International Myeloma Working Group molecular classification of multiple myeloma: spotlight review

Myeloma is a malignant proliferation of monoclonal plasma cells. Although morphologically similar, several subtypes of the disease have been identified at the genetic and molecular level. These genetic subtypes are associated with unique clinicopathological features and dissimilar outcome. At the top hierarchical level, myeloma can be divided into hyperdiploid and non-hyperdiploid subtypes. The latter is mainly composed of cases harboring IgH translocations, generally associated with more aggressive clinical features and shorter survival. The three main IgH translocations in myeloma are the t(11;14)(q13;q32), t(4;14)(p16;q32) and t(14;16)(q32;q23). Trisomies and a more indolent form of the disease characterize hyperdiploid myeloma. A number of genetic progression factors have been identified including deletions of chromosomes 13 and 17 and abnormalities of chromosome 1 (1p deletion and 1q amplification). Other key drivers of cell survival and proliferation have also been identified such as nuclear factor- B-activating mutations and other deregulation factors for the cyclin-dependent pathways regulators. Further understanding of the biological subtypes of the disease has come from the application of novel techniques such as gene expression profiling and array-based comparative genomic hybridization. The combination of data arising from these studies and that previously elucidated through other mechanisms allows for most myeloma cases to be classified under one of several genetic subtypes. This paper proposes a framework for the classification of myeloma subtypes and provides recommendations for genetic testing. This group proposes that genetic testing needs to be incorporated into daily clinical practice and also as an essential component of all ongoing and future clinical trials.

The molecular characterization and clinical management of multiple myeloma in the post-genome era

Cancer-causing mutations disrupt coordinated, precise programs of gene expression that govern cell growth and differentiation. Microarray-based gene-expression profiling (GEP) is a powerful tool to globally analyze these changes to study cancer biology and clinical behavior. Despite overwhelming genomic chaos in multiple myeloma (MM), expression patterns within tumor samples are remarkably stable and reproducible. Unique expression patterns associated with recurrent chromosomal translocations and ploidy changes defined molecular classes with differing clinical features and outcomes. Combined molecular techniques also dissected two distinct, reproducible forms of hyperdiploid disease and have molecularly defined MM with high risk for poor clinical outcome. GEP is now used to risk-stratify patients with newly diagnosed MM. Groups with high-risk features are evident in all GEP-defined MM classes, and GEP studies of serial samples showed that risk increases over time, with relapsed disease showing dramatic GEP shifts toward a signature of poor outcomes. This suggests a common mechanism of disease evolution and potentially reflects preferential expansion of therapy-resistant cells. Correlating GEP-defined disease class and risk with outcomes of therapeutic regimens reveals class-specific benefits for individual agents, as well as mechanistic insights into drug sensitivity and resistance. Here, we review modern genomics contributions to understanding MM pathogenesis, prognosis, and therapy.

Genetic polymorphisms of EPHX1, Gsk3beta, TNFSF8 and myeloma cell DKK-1 expression linked to bone disease in myeloma

Bone disease in myeloma occurs as a result of complex interactions between myeloma cells and the bone marrow microenvironment. A custom-built DNA single nucleotide polymorphism (SNP) chip containing 3404 SNPs was used to test genomic DNA from myeloma patients classified by the extent of bone disease. Correlations identified with a Total Therapy 2 (TT2) (Arkansas) data set were validated with Eastern Cooperative Oncology Group (ECOG) and Southwest Oncology Group (SWOG) data sets. Univariate correlates with bone disease included: EPHX1, IGF1R, IL-4 and Gsk3beta. SNP signatures were linked to the number of bone lesions, log(2) DKK-1 myeloma cell expression levels and patient survival. Using stepwise multivariate regression analysis, the following SNPs: EPHX1 (P=0.0026); log(2) DKK-1 expression (P=0.0046); serum lactic dehydrogenase (LDH) (P=0.0074); Gsk3beta (P=0.02) and TNFSF8 (P=0.04) were linked to bone disease. This assessment of genetic polymorphisms identifies SNPs with both potential biological relevance and utility in prognostic models of myeloma bone disease.

