The bone-marrow niche in MDS and MGUS: implications for AML and MM

Several haematological malignancies, including multiple myeloma (MM) and acute myeloid leukaemia (AML), have well-defined precursor states that precede the development of overt cancer. MM is almost always preceded by monoclonal gammopathy of undetermined significance (MGUS), and at least a quarter of all patients with myelodysplastic syndromes (MDS) have disease that evolves into AML. In turn, MDS are frequently anteceded by clonal haematopoiesis of indeterminate potential (CHIP). The acquisition of additional genetic and epigenetic alterations over time clearly influences the increasingly unstable and aggressive behaviour of neoplastic haematopoietic clones; however, perturbations in the bone-marrow microenvironment are increasingly recognized to have key roles in initiating and supporting oncogenesis. In this Review, we focus on the concept that the haematopoietic neoplasia-microenvironment relationship is an intimate rapport between two partners, provide an overview of the evidence supporting a role for the bone-marrow niche in promoting neoplasia, and discuss the potential for niche-specific therapeutic targets.

Treatment of relapsed/refractory multiple myeloma

The introduction of several novel and active treatments and improvements in supportive care of myeloma patients has resulted in a prolongation of the survival of these patients. However, myeloma remains an incurable disease and almost all patients will relapse. Effective management of the relapsing/refractory disease incorporates several different strategies, depending on prior treatments, responses, and duration of responses, as well as residual toxicity, age, and physical condition. High-dose dexamethasone still has a role in the management of disease complications such as cytopenias, renal impairment, or spinal cord compression until another agent is added. High-dose therapy may be considered for selected patients who have a long-term treatment-free interval after their first transplantation. Allogeneic transplantation is limited to selected young patients, preferably with an HLA-matched donor. However, the backbone of current strategies for the management of relapsed/refractory myeloma includes the novel agents thalidomide, bortezomib, and lenalidomide. These agents, either with dexamethasone or in combination with chemotherapy, have shown significant activity both in relapsed and in refractory patients. Based on the results of phase III trials, lenalidomide and bortezomib have increased the post-relapse survival and are active in patients who have received prior novel agents; lenalidomide is active in thalidomide-pretreated or bortezomib-pretreated patients and bortezomib alone or in combination with chemotherapy is active in thalidomide/lenalidomide-pretreated patients. Combinations of novel agents show synergistic activity and may overcome drug resistance. Finally, special consideration is needed for the management of patients with renal impairment or other poor prognostic features.

Beyond monoclonal antibodies: new therapeutic agents in non-Hodgkin's lymphomas

The availability of active monoclonal antibodies, either as single agents or in combination with cytotoxic agents, has improved treatment results in non-Hodgkin's lymphoma (NHL). Despite this and the increasing number of available active monoclonal antibodies, alone or conjugated with radioisotopes, not all types of lymphoma are sensitive to these biological agents and often they become resistant because of different molecular mechanisms. New molecular targets in neoplastic cells are emerging and provide the rationale for novel discovery initiatives. In fact, a greater knowledge of the biology of lymphoma and the identification of compounds selectively active against a potential therapeutic pathway have already improved the time to progression and survival time of patients with some subtypes of NHL. The growing list of new drugs provides the exciting prospect of developing disease-specific and even patient-specific therapies. The aim of this review is to identify and discuss non-monoclonal antibody new therapeutic agents in terms of mechanism of action and clinical results. The preclinical and clinical features of proteasome inhibitors, histone deacetylase inhibitors, thalidomide and lenalidomide, mammalian target of rapamycin inhibitors, antisense oligonucleotides, heat shock protein inhibitors, protein kinase C inhibitors, antiangiogenic agents, and new cytotoxics are reviewed.

Clinical biomarkers of angiogenesis inhibition

INTRODUCTION

An expanding understanding of the importance of angiogenesis in oncology and the development of numerous angiogenesis inhibitors are driving the search for biomarkers of angiogenesis. We review currently available candidate biomarkers and surrogate markers of anti-angiogenic agent effect.

