Purging of autologous peripheral-blood stem cells using CD34 selection does not improve overall or progression-free survival after high-dose chemotherapy for multiple myeloma: results of a multicenter randomized controlled trial

Impact of residual tumor cells in the stem cell collection on multiple myeloma patients receiving autologous stem cell transplantation

Autologous stem cell transplantation (ASCT) is the standard therapy for patients with transplant-eligible multiple myeloma (TEMM). However, the ideal depth of response required before ASCT and the impact of residual tumor cells in the stem cell collection (SCC) on survival remains unclear. Here we collected data of 89 patients with TEMM undergoing ASCT and analyzed the minimal residual disease of SCC (cMRD) and bone marrow (BM) (mMRD) before transplantation. Before ASCT, 31.5% and 76.4% of patients achieved MRD negativity in BM and SCC, respectively. Tumor cells were less in SCC samples than that in BM samples. Neoplastic cells in SCC could be observed in patients with different responses after induction therapy, and there were no significant differences in the percentage and level of cMRD among these subgroups (P > 0.05). No correlation was found between the cMRD status and the response patients achieved after ASCT (P > 0.05). The median follow-up was 26.8 months. mMRD negativity before ASCT was associated with longer PFS (55.9 vs. 27.1 months; P = 0.009) but not OS (not reached vs. 58.9 months; P = 0.115). Patients with different cMRD statuses before ASCT experienced similar PFS (40.5 vs. 76.4 months for negativity vs. positivity; P = 0.685) and OS (not reached vs. 58.8 months for negativity vs. positivity; P = 0.889). These results suggested that detectable cMRD does not significantly predict the inferior post-ASCT response or shorter survival, and patients are eligible to undergo ASCT upon achieving partial response.

Impact of clonal plasma cells in autografts on outcomes in high-risk multiple myeloma patients

Most patients with multiple myeloma (MM) undergoing autologous hematopoietic stem cell transplantation (autoHCT) eventually relapse, perhaps due to the presence of clonal plasma cells (CPC) in the autograft. We conducted a retrospective analysis to evaluate the impact of CPC in the autograft on the outcomes of high-risk chromosomal abnormalities (HRMM) patients undergoing autoHCT between 2008 and 2018. Patients were divided into CPC+ or CPC- in the autograft by next-generation flow cytometry (NGF). There were 75 CPC + autografts (18%) and 341 CPC- (82%). The CPC + group was less likely to achieve MRD-negative complete remission post-transplant (11% vs. 42%; p < 0.001). Median progression free survival (PFS) and overall survival (OS) were (12.8 vs. 32.1 months) and (36.4 vs. 81.2 months) in the CPC + and CPC- groups, respectively (both p < 0.001). Also in the subset of patients with MRD-negative ≥VGPR prior to autoHCT, those with CPC + autografts had inferior PFS (HR 4.21, p = 0.006) and OS (HR 7.04, p = 0.002) compared to CPC-. In multivariable analysis, the degree of CPC positivity in the autograft was independently predictive of worse PFS (HR 1.50, p = 0.001) and OS (HR 1.37, p = 0.001). In conclusion, both the presence and degree of CPC in the autograft were highly predictive of inferior PFS and OS.

Treatment Strategy for Ultra-High-Risk Multiple Myelomas with Chromosomal Aberrations Considering Minimal Residual Disease Status and Bone Marrow Microenvironment

Despite the development of anti-myeloma therapeutics, such as proteasome inhibitors, immunomodulatory drugs, anti-CD38 monoclonal antibodies, and autologous stem cell transplantation (ASCT), multiple myeloma remains incurable. A trial treatment combining four drugs-daratumumab, carfilzomib, lenalidomide, and dexamethasone-followed by ASCT frequently results in minimal residual disease (MRD) negativity and prevents progressive disease in patients with standard- and high-risk cytogenetics; however, it is insufficient to overcome the poor outcomes in patients with ultra-high-risk chromosomal aberration (UHRCA). In fact, MRD status in autografts can predict clinical outcomes after ASCT. Therefore, the current treatment strategy might be insufficient to overcome the negative impact of UHRCA in patients with MRD positivity after the four-drug induction therapy. High-risk myeloma cells lead to poor clinical outcomes not only by aggressive myeloma behavior but also via the generation of a poor bone marrow microenvironment. Meanwhile, the immune microenvironment effectively suppresses myeloma cells with a low frequency of high-risk cytogenetic abnormalities in early-stage myeloma compared to late-stage myeloma. Therefore, early intervention might be key to improving clinical outcomes in myeloma patients. The purpose of this review is to improve clinical outcomes in patients with UHRCA by considering MRD assessment results and improvement of the microenvironment.

Eight-color multiparameter flow cytometry (EuroFlow-NGF) is as sensitive as next-generation sequencing in detecting minimal/measurable residual disease in autografts of patients with multiple myeloma

The prognostic value of minimal/measurable residual disease (MRD) detection in autografts of patients with multiple myeloma (MM) in an autologous stem-cell transplantation setting has been reported. Next-generation flow (NGF) cytometry has lower sensitivity (2 × 10-6) to detect MRD than next-generation sequencing (NGS) (<10-6). We compared the clinical value of high-sensitivity NGF (cutoff: <10-6) and NGS (cutoff: 10-6) for the detection of MRD in the cryopreserved autografts of 49 patients with newly diagnosed MM. The sensitivity test using frozen/thawed autografts revealed a strong correlation among MRD levels of 5 × 10-7 and 1 × 10-4 (r = 0.9997, p < 0.0001) when an adequate number of cells were analyzed. Autograft MRD levels determined using NGF and NGS were highly correlated (r = 0.811, p < 0.0001). MRD-negative patients identified with NGF (cutoff: <10-6) showed significantly longer progression-free survival (PFS) than MRD-positive patients (p = 0.026). The PFS of MRD-negative patients determined by NGS (cutoff: 10-6) was similar to that determined by NGF. These results show that the high-sensitivity NGF method can assess MRD in frozen/thawed autografts, and its prognostic value is comparable to that of NGS.

Aberrant Plasma Cell Contamination of Peripheral Blood Stem Cell Autografts, Assessed by Next-Generation Flow Cytometry, Is a Negative Predictor for Deep Response Post Autologous Transplantation in Multiple Myeloma; A Prospective Study in 199 Patients

High-dose chemotherapy with autologous stem cell support (ASCT) is the standard of care for eligible newly diagnosed Multiple Myeloma (MM) patients. Stem cell graft contamination by aberrant plasma cells (APCs) has been considered a possible predictive marker of subsequent clinical outcome, but the limited reports to date present unclear conclusions. We prospectively estimated the frequency of graft contamination using highly sensitive next-generation flow cytometry and evaluated its clinical impact in 199 myeloma patients who underwent an ASCT. Contamination (con+) was detected in 79/199 patients at a median level 2 × 10^-5. Its presence and levels were correlated with response to induction treatment, with 94%, 71% and 43% achieving CR, VGPR and PR, respectively. Importantly, con+ grafts conferred 2-fold and 2.8-fold higher patient-risk of not achieving or delaying reaching CR (4 vs. 11 months) and MRD negativity (5 vs. 18 months) post ASCT, respectively. Our data also provide evidence of a potentially skewed bone marrow (BM) reconstitution due to unpurged grafts, since con+ derived BM had significantly higher prevalence of memory B cells. These data, together with the absence of significant associations with baseline clinical features, highlight graft contamination as a potential biomarker with independent prognostic value for deeper responses, including MRD negativity. Longer follow-up will reveal if this corresponds to PFS or OS advantage.