Serial measurement of serum C-reactive protein levels can identify patients at risk for severe complications following autologous stem cell transplantation

The value of serum C-reactive protein (CRP) levels as a predictor of complications in neutropenic patients needs to be further defined. We sought to identify an association between severe complications and daily CRP levels measured in 104 multiple myeloma patients during the 3 week period following high-dose melphalan and autologous transplant. Significantly higher mean CRP levels and CRP velocity of increase were observed among patients with severe complications. A cut-off point of 100 mg/l (CRP levels) and 15 mg/l/day (CRP velocity) identified patients likely to suffer severe complications with 86 and 75% sensitivity, respectively. Prospective validation of this model is currently underway.

International myeloma working group (IMWG) consensus statement and guidelines regarding the current status of stem cell collection and high-dose therapy for multiple myeloma and the role of plerixafor (AMD 3100)

Multiple myeloma is the most common indication for high-dose chemotherapy with autologous stem cell support (ASCT) in North America today. Stem cell procurement for ASCT has most commonly been performed with stem cell mobilization using colony-stimulating factors with or without prior chemotherapy. The target CD34+ cell dose to be collected as well as the number of apheresis performed varies throughout the country, but a minimum of 2 million CD34+ cells/kg has been traditionally used for the support of one cycle of high-dose therapy. With the advent of plerixafor (AMD3100) (a novel stem cell mobilization agent), it is pertinent to review the current status of stem cell mobilization for myeloma as well as the role of autologous stem cell transplantation in this disease. On June 1, 2008, a panel of experts was convened by the International Myeloma Foundation to address issues regarding stem cell mobilization and autologous transplantation in myeloma in the context of new therapies. The panel was asked to discuss a variety of issues regarding stem cell collection and transplantation in myeloma especially with the arrival of plerixafor. Herein, is a summary of their deliberations and conclusions.

MDS-associated cytogenetic abnormalities (MDS-CA) after total therapy (TT) regimens for newly diagnosed multiple myeloma (MM): Apparent surge after introduction of post-transplant consolidation chemotherapy (CONS) in TT2 and TT3

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Background: We have previously reported on the variables associated with the development of MDS-CA in the context of autologous transplant-supported high-dose therapy regimens for MM (Barlogie et al, Blood 2008). Methods: Due to a perceived increase in MDS-CA frequency, our MM data base was reviewed again to determine the potential effect of CONS introduced in TT2 and retained in TT3 trials. The frequency of MDS-CA post-transplant was determined, using Kaplan-Meier estimate plots, for 183 patients who received TT1, 554 enrolled in TT2 and 305 receiving TT3. Persistence of MDS-CA implied their documentation on 3 successive occasions. Results: 3-year MDS-CA estimates were 2% for both TT1 and TT2 and 4% for TT3 (TT3 v TT2, p=0.04; TT3 v TT1, p=0.11); persistent MDS-CA were also more frequently observed in TT3 in comparison with TT2 and TT1 (2% v 0% v 0%, both p=0.01). Multivariate analysis of features associated with transient and persistent MDS-CA revealed TT3 as an adverse feature (HR=2.84, p=0.043), along with incomplete platelet recovery of <165,000/uL 3mo after 1st transplant. Conclusions: Despite reduced induction chemotherapy prior to and CONS after tandem melphalan (200mg/m2)-based autotransplants from 4 in TT2 to 2 in TT3, overall and persistent MDS-CA increased significantly in TT3. Clinical MDS and AML were rarely observed and a full account of hematopathologic findings will be presented.

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Long-term follow-up of autotransplant (AT)-supported high-dose melphalan (hdm) for multiple myeloma (MM): Update of Intergroup Francophone du Myelome (IFM), Southwest Oncology Group (SWOG), and Arkansas (ARK) Total Therapy (TT) trials