DISCUSSION

A number of invasive, minimally invasive, and non-invasive tools are described with their potential benefits and limitations. Diverse markers can evaluate tumor tissue or biological fluids, or specialized imaging modalities.

CONCLUSIONS

The inclusion of these markers into clinical trials may provide insight into appropriate dosing for desired biological effects, appropriate timing of additional therapy, prediction of individual response to an agent, insight into the interaction of chemotherapy and radiation following exposure to these agents, and perhaps most importantly, a better understanding of the complex nature of angiogenesis in human tumors. While many markers have potential for clinical use, it is not yet clear which marker or combination of markers will prove most useful.

lenalidomide enhances natural killer cell and monocyte-mediated antibody-dependent cellular cytotoxicity of rituximab-treated CD20+ tumor cells

PURPOSE

Lenalidomide has significant activity in myelodysplastic syndromes, multiple myeloma, and non-Hodgkin's lymphoma (NHL). In previous studies, natural killer (NK) cell expansion by lenalidomide was shown to enhance the cytotoxic effect of rituximab. This study assessed the ability of lenalidomide to enhance antibody-dependent cellular cytotoxicity (ADCC) in rituximab-treated NHL cell lines and primary tumor cells from patients with B-cell chronic lymphocytic leukemia (B-CLL) in vitro.

EXPERIMENTAL DESIGN

An in vitro ADCC system was used to assess the ability of lenalidomide to enhance human NK cell and monocyte function in response to rituximab.

RESULTS

Lenalidomide directly enhanced IFN-gamma production via Fc-gamma receptor-mediated signaling in response to IgG. It was also a potent enhancer of NK cell-mediated and monocyte-mediated tumor cell ADCC for a variety of rituximab-treated NHL cell lines in vitro, an effect that was dependent on the presence of antibody and either interleukin-2 or interleukin-12. Lenalidomide also enhanced the ability of NK cells to kill primary tumor cells derived from three patients with B-CLL who have been treated previously with fludarabine plus cyclophosphamide. Enhanced NK cell ADCC was associated with enhanced granzyme B and Fas ligand expression and could be inhibited by a granzyme B inhibitor and partially inhibited by antibody to FasL. Enhanced NK cell Fc-gamma receptor signaling is associated with enhanced phosphorylated extracellular signal-related kinase levels leading to enhanced effector function.

CONCLUSIONS

These findings suggest that lenalidomide has the potential to enhance the rituximab-induced killing of NHL cell lines and primary B-cell chronic lymphocytic leukemia cells via a NK cell-mediated and monocyte-mediated ADCC mechanism in vitro, providing a strong rationale for the combination of lenalidomide with IgG1 antibodies to target tumor-specific antigens in patients with cancer.

Phase I-II trial of bortezomib plus oral cyclophosphamide and prednisone in relapsed and refractory multiple myeloma

PURPOSE

The combination of oral weekly cyclophosphamide and alternate day prednisone is a convenient regimen for relapsed/refractory multiple myeloma (MM), and we sought to improve its efficacy by adding bortezomib, a proteasome inhibitor with proven antimyeloma activity.

PATIENTS AND METHODS

We conducted a phase I-II trial evaluating six dose levels to define the maximum tolerated dose (MTD) of this combination in relapsed/refractory MM. An additional 10 patients were evaluated at the highest dose level reached.

RESULTS

Thirty-seven patients were treated on this study. The MTD was not defined. Both of the highest dose levels of bortezomib tested (1.3 mg/m(2) on days 1, 4, 8, and 11 and 1.5 mg/m(2) on days 1, 8, and 15, each on a 28-day cycle) could be safely given with cyclophosphamide 300 mg/m(2) per week and prednisone. At these dose levels, the overall response rate was 95% (complete responses [CR] plus partial response plus minimal response), with CR observed in more than 50% of patients. The weekly bortezomib regimen resulted in fewer instances of grade 3 thrombocytopenia and grade 1 to 2 peripheral neuropathy; the 1-year progression-free and overall survival probabilities with this dose level were 83% (95% CI, 73% to 96%) and 100%, respectively.