Oncolytic virotherapy in hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) is a curative option for various hematologic malignancies. However, fatal complications, such as relapse and graft-versus-host disease (GVHD) hampered favorable HSCT outcomes. Cancer cells remained in the body following the conditioning regimen, or those contaminating the autologous graft can cause relapse. Although the relapse is much lesser in allogeneic HSCT, GVHD is still a life-threatening complication in this type of HSCT. Researchers are seeking various strategies to reduce relapse and GVHD in HSCT with minimum effects on the engraftment and immune-reconstitution. Oncolytic viruses (OVs) are emerging anti-cancer agents with promising results in battling solid tumors. OVs can selectively replicate in the malignant cells in which the antiviral immune responses have defected. Hence, they could be used as a purging agent to eradicate the tumoral contamination of autologous grafts with no damages to hematopoietic stem cells. Moreover, they have been shown to alleviate GVHD complications through modulating alloreactive T cell responses. Primary results promise using OVs as a strategy to reduce both relapse and GVHD in the HSCT without affecting hematologic and immunologic engraftment. Herein, we provide the latest findings in the field of OV therapy in HSCT and discuss their pros and cons.

Feasibility of six cycles of lenalidomide-based triplet induction before stem cell collection for newly diagnosed transplant-eligible multiple myeloma

OBJECTIVES

Achieving a deep response with induction therapy has a major impact on outcomes following autologous stem cell transplantation. Although longer and intensified induction therapy may provide better disease control, longer exposure to lenalidomide negatively affects stem cell yield. We examined the feasibility of 6 cycles of lenalidomide-based triplet induction therapy before stem cell collection in transplant-eligible multiple myeloma patients.

METHODS

In this prospective study, patients received a combination of bortezomib, lenalidomide, and dexamethasone for 6 cycles. For patients who did not achieve a deep response after 3 cycles, bortezomib was substituted with carfilzomib for the last 2 cycles (5th and 6th courses).

RESULTS

Although only half of the patients achieved a deep response after 3 cycles, all but 1 patient achieved a very good partial response (n = 4) or complete response (n = 5) after completing 6 cycles. Among 9 patients who received cyclophosphamide-based stem cell mobilization, 1 patient required a second mobilization that was successfully performed using plerixafor. After autologous transplantation, 7 patients showed complete response, including 5 with minimal residual disease-negative status.

CONCLUSION

This study demonstrates that 6 cycles of lenalidomide-based induction therapy before stem cell collection are a feasible and promising approach for transplant-eligible newly diagnosed multiple myeloma patients.The study is registered at UMIN Clinical Trials Registry as UMIN000026936.Trial registration: UMIN Japan identifier: UMIN000026936.

Autograft cellular composition and outcome in myeloma patients: Results of the prospective multicenter GOA study

BACKGROUND

Autologous stem cell transplantation (auto-SCT) is a widely used treatment option in multiple myeloma (MM) patients. The optimal graft cellular composition is not known.

STUDY DESIGN AND METHODS

Autograft cellular composition was analyzed after freezing by flow cytometry in 127 MM patients participating in a prospective multicenter study. The impact of graft cellular composition on hematologic recovery and outcome after auto-SCT was evaluated.

RESULTS

A higher graft CD34⁺ cell content predicted faster platelet recovery after auto-SCT in both the short and long term. In patients with standard-risk cytogenetics, a higher graft CD34⁺ count (>2.5 × 10⁶ /kg) was linked with shorter progression-free survival (PFS; 28 vs. 46 months, p = 0.04), but there was no difference in overall survival (OS) (p = 0.53). In a multivariate model, a higher graft CD34⁺ CD133⁺ CD38^- (>0.065 × 10⁶ /kg, p = 0.009) and NK cell count (>2.5 × 10⁶ /kg, p = 0.026), lenalidomide maintenance and standard-risk cytogenetics predicted better PFS. In contrast, a higher CD34⁺ count (>2.5 × 10⁶ /kg, p = 0.015) predicted worse PFS. A very low CD3⁺ cell count (≤20 × 10⁶ /kg, p = 0.001) in the infused graft and high-risk cytogenetics remained predictive of worse OS.

CONCLUSIONS

Autograft cellular composition may impact outcome in MM patients after auto-SCT. More studies are needed to define optimal graft composition.

Immunomodulators in newly diagnosed multiple myeloma: current and future concepts

Introduction: Impressive therapeutic progress is being made in the management of multiple myeloma (MM). his progress is related to the introduction of several new classes of therapeutic agents including proteasome inhibitors, immunomodulatory drugs (IMiDs) and monoclonal antibodies (MoAbs).Areas covered: In this manuscript, the role of the IMiDs thalidomide and lenalidomide in the management of newly diagnosed MM is discussed. The mode of action of IMiDs and their role in the management of newly diagnosed MM patients is highlighted. In addition, clinical data on how MoAbs such as the anti-CD38 antibody daratumumab can further increase the efficacy of IMiD-based first-line anti-myeloma regimens are provided. A database search in PubMed was carried out.Expert Opinion: Immunomodulation has become an indispensable part of successful anti-myeloma regimens both at relapse and at diagnosis. The combination of lenalidomide plus dexamethasone with an anti-CD38 MoAb such as daratumumab and a proteasome inhibitor such as bortezomib is currently one of the most potent first-line treatment regimens for MM. A better understanding on how IMiDs synergize with existing and new anti-myeloma treatments can further improve the outcome for patients. Optimal first-line therapy will continue to benefit the long-term outcome of a growing population of young and elderly MM patients.