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Background: Clinical trial outcomes are usually published when statistical protocol objectives have been met, with short median follow-up not exceeding 5 years. Due to treatment innovations, MM survival beyond 10 years has become more common but formal long-term results are seldom reported. Methods: IFM, SWOG and ARK provide an update of their major trials. IFM-90: 1 AT v standard therapy (STD), IFM-94: 2 v 1 AT, IFM-9902: 2AT ± THAL, IFM-9904: 2AT for high-risk MM; SWOG-9321: 1 AT v STD; TT1: 2 AT with interferon, TT2: 2AT ± THAL, TT3: 2AT + THAL + bortezomib. Results: OS clustered in 3 groups with superior outcomes for TT3/TT2/IFM-99 v TT1 v IFM-94/ IFM-90/SWOG-9321 with 5/10/15-yr estimates of 70%/50%/TE v 57%/35%/20% v 43%/25%/15% (p<0.0001). EFS also clustered in 3 groups with superior outcomes for TT3 v TT2 v remainder with estimates of 71%/TE/TE v 50%/35%/TE v 27%/ 15%/10% (p<0.0001). Among phase III trials, added THAL in TT2 increased 10-yr OS/EFS from 40%/25% to 60%/40% (p=0.04/p=0.0005); 10-yr OS was 30% v 8% with 1 v 0 AT in IFM-90 (p=0.005), 31% v 21% with 2 AT v 1 AT in IFM-94 (p=0.08), and 20% for both arms of S9321. On multivariate analysis involving 2962 patients, OS was adversely affected by B2M >=3.5mg/L (p<0.001), LDH >=ULN (p<0.001), hemoglobin <10g/dL (p=0.001) and albumin <3.5g/dL (p=0.02). 2AT (65%) and THAL (21%) both contributed independently to superior OS (p<0.001, p=0.002); among individual trials, IFM-9902 (19%) and TT2/TT3 (33%) both improved OS significantly (both p<0.001). For each of the 3 major OS clusters, 228 patients could be matched on B2M, LDH, hemoglobin and albumin, with 10-yr OS/EFS estimates of 65%/30% for the TT3/TT2/IFM-9902 group significantly exceeding 30%/15% each for the other 2 groups (p=0.001/p=0.001). Conclusions: A 15-yr EFS plateau of 10% with older trials and superior 10-yr EFS/OS estimates of 50%/35% with recent studies emphasize that cure should be a realistic trial objective in contemporary MM therapy, requiring however very long-term follow-up beyond 15 years.

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A phase II trial of sorafenib in patients with relapsing and resistant multiple myeloma (MM) previously treated with bortezomib (S0434)

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Background: The multikinase inhibitor sorafenib targets several serine/threonine and receptor tyrosine kinases by blocking RAF kinase, a critical component of the RAF/MEK/ERK signaling pathway regulated by the Ras oncogene, which is mutated both in primary patient samples and in human MM lines (35–50%). As the frequency of these mutations increases with advancing disease and increasing drug resistance, inhibition of the RAF/MEK/ERK signaling pathway, as well the angiogenic VEGFR-2/PDGFR beta cascade by sorafenib may be a useful new approach for the treatment of MM. Methods: SWOG evaluated the effect of sorafenib as a single agent in relapsed/refractory MM patients. In this phase II study we assessed response rate, overall (OS) and progression-free survival (PFS) as well as toxicities associated with this treatment. Twenty-three heavily pretreated MM patients were enrolled in the study. Sorafenib was started at oral dose of 400 mg daily until progression or toxicity. This dose was based on the label for metastatic renal cell carcinoma. Results: The study was closed as planned due to lack of efficacy in first 18 patients who were assessable for toxicity and response. Three patients experienced Grade 4 toxicity consisting of thrombocytopenia, anemia and renal failure. 8 cases suffered Grade 3 toxicities including thrombocytopenia, neutropenia, anemia, hand-foot syndrome, diarrhea and dyspnea. No responses were observed. 3 patients had stable disease (2.4–15.9 months) and the remainder progressed. Median PFS is one month, and OS at 12 months is 50%. Conclusions: Thus, single agent sorafenib did not show activity in this group of heavily pretreated MM patients previously exposed to bortezomib. As the frequency of RAS oncogene mutations increases resulting in resistance to traditional chemotherapeutic agents as well as possibly supporting cytokine resistance to immune modulators, sorafenib might have a supportive role in combination therapy with bortezomib, lenalidomide or everolimus in relapsed/refractory MM which is currently being evaluated in ongoing studies.

No significant financial relationships to disclose.