CONCLUSION

Weekly bortezomib 1.5 mg/m(2) plus oral cyclophosphamide and prednisone produces an unprecedented response rate and encouraging 1-year survival in relapsed/refractory patients with MM. Further evaluation of this promising regimen is warranted both in relapsed and newly diagnosed disease.

Non-thromboembolic pulmonary hypertension in multiple myeloma, after thalidomide treatment: a pilot study

BACKGROUND

Multiple myeloma (MM) is thrombogenic as a consequence of multiple hemostatic effects and endothelial damage. Thalidomide has been associated with an increased risk of thromboembolic pulmonary hypertension (PH). PH in the absence of venous thromboembolism has also been described in MM patients during thalidomide treatment.

AIM

Detection of clinical and subclinical nonthromboembolic PH in MM patients after thalidomide treatment.

PATIENTS AND METHODS

Eighty-two patients, 46-82 years (median age 61 years), 42 males, were studied. They underwent echocardiographic study at baseline, 1 month thereafter, 6 months later and whenever symptoms indicating deterioration of cardiac function appeared. Echocardiographic signs of PH were especially identified.

RESULTS

Clinical and echocardiographic evaluation revealed four patients (out of 82 patients, 4.87%) with PH. Nonimaging and imaging diagnostic methods excluded thromboembolic PH. Statistical analysis demonstrated significant correlation between structural heart disease and PH (r = 14.078; P = 0.008). No significant correlation between age (r = 0.770; P = 0.724), gender (r = 1.157; P = 0.285), International Staging System (ISS) (r = 0.316; P = 0.716) and PH was found.

CONCLUSIONS

Preexisted endothelial dysfunction due to structural cardiac disease enhances the vasoactive substances release causing increased pulmonary vascular resistance. Thalidomide possibly causes a vasodilator and vasoconstriction imbalance, which may cause abnormal pulmonary vascular response interfering to a vicious circle perpetuating PH.

[New therapeutic strategies for multiple myeloma. Efficacy and cost-effectiveness analyses]

The objective of the present article is the review of the most important therapeutic innovations in the treatment of multiple myeloma in terms of efficacy and cost-effectiveness. Besides autologous transplant with peripheral-blood stem-cell, thalidomide establishes as one of the most powerful therapeutic tools in induction and maintenance treatment and together with lenalidomide and bortezomib as therapy for relapsing/refractory multiple myeloma. Considering, the last named situation thalidomide can be an adequate therapeutical option in combination with dexamethasone. Under a strictly pharmacoeconomic point of view, lenalidomide and bortezomib seem to be additional alternatives in patients previously treated with thalidomide.

Current Trends in Multiple Myeloma Management

Treatment of multiple myeloma, a B-cell cancer, is usually palliative, however, as a result of intensive clinical research there are numerous new treatment options available today. The present review summarizes non-transplant treatment options for multiple myeloma on the basis of available publications. Treatment with new substances, such as immunomodulatory agents, farnesyl transferase inhibitors and apoptosis stimulators, and their mechanisms of action are discussed. In addition to this systematic review of the available evidence on multiple myeloma therapy we have also summarized current recommendations from national and international organizations on aspects of the treatment of multiple myeloma. This should enable readers to see different points of view at a glance and, hopefully, will provide a basis for translation of the available evidence into the best possible therapy.

Lenalidomide for the treatment of B-cell malignancies

Lenalidomide is a novel anticancer agent that has made a major impact in the treatment of patients with B-cell malignancies. A more potent analog of thalidomide, lenalidomide was developed to enhance immunomodulatory properties with improved safety profile. Its antitumor activity seems mediated through modulation of both the cytokine and cellular tumor cell microenvironment. Preclinical as well as clinical observations demonstrate that lenalidomide downregulates production of various critical prosurvival cytokines in the tumor microenvironment while concurrently promoting activation of T- and natural killer (NK) cell-mediated antitumor response. Early clinical investigations noted its efficacy in relapsed and/or refractory multiple myeloma patients. Subsequently, larger randomized studies confirmed the clinical benefit of lenalidomide when added to dexamethasone compared with dexamethasone alone in previously treated myeloma patients resulting in its recent approval by the US Food and Drug Administration. Consequently, the role of lenalidomide in other B-cell malignancies has been investigated, with impressive results in chronic lymphocytic leukemia and non-Hodgkin's lymphoma. This review summarizes the data from various clinical investigations and highlights the impact of lenalidomide in the management of patients with B-cell malignancies.