Cost and efficacy of peripheral stem cell mobilization strategies in multiple myeloma

Mobilization of peripheral blood stem cells (PBSC) can be performed using plerixafor, which is expensive, or high-dose cyclophosphamide (HDCy). We hypothesized that the overall cost of mobilization with plerixafor might not be greater if the cost of complication management was considered. We performed a cost analysis of these two strategies. This multicentric observational study recruited patients with myeloma who underwent a first PBSC mobilization. We considered direct medical costs, including hospitalization, mobilization agents, apheresis, and supportive treatments. We included 111 patients, 54 and 57 in the HDCy and plerixafor groups, respectively. Cost of mobilization with HDCy was 5097 ± 2982€ vs. 10958 ± 1789€ for plerixafor (p < 0.0001). Cost of agents used was 1287 ± 779€ vs. 6552 ± 509€, respectively (p = 0.0009). The mean number of days of hospitalization was 2 and 2.1 days, respectively (p = 0.035). All patients achieved the minimum PBSC collection target (p = 1.0); however, ASCT was performed with HDCy in 67% patients and with plerixafor in 86% (p = 0.02). Plerixafor mobilization incurred a greater cost, mostly due to the greater cost of the drug. Hospitalization length in the two groups was similar in our series. Interestingly, plerixafor appeared to be a very effective and safe mobilizing approach translating into a greater ASCT success.

Stem Cell Mobilization and Autograft Minimal Residual Disease Negativity with Novel Induction Regimens in Multiple Myeloma

Autologous stem cell transplantation (ASCT) remains the standard of care for transplantation-eligible patients with multiple myeloma (MM). Bortezomib with lenalidomide and dexamethasone (VRD) is the most common triplet regimen for newly diagnosed MM in the United States. Carfilzomib with lenalidomide and dexamethasone (KRD) has shown promising efficacy and may supplant VRD. We compared stem cell yields and autograft minimal residual disease (MRD)-negativity after VRD and KRD induction. Deeper responses (ie, very good partial response or better) were more common with KRD. Precollection bone marrow (BM) cellularity, interval from the end of induction therapy to start of stem cell collection, and method of stem cell mobilization were similar for the 2 cohorts. Days to complete collection was greater with KRD (2.2 days, versus 1.81 days with VRD), which more often required ≥3 days of apheresis. Precollection viable CD34⁺ cell content was greater with VRD, as was collection yield (11.11 × 10⁶, versus 9.19 × 10⁶ with KRD). Collection failure (defined as <2 × 10⁶ CD34⁺ cells/kg) was more frequent with KRD (5.4% versus .7% with VRD). The difference in stem cell yield between VRD and KRD is associated with the degree of lenalidomide exposure. Age ≥70 years predicted poorer collection for both cohorts. Stem cell autograft purity/MRD-negativity was higher with KRD (81.4%, versus 57.1% with VRD). For both cohorts, MRD-negativity was attained in a larger fraction of autografts than in precollection BM. For patients proceeding to ASCT, the time to neutrophil/platelet engraftment was comparable in the 2 study arms. In summary, our data demonstrate that KRD induces deeper clinical responses and greater autograft purity than VRD without compromising stem cell yield or post-transplantation engraftment kinetics.

A Phase I Study of the Safety and Feasibility of Bortezomib in Combination With G-CSF for Stem Cell Mobilization in Patients With Multiple Myeloma

BACKGROUND

We previously reported that administration of bortezomib (BTZ) after 4 days of granulocyte colony-stimulating factor (G-CSF) significantly augments mobilization in mice. We hypothesized that administration of BTZ at peak G-CSF mobilization in patients with multiple myeloma (MM) would be safe, augment mobilization, and have an in vivo purging effect on circulating myeloma cells.

PATIENTS AND METHODS

This was a phase I study using 3 dose levels of BTZ. G-CSF was administered for 5 days. On the evening of the fourth day, a single dose of BTZ was administered. Peripheral blood was drawn 1 to 2 hours before and 15 to 18 hours after BTZ administration (before day 5 G-CSF administration) to analyze the mobilization effect of BTZ. Standard apheresis was then performed starting on day 5. After mobilization, patients underwent autologous stem cell transplantation (ASCT) per institutional guidelines.

RESULTS

Ten patients were enrolled. There were no dose-limiting toxicities. Median peripheral blood CD34⁺ cells at day 4 before BTZ administration was 16 per microliter and 15 hours later was 32 per microliter suggesting that administration of BTZ at peak G-CSF mobilization augments the mobilization effect of G-CSF. The effect of BTZ on circulating MM cells was unclear. All patients had successful engraftment after ASCT.

CONCLUSION

Administration of 1 dose of BTZ at peak G-CSF mobilization was safe and well tolerated, enhanced stem cell mobilization, and did not affect graft viability. The mobilization effect of BTZ at peak G-CSF mobilization shown in this phase I study needs to be confirmed in a larger randomized trial.

Bone marrow transplantation generates T cell-dependent control of myeloma in mice

Transplantation with autologous hematopoietic progenitors remains an important consolidation treatment for patients with multiple myeloma (MM) and is thought to prolong the disease plateau phase by providing intensive cytoreduction. However, transplantation induces inflammation in the context of profound lymphodepletion that may cause hitherto unexpected immunological effects. We developed preclinical models of bone marrow transplantation (BMT) for MM using Vk*MYC myeloma-bearing recipient mice and donor mice that were myeloma naive or myeloma experienced to simulate autologous transplantation. Surprisingly, we demonstrated broad induction of T cell-dependent myeloma control, most efficiently from memory T cells within myeloma-experienced grafts, but also through priming of naive T cells after BMT. CD8+ T cells from mice with controlled myeloma had a distinct T cell receptor (TCR) repertoire and higher clonotype overlap relative to myeloma-free BMT recipients. Furthermore, T cell-dependent myeloma control could be adoptively transferred to secondary recipients and was myeloma cell clone specific. Interestingly, donor-derived IL-17A acted directly on myeloma cells expressing the IL-17 receptor to induce a transcriptional landscape that promoted tumor growth and immune escape. Conversely, donor IFN-γ secretion and signaling were critical to protective immunity and were profoundly augmented by CD137 agonists. These data provide new insights into the mechanisms of action of transplantation in myeloma and provide rational approaches to improving clinical outcomes.

Influence of Clonal Plasma Cell Contamination of Peripheral Blood Stem Cell Autografts on Progression and Survival in Multiple Myeloma Patients After Autologous Peripheral Blood Stem Cell Transplantation in Long-term Observation

BACKGROUND

High-dose chemotherapy followed by autologous peripheral blood stem cell transplantation (auto-PBSCT) remains the mainstay of treatment of eligible patients diagnosed multiple myeloma. The role of clonal plasma cell (CPC) contamination was found as a reason for relapse, but results in terms of survival, progression, and purging were ambiguous. Therefore, the aim of the study was to explore the influence of CPC contamination in the autograft on survival and progression after auto-PBSCT.

STUDY DESIGN

The study included 59 patients diagnosed and treated for multiple myeloma in 1998-2004. Cells with coexpression of CD38⁺⁺⁺CD138⁺⁺CD56⁺ and lacking the expression of CD45, CD19, CD10, CD20, and CD23 were considered CPC in flow cytometry.