Use of bortezomib (BOR) pharmacogenomics (PG) to identify mechanisms of drug resistance and predict survival in multiple myeloma (MM) treated with total therapy 3 (TT3)

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Background: The prognosis of patients with MM is best captured by gene expression profiling (GEP) analysis of CD138-purified plasma cells (PC), distinguishing a high-risk group of 15% with dismal survival using a 70-gene baseline risk model (BLR). Translational research in TT3 was designed to investigate whether short-term BOR-induced GEP alterations could advance our understanding of BOR's novel mechanism of action. Methods: PG studies were performed as part of two TT3 trials (TT3a, n=303; TT3b, n=177), obtaining PC prior to and 48hr after a BOR test-dose (1.0mg/m2), which was accomplished in 142 patients in TT3a (training set) and 127 in TT3b (test set). Among 1051 genes significantly altered post-BOR in TT3a, 80 were identified as being significantly associated with EFS. A continuous risk score was calculated and an optimal cut-point for EFS separation determined. The independent prognostic power of the binary risk score was tested in TT3b. Multivariate analyses (MV) were employed to determine post-BOR risk (PBR) in relationship to standard prognostic variables and BLR. Results: The discriminatory power in TT3a (3-yr OS: 95% v 45%, p<0.0001; 3-yr EFS: 90% v 35%, p<0.0001) was confirmed in TT3b (18-mo OS: 100% v 65%, p=0.0004; 18-mo EFS: 95% v 45%, p<0.0001). Evaluating PBR in the context of BLR, 12/26 in TT3a and 7/21 in TT3b deemed as having low BLR had high PBR; conversely, 8/126 in TT3a and 14/106 in TT3b deemed as having high BLR had low PBR. In the context of our 8 molecular subgroup model, high PBR was over-represented in the Proliferation (PR) subgroup (7/15 in TT3a, 8/18 in TT3b) and absent in the Low Bone disease (LB) group (0/28). On MV, PBR was an independent adverse variable for both OS and EFS in TT3a (OS: HR=3.17, p=0.006, R2=55%; EFS: HR=4.40, p<0.001, R2=48%) and in TT3b (OS: HR=13.00, p=0.002, R2=48%; EFS: HR=15.57, p<0.001, R2=55%). Proteasome genes ranked first among those differentially up-regulated by BOR. Conclusions: PG identified a powerful 80-gene PBR model with unprecedented prognosis-discriminating power, dispelling BLR from MV analysis by altering BLR designation mainly from low to high risk. High PBR (18%) could be traced to up-regulation of proteasome genes, the target of BOR.

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Prognostic factor analyses of myeloma (MM) survival outcomes on intergroup trial S9321 (int 0141): Examining whether different variables govern different time segments of survival

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Background: MM survival varies enormously from few months to more than a decade. Baseline prognostic factors (PF) have been identified that are linked to survival outcomes, especially B2M and albumin. MM survival plots are typically characterized by 3 segments of slopes with decreasing steepness, suggesting that different PF may govern these time segments. Methods: We therefore examined, in S9321, PF that were associated with overall survival (OS) from baseline (BL) and from 3 subsequent landmarks 3, 5, and 7 years later (LM3, LM5, LM7). With a median follow-up of 9 years, OS and EFS were virtually identical in transplant and standard therapy arms so that the data were pooled. Results: Median OS and EFS for 817 eligible patients are 48 and 22 months. The BL model identified age (>60yr), hemoglobin (<10g/gL), platelet count (<130,000/uL), albumin (<3.5g/dL), B2M (>3.5g/dL), calcium (>10mg/dL), creatinine (>2mg/dL), LDH (>190U/L), performance status (PS, >1), IL-6 level (>140mg/L) and plasma cell labeling index (PCLI, >1%) as being univariately associated with short OS, while age (p=0.002), platelet count (p=0.04), calcium (p<0.001), B2M (p=0.002), LDH (p=0.010) and PCLI (p<0.001) retained significance in multivariate analysis. For the LM3 analyses, age (p=0.006) and B2M (p=0.009) were independently associated with poor OS, whereas PCLI was the only PF associated with LM5 (p=0.026) and age with LM7 (p<0.001). While associated univariately with OS from BL, CRP, platelet count, hemoglobin, albumin, calcium, creatinine, LDH, IL6 and PS all failed to affect OS from later LM times. Conclusions: Whereas the initial 3 years of OS are governed by a combination of features related to disease aggressiveness (LDH, calcium, albumin, CRP), tumor burden (hemoglobin, platelet count) and host tolerance (PS, creatinine), B2M and PCLI as reflectors of tumor burden and proliferation have sustained long-term OS implications. The age factor figures in partly due to death from other causes. In an era of ever-improving survival outcomes, such LM-based PF analysis may reveal trial-specific differences and thus provide guidance toward individualizing therapy.