Management of relapsed and relapsed refractory myeloma

Studies of bortezomib, thalidomide, and lenalidomide have shown promising clinical activity in relapsed/refractory multiple myeloma (MM). Bortezomib alone and in combination with other agents is associated with high response rates, consistently high rates of complete response, and a predictable and manageable profile of adverse events. Thalidomide-based regimens have also shown substantial clinical activity. The accumulating experience from ongoing trials of bortezomib/lenalidomide/dexamethasone combinations in patients who have relapsed/refractory or newly diagnosed MM will provide critical information that will determine the possible role of this combination as the basic backbone for combination regimens for management of advanced MM.

Lenalidomide in myelodysplastic syndrome and multiple myeloma

The use of thalidomide is limited by adverse effects of sedation, constipation, neuropathy and thromboembolism. In order to discover more potent and less toxic immunomodulators than thalidomide, its chemical structure was modified and lenalidomide was formed. Lenalidomide is approved by the US FDA for the treatment of patients with low-risk myelodysplastic syndrome (MDS) with deletion 5q cytogenetic abnormality. Two studies and a case report have evaluated lenalidomide in these MDS patients and showed significantly higher cytogenetic responses and durable red blood cell transfusion independence. Lenalidomide should be the drug of choice for patients with low and intermediate-1 risk MDS (based on the International Prognostic Scoring System) with chromosome 5q31 deletion with or without other karyotype abnormalities. Lenalidomide, in combination with dexamethasone, has been compared with dexamethasone alone in patients with relapsed or refractory multiple myeloma (MM) in two studies (MM-009 in North America and MM-010 in Europe, Israel and Australia). In these two phase III trials, lenalidomide demonstrated impressive (58-59%) response rates with dexamethasone. Lenalidomide has also been shown to overcome thalidomide resistance in MM patients. Therefore, the lenalidomide plus dexamethasone regimen provides another treatment option, in addition to first line MM treatment regimens of bortezomib, thalidomide or high-dose dexamethasone, for the treatment of relapsed or refractory MM. Lenalidomide does not produce significant sedation, constipation or neuropathy, but does lead to significant myelosuppression, unlike thalidomide. The prescribing information has a black box warning for risk of myelosuppression, deep vein thrombosis/pulmonary embolism and teratogenicity. Administration of lenalidomide is recommended at a starting dose of 10 mg/day orally for deletion 5q in MDS patients. Significant risk of myelosuppression may lead to dose reduction in the majority of these patients. Clinical trials of relapsed and refractory MM have shown that lenalidomide is clinically efficacious at a dosage of 25 mg/day when administered in combination with dexamethasone. Lenalidomide should be continued until disease progression in both MDS and MM patients.

From the bench to the bedside: emerging new treatments in multiple myeloma

Within the last decade, several novel classes of anti-myeloma therapeutics have become available. The clinical successes achieved by thalidomide, lenalidomide, and the proteasome inhibitor bortezomib, and in particular the ability of these agents to lead to major clinical responses in patients resistant to conventional or high-dose chemotherapy, have highlighted the importance of expanding further the spectrum of classes of agents utilized for the treatment of myeloma. Herein, we review the current status for the development of novel anti-myeloma agents, with emphasis on classes of therapeutics which have already translated into clinical trials or those in advanced stages of preclinical development. These include second-generation proteasome inhibitors (NPI-0052 and PR-171), heat shock protein 90 (hsp90) inhibitors, 2-methoxyestradiol, histone deacetylase (HDAC) inhibitors (e.g. SAHA and LBH589), fibroblast growth factor receptor 3 (FGF-R3) inhibitors, insulin-like growth factor 1 receptor (IGF-1R) inhibitors, mTOR inhibitors, monoclonal antibodies, and agents specifically targeting the tumor microenvironment, such as defibrotide.