RESULTS

The risk of death and progression after auto-PBSCT increased significantly by 10% (P < .021) and 8% (P < .034) per 1 × 10⁶/kg of the CPC number, respectively. For CPC number above 2.96 × 10⁶/kg overall survival achieved clinical significance. Two years after auto-PBSCT, the risk of death was independent of CPC number among the patients who survived (P = .70). Analogous conclusions concerned results of progression-free survival at 1 year after auto-PBSCT.

CONCLUSIONS

High clonal plasma cell contamination (>2.96 ×1 0⁶/kg; 90th percentile of CPC number) is associated with the worst progression-free survival and overall survival. Therefore purging in vitro might be considered for the patients with the highest CPC contamination. Negative consequences of CPC contamination on the risk of death are observed for only 2 years after auto-PBSCT. Thereafter only those patients who had lower CPC contamination survived.

Prognostic value of sequencing-based minimal residual disease detection in patients with multiple myeloma who underwent autologous stem-cell transplantation

Background

Most patients with multiple myeloma (MM) are considered to be incurable, and relapse owing to minimal residual disease (MRD) is the main cause of death among these patients. Therefore, new technologies to assess deeper response are required.

Patients and methods

We retrospectively analyzed 125 patients with MM who underwent high-dose melphalan plus autologous stem-cell transplantation (ASCT) to detect MRD in autograft/bone marrow (BM) cells using a next-generation sequencing (NGS)-based method and allele-specific oligonucleotide-polymerase chain reaction (ASO-PCR).

Results

NGS-based method was applicable to 90% and this method had at least one to two logs greater sensitivity compared to ASO-PCR. MRD negative by NGS [MRD^NGS(−)] (defined as <10⁻⁶) in post-ASCT BM cases (n = 26) showed a significantly better progression-free survival (PFS) (96% at 4 years, P < 0.001) and overall survival (OS) (100% at 4 years, P =0.04) than MRD^NGS(+) in post-ASCT BM cases (n = 25). When restricting the analysis to the 39 complete response cases, patients who were MRD^NGS(−) (n = 24) showed a significantly better PFS than those that were MRD^NGS(+) (n = 15) (P =0.02). Moreover, MRD^NGS(−) in post-ASCT BM cases (n = 12) showed significantly a better PFS than MRD^NGS(+) cases (n = 7) where MRD was not detected by ASO-PCR (P = 0.001). Patients whose autografts were negative by NGS-based MRD assessment (<10⁻⁷) (n = 19) had 92% PFS and 100% OS at 4 years post-ASCT. Conversely, the NGS-based MRD positive patients who received post-ASCT treatment using novel agents (n = 49) had a significantly better PFS (P = 0.001) and tended to have a better OS (P= 0.214) than those that were untreated (n = 33).

Conclusions

Low level MRD detected by NGS-based platform but not ASO-PCR has significant prognostic value when assessing either the autograft product or BM cells post-ASCT.

Combination therapy with carfilzomib, lenalidomide and dexamethasone (KRd) results in an unprecedented purity of the stem cell graft in newly diagnosed patients with myeloma

Still, many physicians give 4 cycles of combination therapy to multiple myeloma patients prior to collection of stem cells for autologous bone marrow transplant. This tradition originates from older doxorubicin-containing regiments which limited the number of cycles due to cumulative cardiotoxicity. Using older regiments, most patients had residual myeloma cells in their autologous stem-cell grafts during collection. Emerging data show that newly diagnosed multiple myeloma patients treated with modern carfilzomib/lenalidomide/dexamethasone (KRd) therapy, on average, take 6 cycles until reaching minimal residual disease (MRD) negativity. We assessed newly diagnosed patients treated with KRd focusing MRD status both in the individual patient's bone marrow, and the corresponding autologous hematopoietic progenitor cell grafts during collection. Per protocol, stem-cell collection was allowed after 4 to 8 cycles of KRd. We found similar stem-cell yield independent of the number of cycles of KRd. At stem-cell collection, 11/30 patients (36.6%) were MRD negative in their bone marrow; all 11 patients had MRD negative hematopoietic progenitor cell grafts. Furthermore, 18/19 patients who were MRD positive in their bone marrows also had MRD negative hematopoietic progenitor cell grafts. These observations support 6 cycles of KRd as an efficacious and safe induction strategy prior to stem-cell collection.

Peripheral blood stem cell mobilization in multiple myeloma: Growth factors or chemotherapy?

High-dose therapy followed by autologous hematopoietic stem cell (HSC) transplant is considered standard of care for eligible patients with multiple myeloma. The optimal collection strategy should be effective in procuring sufficient HSC while maintaining a low toxicity profile. Currently available mobilization strategies include growth factors alone, growth factors in combination with chemotherapy, or growth factors in combination with chemokine receptor antagonists; however, the optimal strategy has yet to be elucidated. Herein, we review the risks and benefits of each approach.

Comparison of Minimal Residual Disease Detection by Multiparameter Flow Cytometry, ASO-qPCR, Droplet Digital PCR, and Deep Sequencing in Patients with Multiple Myeloma Who Underwent Autologous Stem Cell Transplantation

Multiple myeloma (MM) is a hematological malignancy with a poor prognosis, characterized by clonal proliferation of plasma cells in the bone marrow (BM). Relapse due to undetected minimal residual disease (MRD) is the leading cause of death among patients with MM. This review summarizes the methods and prognostic value of MRD assessment in BM and autografts from MM patients who underwent autologous stem cell transplantation (ASCT) by multiparameter flow cytometry (MFC), allele-specific oligonucleotide real-time quantitative PCR (ASO-qPCR), droplet digital PCR (ddPCR), and next-generation sequencing (NGS)-based detection methods. MRD assessment using NGS-based approaches has clear prognostic value and better sensitivity compared to traditional methods.

Cancer testis antigen MAGE C1 can be used to monitor levels of circulating malignant stem cells in the peripheral blood of multiple myeloma patients

PURPOSE

Monitoring the levels of malignant disease-causing cells in multiple myeloma, as opposed to the clinical symptoms alone, is an important move forward in the management of this disease. While current methods including multiparametric flow cytometry and PCR analysis of the clonal plasma cells can be used in a patient-specific manner, their use is limited and the fundamental malignant progenitor cell is not being monitored. The expression of cancer testis antigen MAGE C1 has been linked to the malignant stem cell in this disease, and thus, we investigated the use of both flow cytometric and qRTPCR approaches to monitor its expression as an alternative monitoring methodology in this pilot study.

METHODS

We compared the levels of MAGE C1 in the peripheral blood to serum M protein and serum beta 2 microglobulin levels at 3-monthly intervals over a 2-year period, for 12 patients on chemotherapy regimens and 4 patients undergoing stem cell transplantation.