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Role of T-cell immunity to embryonal stem (ES) cell antigen SOX2 in the progression of myeloma

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Background: Clinical outcome in patients (pts) with asymptomatic plasma-proliferative disorders, monoclonal gammopathy of undetermined significance (MGUS) and asymptomatic myeloma (AMM), is highly variable. There is a need to identify specific tumor or host related features that predict the risk of disease progression. In prior studies, we have shown that patients with MGUS commonly mount a T cell immune response against SOX2, an antigen critical for pluripotency of ES cells. Methods: Patients with MGUS/AMM were enrolled in a prospective observational clinical protocol (SWOG S0120). All patients underwent detailed staging evaluation at registration and were observed without therapy. The presence of T cell immunity to SOX2 in freshly isolated blood / marrow mononuclear cells was analyzed using an overlapping peptide library at study entry. Results: Anti-SOX2 T cell responses were detected in 39/109 (36%) pts tested. Progression to symptomatic MM was observed in only 2 of 39 patients with anti-SOX2 immunity compared to 17 of 59 pts lacking these responses, resulting in 2-yr progression-free survival 96 v 63% (p=0.003). Responses to viral antigens and polyclonal mitogens as controls were preserved in patients lacking SOX2 immunity indicating that the absence of immunity to SOX2 was not due to global immune-suppression. Immunity to SOX2 correlated with features of lower risk including serum-M component < 1.5 g/dL (p=0.008), marrow plasmacytosis < 10% (p<0.001) and normal serum free light chain ratio (p=0.01). Conclusions: These data demonstrate in the context of a prospective trial that T cell immunity to stem cell genes strongly correlates with a reduced risk of progression to clinical myeloma. These data point to SOX2 as a potential target for the prevention of disease progression in MGUS/AMM.

No significant financial relationships to disclose.

Gene expression profiling (GEP)-defined risk and molecular subgroups assessed at baseline and at relapse: Collective impact on post-relapse survival of multiple myeloma (MM) treated with total therapies 2 and 3

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Background: GEP-defined risk has evolved as the most robust predictor of overall and event-free survival (OS, EFS) in MM with TT2 and TT3 protocols, distinguishing 85% with low-risk (LR) and 15% with high-risk (HR). Upon relapse, the original risk designation may change typically in the direction LR to HR. Here we examine, among patients with available GEP data at baseline (BL) and relapse (REL), the contributions of both observations on post-relapse survival (PRS). Methods: Paired REL-BL GEP data were available in 77 patients, while information on metaphase cytogenetic abnormalities (CA) was obtained in 76 patients at both time-points. Results: PRS was significantly affected by both BL and REL HR status so that, among the 52 patients with LR at BL, HR status at REL conferred significantly poorer outcome compared to those with LR at REL (p=0.0005) with 30-mo estimates of 71% v 13%; likewise, among the 25 patients with HR at baseline, HR present also at relapse further diminished PRS (p=0.09) with 30-mo estimates in both settings of less than 20%. Similar considerations for CA status revealed, among the 29 patients without CA at BL, marked attrition of PRS with CA v no CA at REL with 30-mo estimates of 29% v 81% (p=0.04); for the 47 patients with CA at BL, CA also at REL further diminished the poor PRS from 46% to 22% (p=0.06). When all standard BL and REL prognostic factors were examined in a multivariate model, GEP-derived HR contributed to poor PRS both when present at BL (HR=2.79, p=0.005) and at REL (HR=2.77, p=0.002), in addition to CA at BL (HR=2.44, p=0.018). Conclusions: In estimating PRS in TT protocols, genetic characteristics at BL (HR, CA) have enduring adverse consequences aggravated further by HR status at REL. Therefore, in HR/CA BL settings, aiming at REL prevention appears as the best overall treatment strategy.

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