%, P = 0.02) and OS (68 ± 4% vs 45 ± 7%, P = 0.006); a lower 2-year non-relapse mortality, albeit not statistically significant (15 ± 3% vs 29 ± 6%, P = 0.06), was observed with FB2. FB2 is an effective and well-tolerated regimen in patients ⩾ 50 years of age and does not compromise survival when used in patients <50 years undergoing allogeneic transplantation for AML in first CR.

Risk factors for thrombotic microangiopathy in allogeneic hematopoietic stem cell recipients receiving GVHD prophylaxis with tacrolimus plus MTX or sirolimus.

Transplantation-associated thrombotic microangiopathy (TA-TMA) is a feared complication of allogeneic hematopoietic SCT (HSCT) owing to its high mortality rate. The use of calcineurin inhibitors or sirolimus (SIR) for GVHD prophylaxis has been suggested as a potential risk factor. However, the impact of tacrolimus (TAC) and SIR combinations on the increased risk of TA-TMA is currently not well defined. We retrospectively analyzed the incidence of TA-TMA in 102 allogeneic HSCT recipients who consecutively received TAC plus SIR (TAC/SIR) (n=68) or plus MTX (TAC/MTX)±ATG (n=34) for GVHD prophylaxis. No significant differences were observed in the incidence of TA-TMA between patients receiving TAC/SIR vs TAC/MTX±ATG (7.4% vs 8.8%, P=0.8). Only grade III-IV acute GVHD, previous HSCT and serum levels of TAC >25 ng/mL were associated with a greater risk of TA-TMA. Patients developing TA-TMA have significantly poorer survival (P<0.001); however, TA-TMA ceased to be an independent prognostic factor when it was included in a multivariate model. In conclusion, the combination of TAC/SIR does not appear to pose a higher risk of TA-TMA. By contrast, we identified three different risk groups for developing TA-TMA.

Impact of in vivo T-cell depletion on outcome of AML patients in first CR given peripheral blood stem cells and reduced-intensity conditioning allo-SCT from a HLA-identical sibling donor: a report from the Acute Leukemia Working Party of the European Group for Blood and Marrow Transplantation.

The impact of in vivo T-cell depletion on transplantation outcomes in patients transplanted with reduced-intensity conditioning (RIC) remains controversial. This study assessed the outcome of 1250 adult patients with de novo AML in first CR (CR1) given PBSC from HLA-identical siblings after chemotherapy-based RIC. A total of 554 patients did not receive any form of in vivo T-cell depletion (control group), whereas antithymocyte globulin (ATG) and alemtuzumab were given in 444 and 252 patients, respectively. The incidences of grade II-IV acute GVHD were 21.4, 17.6 and 10.2% in control, ATG and alemtuzumab patients, respectively (P<0.001). In multivariate analysis, the use of ATG and the use of alemtuzumab were each associated with a lower risk of chronic GVHD (P<0.001 each), but a similar risk of relapse, and of nonrelapse mortality, and similar leukemia-free survival and OS. Further, among patients given BU-based RIC, the use of <6 mg/kg ATG did not increase the risk of relapse (hazard ratio, HR=1.1), whereas there was a suggestion for higher relapse risk in patients given 6 mg/kg ATG (HR=1.4, P=0.08). In summary, these data suggest that a certain amount of in vivo T-cell depletion can be safely used in the conditioning of AML patients in CR1 given PBSC after chemotherapy-based RIC.

SNP-based mapping arrays reveal high genomic complexity in monoclonal gammopathies, from MGUS to myeloma status.

Genetic events mediating transformation from premalignant monoclonal gammopathies (MG) to multiple myeloma (MM) are unknown. To obtain a comprehensive genomic profile of MG from the early to late stages, we performed high-resolution analysis of purified plasma cells from 20 MGUS, 20 smoldering MM (SMM) and 34 MM by high-density 6.0 SNP array. A progressive increase in the incidence of copy number abnormalities (CNA) from MGUS to SMM and to MM (median 5, 7.5 and 12 per case, respectively) was observed (P=0.006). Gains on 1q, 3p, 6p, 9p, 11q, 19p, 19q and 21q along with 1p, 16q and 22q deletions were significantly less frequent in MGUS than in MM. Although 11q and 21q gains together with 16q and 22q deletions were apparently exclusive of MM status, we observed that these abnormalities were also present in minor subclones in MGUS. Overall, a total of 65 copy number-neutral LOH (CNN-LOH) were detected. Their frequency was higher in active MM than in the asymptomatic entities (P=0.047). A strong association between genetic lesions and fragile sites was also detected. In summary, our study shows an increasing genomic complexity from MGUS to MM and identifies new chromosomal regions involved in CNA and CNN-LOH.