RESULTS AND CONCLUSIONS

The analysis indicated that the novel flow cytometric analysis of MAGE C1 expression in the peripheral blood was extremely relevant as a potential minimal residual disease-monitoring tool. Expression of this cancer testis antigen was detectable in all patients throughout treatment, with comparable increases and decreases to serum M protein and/or serum beta 2 microglobulin, but with the advantage of being able to detect disease at a more sensitive level. Furthermore, due to the increased sensitivity, the ability to pre-empt disease relapse before clinical changes were evident, was preliminarily indicated. The qRTPCR approach showed potential as a monitoring tool in the chemotherapy patient cohort, with the mRNA MAGE C1 levels following a similar pattern of expression observed in the flow cytometry analysis.

Immunoselection techniques in hematopoietic stem cell transplantation

Hematopoietic Stem Cells Transplantation (HSCT) is an effective treatment for hematological and non-hematological diseases. The main challenge in autologous HSCT is purging of malignant cells to prevent relapse. In allogeneic HSCT graft-versus-host disease (GvHD) and opportunistic infections are frequent complications. Two types of graft manipulation have been introduced: the first one in the autologous context aimed at separating malignant cells from hematopoietic stem cells (HSC), and the second one in allogeneic HSCT aimed at reducing the incidence of GvHD and at accelerating immune reconstitution. Here we describe the manipulations used for cell purging in autologous HSCT or for T Cell Depletion (TCD) and T cell selection in allogeneic HSCT. More complex manipulations, requiring a Good Manufacturing Practice (GMP) facility, are briefly mentioned.

The use of MAGE C1 and flow cytometry to determine the malignant cell type in multiple myeloma

The malignant cell phenotype of Multiple Myeloma (MM) remains unclear with studies proposing it to be either clonotypic B or proliferating plasma cells. Cancer/testis antigen MAGE C1 is being extensively studied in MM and it has been suggested that it is involved in the pathogenesis of the cancer. Therefore, we report on the use of MAGE C1 to determine the malignant cell phenotype in MM using flow cytometry. Bone marrow aspirate (BM) and peripheral blood (PB) was collected from twelve MM patients at diagnosis, as well as three MM disease-free controls. Mononuclear cells were isolated using density-gradient centrifugation, and stabilized in 80% ethanol, before analysis via flow cytometry using relevant antibodies against B cell development cell-surface markers and nuclear MAGE C1. MAGE C1 expression was observed consistently in the early stem cells (CD34+) and early pro-B to pre-B cells (CD34+/-/CD19+), as well as the proliferating plasma cells in both the MM PB and BM, while no expression was observed in the corresponding control samples. Monoclonality indicated a common origin of these cell types suggesting that the CD34+/MAGE C1+ are the primary malignant cell phenotype that sustains the downstream B cell maturation processes. Furthermore, this malignant cell phenotype was not restricted to the BM but also found in the circulating PB cells.

Content of endothelial progenitor cells in autologous stem cell grafts predict survival after transplantation for multiple myeloma

Multiple myeloma (MM) is considered an incurable B cell malignancy, although many patients can benefit from high-dose therapy with autologous stem cell transplantation (ASCT) as a first-line treatment. In non-Hodgkin lymphoma (NHL), ASCT is usually performed after relapse with curative intent. Disease progression is often associated with increased angiogenesis, in which endothelial progenitor cells (EPC) may have a central role. Here, we investigated the clinical impact of EPC levels in peripheral blood stem cell (PBSC) autografts for MM and NHL patients who received ASCT. EPC were identified by flow cytometry as aldehyde dehydrogenase(hi) CD34(+) vascular endothelial growth factor receptor 2(+) CD133(+) cells in both MM and NHL autografts. In MM, there was a positive correlation between EPC percentage and serum (s)-β2-microglobulin levels (r(2) = .371, P = .002). Unlike for NHL patients, MM patients with high numbers of infused EPC (EPC cells per kilogram) during ASCT had significant shorter progression-free survival (PFS) (P = .035), overall survival (P = .044) and time to next treatment (P = .009). In multivariate analysis, EPC cells per kilogram was a significant independent negative prognostic indicator of PFS (P = .03). In conclusion, the presence of high number of EPC in PBSC grafts is associated with adverse prognosis after ASCT in MM.

The ex vivo purge of cancer cells using oncolytic viruses: recent advances and clinical implications

Hematological malignancies are treated with intensive high-dose chemotherapy, with or without radiation. This is followed by hematopoietic stem cell (HSC) transplantation (HSCT) to rescue or reconstitute hematopoiesis damaged by the anticancer therapy. Autologous HSC grafts may contain cancer cells and purging could further improve treatment outcomes. Similarly, allogeneic HSCT may be improved by selectively purging alloreactive effector cells from the graft rather than wholesale immune cell depletion. Viral agents that selectively replicate in specific cell populations are being studied in experimental models of cancer and immunological diseases and have potential applications in the context of HSC graft engineering. This review describes preclinical studies involving oncolytic virus strains of adenovirus, herpes simplex virus type 1, myxoma virus, and reovirus as ex vivo purging agents for HSC grafts, as well as in vitro and in vivo experimental studies using oncolytic coxsackievirus, measles virus, parvovirus, vaccinia virus, and vesicular stomatitis virus to eradicate hematopoietic malignancies. Alternative ex vivo oncolytic virus strategies are also outlined that aim to reduce the risk of relapse following autologous HSCT and mitigate morbidity and mortality due to graft-versus-host disease in allogeneic HSCT.

Reprint of: Back to the future! The evolving role of maintenance therapy after hematopoietic stem cell transplantation

Relapse is a devastating event for patients with hematologic cancers treated with hematopoietic stem cell transplantation. In most situations, relapse treatment options are limited. Maintenance therapy offers the possibility of delaying or avoiding disease recurrence, but its role remains unclear in most conditions that we treat with transplantation. Here, Dr. Hourigan presents an overview of minimal residual disease (MRD) measurement in hematologic malignancies and the applicability of MRD-based post-transplantation interventions. Dr. McCarthy reviews current knowledge of maintenance therapy in the autologous transplantation context, with emphasis on immunologic interventions and immune modulation strategies designed to prevent relapse. Dr. de Lima discusses current lines of investigation in disease recurrence prevention after allogeneic transplantation, focusing on acute myeloid leukemia and myelodysplastic syndrome.

The prognostic impact of peripheral blood progenitor cell dose following high-dose therapy and autologous stem cell transplant for hematologic malignancies

High-dose chemotherapy (HDT) followed by autologous peripheral blood progenitor cell transplant (PBPCT) has become a standard intervention in certain clinical settings of hematologic malignancies, particularly multiple myeloma and relapsed/refractory lymphoma. While the minimal required PBPCs infused, as defined by number of CD34 + cells, has been relatively well delineated for adequate hematopoietic recovery post-HDT, optimal PBPC dose has not been clearly defined. This is particularly relevant in the context of retrospective data suggesting improved survival outcomes with increased PBPC doses. The potential confounding of these data as they relate to disease risk is discussed within this review. Additionally, other retrospective data have suggested that enhanced quantitative lymphocyte subset reconstitution post-HDT-PBPCT may confer progression-free and overall survival advantage. These reported series herein reviewed may inform discussion of future, prospective clinical trials with the intent of defining optimal autologous PBPC dose following HDT, especially as it may relate to metrics beyond hematopoietic recovery.

Bone marrow plasma cell assessment before peripheral blood stem cell mobilization in patients with multiple myeloma undergoing autologous stem cell transplantation

The current definition of complete response (CR) in multiple myeloma (MM) includes negative serum and urine immunofixation (IFE) tests and <5% bone marrow plasma cells (BMPCs). However, many studies of the prognostic impact of pretransplant response have not included BMPCs. We evaluated the prognostic impact of BMPC assessment before peripheral blood stem cell (PBSC) mobilization on subsequent transplant outcomes. BMPCs were assessed by CD138, kappa, and lambda immunostaining in 106 patients. After a median followup of 24.5 months, patients with <5% BMPCs had a significantly better progression-free survival (PFS) compared to those with ≥5% BMPCs (P = 0.005). Patients with <5% BMPCs + serologic CR showed superior PFS compared to those with <5% BMPCs + serologic non-CR (P = 0.050) or ≥5% BMPCs + serologic non-CR (P = 0.001). Interestingly, the prognostic impact of BMPCs was more apparent for patients who did not achieve a serologic CR (P = 0.042) compared to those with a serologic CR (P = 0.647). We concluded that IFE negativity and <5% BMPCs before PBSC mobilization were important factors to predict PFS in patients with MM undergoing ASCT. Particularly, a significant impact of <5% BMPCs was observed in patients who did not achieve IFE negativity.

Autologous haematopoietic stem cell mobilisation in multiple myeloma and lymphoma patients: a position statement from the European Group for Blood and Marrow Transplantation

Autologous haematopoietic SCT with PBSCs is regularly used to restore BM function in patients with multiple myeloma or lymphoma after myeloablative chemotherapy. Twenty-eight experts from the European Group for Blood and Marrow Transplantation developed a position statement on the best approaches to mobilising PBSCs and on possibilities of optimising graft yields in patients who mobilise poorly. Choosing the appropriate mobilisation regimen, based on patients' disease stage and condition, and optimising the apheresis protocol can improve mobilisation outcomes. Several factors may influence mobilisation outcomes, including older age, a more advanced disease stage, the type of prior chemotherapy (e.g., fludarabine or melphalan), prior irradiation or a higher number of prior treatment lines. The most robust predictive factor for poor PBSC collection is the CD34(+) cell count in PB before apheresis. Determination of the CD34(+) cell count in PB before apheresis helps to identify patients at risk of poor PBSC collection and allows pre-emptive intervention to rescue mobilisation in these patients. Such a proactive approach might help to overcome deficiencies in stem cell mobilisation and offers a rationale for the use of novel mobilisation agents.

Role of allogeneic stem cell transplantation in multiple myeloma

Multiple myeloma is currently incurable using standard treatment regimens. While the introduction of high-dose chemotherapy with autologous stem cell rescue has been shown to increase overall survival when compared with chemotherapy alone, this strategy is palliative. Allogeneic stem cell transplantation provides the potential for long-term disease-free survival in a small proportion of patients, although its application has been limited by procedure-related mortality, reflecting the intensive myeloablative conditioning given. Recently, reduced intensity conditioning regimens have been developed in an attempt to reduce toxicity whilst preserving the allogeneic graft-versus-myeloma effect, therefore maintaining the potential for disease eradication. This review aims to examine the current position of allogeneic transplantation in the management of myeloma.

Back to the future! The evolving role of maintenance therapy after hematopoietic stem cell transplantation

Relapse is a devastating event for patients with hematologic cancers treated with hematopoietic stem cell transplantation. In most situations, relapse treatment options are limited. Maintenance therapy offers the possibility of delaying or avoiding disease recurrence, but its role remains unclear in most conditions that we treat with transplantation. Here, Dr. Hourigan presents an overview of minimal residual disease (MRD) measurement in hematologic malignancies and the applicability of MRD-based post-transplantation interventions. Dr. McCarthy reviews current knowledge of maintenance therapy in the autologous transplantation context, with emphasis on immunologic interventions and immune modulation strategies designed to prevent relapse. Dr. de Lima discusses current lines of investigation in disease recurrence prevention after allogeneic transplantation, focusing on acute myeloid leukemia and myelodysplastic syndrome.

Plasmonic nanobubbles as tunable cellular probes for cancer theranostics

This review is focused on a novel cellular probe, the plasmonic nanobubble (PNB), which has the dynamically tunable and multiple functions of imaging, diagnosis, delivery, therapy and, ultimately, theranostics. The concept of theranostics was recently introduced in order to unite the clinically important stages of treatment, namely diagnosis, therapy and therapy guidance, into one single, rapid and highly accurate procedure. Cell level theranostics will have far-reaching implications for the treatment of cancer and other diseases at their earliest stages. PNBs were developed to support cell level theranostics as a new generation of on-demand tunable cellular probes. A PNB is a transient vapor nanobubble that is generated within nanoseconds around an overheated plasmonic nanoparticle with a short laser pulse. In the short term, we expect that PNB technology will be rapidly adaptable to clinical medicine, where the single cell resolution it provides will be critical for diagnosing incipient or residual disease and eliminating cancer cells, while leaving healthy cells intact. This review discusses mechanisms of plasmonic nanobubbles and their biomedical applications with the focus on cancer cell theranostics.

Reovirus as a successful ex vivo purging modality for multiple myeloma

Autologous stem cell rescue (ASCT) following high-dose myeloablative chemotherapy is considered to be a therapeutic option for many multiple myeloma (MM) patients; however relapse post ASCT presents a major challenge. The oncolytic potential of reovirus has been previously demonstrated and is currently undergoing phase I monotherapy clinical trials for MM and phase II/III clinical trials for solid tumors. Here we tested the hypothesis that reovirus can successfully purge MM in a murine model that partially recapitulates human MM. RPMI 8226, MM1S, H929 and U266 human myeloma cell lines were exposed to reovirus and oncolysis was assessed. Apheresis product admixed with MM cells was purged with live reovirus (LV) or dead virus (DV) and purging efficacy was monitored via flow cytometry, reverse transcribed-PCR (RT-PCR) and disease relapse in non obese diabetic/severe combined immune deficient (NOD/SCID) mice. Significant LV purging was seen with MM1S, H929 and U266 and the complete ex vivo purging achieved with RPMI 8226 was confirmed by flow cytometry, RT-PCR and absence of disease relapse in vivo. Mice that received LV-purged autografts exhibited 100% survival in comparison to mice that received DV-purged controls. Reovirus's unique ability to kill MM while sparing hematopoietic stem cells places it as an attractive purging agent for MM during ASCT.