Incidence, characteristics and risk factors of marked hyperbilirubinemia after allogeneic hematopoietic cell transplantation with reduced-intensity conditioning.

To analyze the incidence, characteristics and risk factors of hyperbilirubinemia after allogeneic hematopoietic cell transplantation with reduced-intensity conditioning (allo-RIC), we conducted a retrospective study in three Spanish centers. We analyzed 452 consecutive patients receiving allo-RIC. Of these, 92 patients (20%) developed marked hyperbilirubinemia (>4 mg/day or >68.4 µM) after allo-RIC. The main causes of marked hyperbilirubinemia after transplant were cholestasis due to GVHD or sepsis (n=57, 62%) and drug-induced cholestasis (n=13, 14%). A total of 22 patients with marked hyperbilirubinemia (24%) underwent liver biopsy. The most frequent histological finding was iron overload alone (n=6) or in combination with other features (n=6). In multivariate analysis, the risk factors for marked hyperbilirubinemia after allo-RIC were non-HLA-identical sibling donors (hazard ratio (HR) 2.2 (95% confidence interval (CI) 1.4-3.6) P=0.001), female donors to male recipients (HR 2.1 (95% CI 1.3-3.3) P=0.003) and high levels of bilirubin and γ-glutamyl transpeptidase before transplant (HR 4.5 (95% CI 2.5-8.4) P<0.001 and HR 4.6 (95% CI 2.6-8.1) P<0.001, respectively). Patients with marked hyperbilirubinemia showed higher 4-year nonrelapse mortality (HR 1.3 (95% CI 1-1.7), P=0.02) and lower 4-year OS (HR 1.4 (95%CI 1.3-1.7), P<0.001) than patients without. In conclusion, we confirm that marked hyperbilirubinemia is frequent and diverse after allo-RIC. Development of marked hyperbilirubinemia after allo-RIC is associated with worse outcome of the procedure.

Clinical significance of CD81 expression by clonal plasma cells in high-risk smoldering and symptomatic multiple myeloma patients.

The presence of CD19 in myelomatous plasma cells (MM-PCs) correlates with adverse prognosis in multiple myeloma (MM). Although CD19 expression is upregulated by CD81, this marker has been poorly investigated and its prognostic value in MM remains unknown. We have analyzed CD81 expression by multiparameter flow cytometry in MM-PCs from 230 MM patients at diagnosis included in the Grupo Español de Mieloma (GEM)05>65 years trial as well as 56 high-risk smoldering MM (SMM). CD81 expression was detected in 45% (103/230) MM patients, and the detection of CD81(+) MM-PC was an independent prognostic factor for progression-free (hazard ratio=1.9; P=0.003) and overall survival (hazard ratio=2.0; P=0.02); this adverse impact was validated in an additional series of 325 transplant-candidate MM patients included in the GEM05 <65 years trial. Moreover, CD81(+) SMM (n=34/56, 57%) patients had a shorter time to progression to MM (P=0.02). Overall, our results show that CD81 may have a relevant role in MM pathogenesis and represent a novel adverse prognostic marker in myeloma.

Competition between clonal plasma cells and normal cells for potentially overlapping bone marrow niches is associated with a progressively altered cellular distribution in MGUS vs myeloma.

Disappearance of normal bone marrow (BM) plasma cells (PC) predicts malignant transformation of monoclonal gammopathy of undetermined significance (MGUS) and smoldering myeloma (SMM) into symptomatic multiple myeloma (MM). The homing, behavior and survival of normal PC, but also CD34(+) hematopoietic stem cells (HSC), B-cell precursors, and clonal PC largely depends on their interaction with stromal cell-derived factor-1 (SDF-1) expressing, potentially overlapping BM stromal cell niches. Here, we investigate the distribution, phenotypic characteristics and competitive migration capacity of these cell populations in patients with MGUS, SMM and MM vs healthy adults (HA) aged >60 years. Our results show that BM and peripheral blood (PB) clonal PC progressively increase from MGUS to MM, the latter showing a slightly more immature immunophenotype. Of note, such increased number of clonal PC is associated with progressive depletion of normal PC, B-cell precursors and CD34(+) HSC in the BM, also with a parallel increase in PB. In an ex vivo model, normal PC, B-cell precursors and CD34(+) HSC from MGUS and SMM, but not MM patients, were able to abrogate the migration of clonal PC into serial concentrations of SDF-1. Overall, our results show that progressive competition and replacement of normal BM cells by clonal PC is associated with more advanced disease in patients with MGUS, SMM and MM.