Peripheral blood stem cell mobilization in multiple myeloma patients treat in the novel therapy-era with plerixafor and G-CSF has superior efficacy but significantly higher costs compared to mobilization with low-dose cyclophosphamide and G-CSF

Studies comparing the efficacy and cost of peripheral blood stem and progenitor cells mobilization with low-dose cyclophosphamide (LD-CY) and granulocyte-colony stimulating factor (G-CSF) against plerixafor and G-CSF, in multiple myeloma (MM) patients treated in the novel therapy-era are not available. Herein, we report mobilization outcomes of 107 patients who underwent transplantation within 1-year of starting induction chemotherapy with novel agents. Patients undergoing mobilization with LD-CY (1.5 gm/m(2)) and G-CSF (n = 74) were compared against patients receiving plerixafor and G-CSF (n = 33). Compared to plerixafor, LD-CY was associated with a significantly lower median peak peripheral blood CD34+ cell count (68/µL vs. 36/µL, P = 0.048), and lower CD34+ cell yield on day 1 of collection (6.9 × 10(6)/kg vs. 2.4 × 10(6)/kg, P = 0.001). Six patients (8.1%) in the LD-CY group experienced mobilization failure, compared to none in the plerixafor group. The total CD34+ cell yield was significantly higher in the plerixafor group (median 11.6 × 10(6)/kg vs. 7 × 10(6)/kg; P-value = 0.001). Mobilization with LD-CY was associated with increased (albeit statistically non-significant) episodes of febrile neutropenia (5.4% vs. 0%; P = 0.24), higher use of intravenous antibiotics (6.7% vs. 3%; P = 0.45), and need for hospitalizations (9.4% vs. 3%; P = 0.24). The average total cost of mobilization in the plerixafor group was significantly higher compared to the LD-CY group ($28,980 vs. $19,626.5 P-value < 0.0001). In conclusion, in MM plerixafor-based mobilization has superior efficacy, but significantly higher mobilization costs compared to LD-CY mobilization. Our data caution against the use of LD-CY in MM patients for mobilization, especially after induction with lenalidomide-containing regimens.

Detection of minimal residual disease in patients with multiple myeloma using clonotype-specific PCR primers designed from DNA extracted from archival bone marrow slides

Polymerase chain reaction (PCR)-negative molecular complete remission (mCR) can be induced by stem cell transplantation in some patients with multiple myeloma (MM) and is associated with long-term progression-free survival (PFS). The detection of molecular minimal residual disease (MRD), however, requires fresh or frozen materials for designing clone-specific primers, which are not always readily available. In this study, we used DNA extracted from archival bone marrow (BM) slides for PCR to detect MRD in 50 patients with MM who received various induction therapies and autologous peripheral blood stem cell transplantation (ASCT). Clonotype-specific immunoglobulin (Ig) H PCR primers were prepared for 32 of 50 cases (64%) using BM slides, and for 9 of 14 cases (64%) using fresh BM cells. DNA in peripheral blood stem cell autografts of the 22 patients who achieved at least a partial response after ASCT was subjected to PCR to amplify clonotype-specific rearranged IgH gene sequences. The median PFS of the eight patients with MRD-positive autografts was 18 months, whereas that of 14 patients with MRD-negative autografts was not reached at a median follow-up of 27 months (p = 0.012). Post-ASCT PFS of the four patients who achieved mCR was 100% at a median follow-up of 47 months. These results indicate that archival BM slides can serve as a source of DNA for preparing clonotype-specific primers for MRD monitoring in patients with MM whose cryopreserved myeloma cells are not available for DNA preparation. Our results also suggest that patients with MM who received MRD-negative autografts and achieved mCR have a long PFS.

Selective purging of human multiple myeloma cells from autologous stem cell transplantation grafts using oncolytic myxoma virus

Autologous stem cell transplantation and novel therapies have improved overall survival of patients with multiple myeloma; however, most patients relapse and eventually succumb to their disease. Evidence indicates that residual cancer cells contaminate autologous grafts and may contribute to early relapses after autologous stem cell transplantation. Here, we demonstrate that ex vivo treatment with an oncolytic poxvirus called myxoma virus results in specific elimination of human myeloma cells by inducing rapid cellular apoptosis while fully sparing normal hematopoietic stem and progenitor cells. The specificity of this elimination is based on strong binding of the virus to myeloma cells coupled with an inability of the virus to bind or infect CD34(+) hematopoietic stem and progenitor cells. These 2 features allow myxoma to readily identify and distinguish even low levels of myeloma cells in complex mixtures. This ex vivo rabbit-specific oncolytic poxvirus called myxoma virus treatment also effectively inhibits systemic in vivo engraftment of human myeloma cells into immunodeficient mice and results in efficient elimination of primary CD138(+) myeloma cells contaminating patient hematopoietic cell products. We conclude that ex vivo myxoma treatment represents a safe and effective method to selectively eliminate myeloma cells from hematopoietic autografts before reinfusion.

Advances in the autologous and allogeneic transplantation strategies for multiple myeloma

BACKGROUND

Multiple myeloma is largely an incurable malignant plasma cell neoplasm; however, the landscape of its treatment is rapidly changing.

METHODS

The recent literature on both autologous and allogeneic transplant approaches for multiple myeloma was reviewed.

RESULTS

High-dose chemotherapy followed by autologous hematopoietic cell transplantation (HCT) remains an integral component of upfront treatment strategy, and the incorporation of novel immunomodulators and proteasome inhibitor to induction regimens improves response rates and increases overall survivals. Bortezomib and lenalidomide-based combination chemotherapy regimens have become the standard induction myeloma therapy. When myeloma patients proceed to transplant after novel combination regimens, their response rates are further improved. Despite these recent major improvements, myeloma remains incurable and long-term survival appears elusive. Due in part to a potential graft-vs-myeloma effect, allogeneic HCT is a potentially curative transplant option. However, initial attempts have been hampered by the high transplant-related mortality. With a reduction of toxicity, allogeneic transplant approaches with reduced-intensity conditioning have been utilized, although they are subject to continued disease progression and relapse following transplantation. Recent research efforts have shifted to the use of a tandem autologous-allogeneic HCT approach. The long-term follow-up of this new strategy is awaited.

CONCLUSIONS

Recent advances in HCT have improved outcomes of patients with multiple myeloma. Ongoing research activity focuses on the strategies to improve outcomes of HCT by incorporation of tandem autologous-allogeneic transplantation schema, novel conditioning regimens, and the use of consolidation and maintenance therapy.

Ex vivo graft purging and expansion of autologous blood progenitor cell products from patients with multiple myeloma

Autologous peripheral blood progenitor cell (PBPC) transplantation is the treatment of choice for selected myeloma patients. However, tumor cells contaminating the apheresis product are a potential source of relapse. Here we report a sequential purging strategy targeting mature and immature clonogenic myeloma cell populations in the autograft. Thawed PBPC products of myeloma patients were treated with rituximab to kill CD138(-)20(+) B cells (highly clonogenic immature cells), and bortezomib to target CD138(+) cells (normal and differentiated myeloma plasma cells), followed by coculture with allogeneic mesenchymal stem cells (MSC) from normal donors. After 7 days of coculture, nonadherent cells were removed and cultured in the absence of MSC for an additional 7 days. Then, efficacy of purging (removal of CD138(-)20(+) and CD138(+) cells) was assessed by flow cytometry and PCR. We used our ex vivo purging strategy to treat frozen aphereses from 16 patients. CD138(+) and CD138(-)20(+)(19(+)) cells present in the initial products were depleted more than 3 and 4 logs, respectively based on 10(6) flow-acquisition events, and to levels below the limit of detection by PCR. In contrast, total nucleated cell (TNC), CD34(+) cell, and colony-forming cell numbers were increased by approximately 12 to 20, 8-, and 23-fold, respectively. Overall, ex vivo treatment of apheresis products with rituximab, bortezomib, and coculture with normal donor MSC depleted mature and immature myeloma cells from clinical aphereses while expanding the normal hematopoietic progenitor cell compartment.

High-dose therapy and autologous peripheral blood stem cell transplantation in patients with multiple myeloma

Since its introduction in 1983, high-dose therapy followed by autologous peripheral blood stem cell transplantation is a pillar of the treatment of patients with multiple myeloma. In the last decades, a multitude of clinical trials helped to improve strategies based on high-dose therapy and autologous stem cell transplantation resulting in a continuously prolongation of overall survival of patients. In this chapter we will review the progress, which has been made in order to enhance the mobilisation of autologous stem cells and increase the effectiveness of this treatment.

Autograft mediated adoptive immunotherapy of cancer in the context of autologous stem cell transplantation

The infused stem cell autograft in autologous stem cell transplantation (ASCT) has been viewed mainly as hematologic rescue from the myelosuppressive side effect of conditioning regimens. However, recent reports have shown that the immune effector cells collected at the same time as the stem cells can produce an autologous graft-versus-tumor effect, similar to the graft-versus-tumor effect seen in allogeneic stem cell transplantation without the detrimental effects of graft-versus-host disease. In this article, we review the different immune effector cells collected and infused from the stem cell autograft and their association with clinical outcome post-ASCT, suggesting that ASCT can be viewed not only as a therapeutic maneuver to recover bone marrow function after deliver high-dose chemotherapy, but also as an adoptive immunotherapeutic intervention capable of eradicating residual tumor cells in patients with cancer.

International Myeloma Working Group Consensus Statement Regarding the Current Status of Allogeneic Stem-Cell Transplantation for Multiple Myeloma

Purpose

To define consensus statement regarding allogeneic stem-cell transplantation (Allo-SCT) as a treatment option for multiple myeloma (MM) on behalf of International Myeloma Working Group.

Patients and Methods

In this review, results from prospective and retrospective studies of Allo-SCT in MM are summarized.

Results

Although the introduction of reduced-intensity conditioning (RIC) has lowered the high treatment-related mortality associated with myeloablative conditioning, convincing evidence is lacking that Allo-RIC improves the survival compared with autologous stem-cell transplantation.

Conclusion

New strategies are necessary to make Allo-SCT safer and more effective for patients with MM. Until this is achieved, Allo-RIC in myeloma should only be recommended in the context of clinical trials.

Oncolytic viral purging of leukemic hematopoietic stem and progenitor cells with Myxoma virus

High-dose chemotherapy and radiation followed by autologous blood and marrow transplantation (ABMT) has been used for the treatment of certain cancers that are refractory to standard therapeutic regimes. However, a major challenge with ABMT for patients with hematologic malignancies is disease relapse, mainly due to either contamination with cancerous hematopoietic stem and progenitor cells (HSPCs) within the autograft or the persistence of residual therapy-resistant disease niches within the patient. Oncolytic viruses represent a promising therapeutic approach to prevent cancer relapse by eliminating tumor-initiating cells that contaminate the autograft. Here we summarize an ex vivo "purging" strategy with oncolytic Myxoma virus (MYXV) to remove cancer-initiating cells from patient autografts prior to transplantation. MYXV, a novel oncolytic poxvirus with potent anti-cancer properties in a variety of in vivo tumor models, can specifically eliminate cancerous stem and progenitor cells from samples obtained from acute myelogenous leukemia (AML) patients, while sparing normal CD34+ hematopoietic stem and progenitor cells capable of rescuing hematopoiesis following high dose conditioning. We propose that a broader subset of patients with intractable hematologic malignancies who have failed standard therapy could become eligible for ABMT when the treatment schema is coupled with ex vivo oncolytic therapy.

Treatment of multiple myeloma: a comprehensive review

Multiple myeloma (MM) is a neoplastic plasma cell disorder that results in end-organ damage (hypercalcemia, renal insufficiency, anemia, or skeletal lesions). Patients should not be treated unless they have symptomatic (end-organ damage) MM. They should be classified as having high-risk or standard-risk disease. Patients are classified as high risk in the presence of hypodiploidy or deletion of chromosome 13 (del[13]) with conventional cytogenetics, the presence of t(4:14), t(14;16), t(14;20) translocations or del(17p) with fluorescence in situ hybridization. High-risk disease accounts for about 25% of patients with symptomatic MM. If the patient is deemed eligible for an autologous stem cell transplantation (ASCT), 3 or 4 cycles of lenalidomide and low-dose dexamethasone, or bortezomib and dexamethasone, or thalidomide and dexamethasone are reasonable choices. Stem cells should then be collected and one may proceed with an ASCT. If the patient has a complete response or a very good partial response (VGPR), the patient may be followed without maintenance therapy. If the patient has a less than VGPR, a second ASCT is encouraged. If the patient is in the high-risk group, a bortezomib-containing regimen to maximum response followed by 2 additional cycles of therapy is a reasonable approach. Lenalidomide and low-dose dexamethasone is another option for maintenance until progression. If the patient is considered ineligible for an ASCT, then melphalan, prednisone, and thalidomide is suggested for the standard-risk patient, and melphalan, prednisone, and bortezomib (MPV) for the high-risk patient. Treatment of relapsed or refractory MM is covered. The novel therapies-thalidomide, bortezomib, and lenalidomide-have resulted in improved survival rates. The complications of MM are also described. Multiple myeloma is a plasma cell neoplasm that is characterized by a single clone of plasma cells producing a monoclonal protein (M-protein). The malignant proliferation of plasma cells produces skeletal destruction that leads to bone pain and pathologic fractures. The M-protein might lead to renal failure, hyperviscosity syndrome, or through the suppression of uninvolved immunoglobulins, recurrent infections. Anemia and hypercalcemia are common complications.