Clinically relevant end points and new drug approvals for myeloma

This manuscript summarizes the recommendations of the American Society of Hematology/US Food and Drug Administration Workshop on Clinical Endpoints in Multiple Myeloma, which brought together clinical investigators in multiple myeloma, the United States Food and Drug Administration, pharmaceutical companies, patient advocates and other concerned scientists and physicians to provide guidance, consensus and consistency in the definition of clinically relevant end points to expedite new drug approvals for multiple myeloma in the appropriate trial design settings. This manuscript will therefore be a most valuable resource to provide the framework for the design of appropriate clinical trial strategies for more rapid new drug approval in myeloma.

New drugs for myeloma

Although multiple myeloma remains incurable with conventional treatments, management of the disease has recently been transformed with the introduction of three novel agents, bortezomib, thalidomide, and lenalidomide. The proteasome inhibitor bortezomib is approved for the treatment of patients who have received one prior therapy; there is a growing body of clinical evidence showing its effectiveness alone and in combination in the frontline setting, with high response rates and consistently high rates of complete response. Thalidomide plus dexamethasone is approved as frontline treatment of multiple myeloma. Other combination regimens including thalidomide have demonstrated substantial activity in both relapsed and frontline settings. Recently, the thalidomide analogue lenalidomide has been approved, in combination with dexamethasone, for the treatment of patients who have received one prior therapy; this regimen has shown promising results in the frontline setting. These agents represent a new generation of treatments for multiple myeloma that affect both specific intracellular signaling pathways and the tumor microenvironment. Other novel, targeted therapies are also being evaluated in preclinical and clinical studies. Regimens incorporating bortezomib, thalidomide, lenalidomide, and other novel agents, together with commonly used conventional drugs, represent a promising future direction in myeloma treatment. At present, further investigation is required to assess the safety and activity of combinations integrating these other novel agents. However, bortezomib, thalidomide, and lenalidomide are now in widespread clinical use. This review therefore focuses on the extensive clinical data available from studies of these drugs in the treatment of newly diagnosed and advanced multiple myeloma.

Melphalan, prednisone, and lenalidomide treatment for newly diagnosed myeloma: a report from the GIMEMA--Italian Multiple Myeloma Network

PURPOSE

Lenalidomide has shown significant antimyeloma activity in clinical studies. Oral melphalan, prednisone, and thalidomide have been regarded as the standard of care in elderly multiple myeloma patients. We assessed dosing, efficacy, and safety of melphalan, prednisone, and lenalidomide (MPR) in newly diagnosed elderly myeloma patients.

PATIENTS AND METHODS

Oral melphalan was administered in doses ranging from 0.18 to 0.25 mg/kg on days 1 to 4, prednisone at a 2-mg/kg dose on days 1 to 4, and lenalidomide at doses ranging from 5 to 10 mg on days 1 to 21, every 28 days for nine cycles, followed by maintenance therapy with lenalidomide alone. Aspirin was given as a prophylaxis for thrombosis.

RESULTS

Fifty-four patients were enrolled and evaluated after completing the assigned treatment schedule. The maximum tolerated dose was defined as 0.18 mg/kg melphalan and 10 mg lenalidomide. With these doses, 81% of patients achieved at least a partial response, 47.6% achieved a very good partial response, and 23.8% achieved a complete immunofixation-negative response. In all patients, 1-year event-free and overall survival rates were 92% and 100%, respectively. At the maximum tolerated dose, grade 3 adverse events included neutropenia (38.1%), thrombocytopenia (14.2%), febrile neutropenia (9.5%), vasculitis (9.5%), and thromboembolism (4.8%); grade 4 adverse events were neutropenia (14.2%) and thrombocytopenia (9.5%).

CONCLUSION

Oral MPR therapy is a promising first-line treatment for elderly myeloma patients. Hematologic adverse events were frequent but manageable. A low incidence of nonhematologic adverse events was noted. Aspirin appears to provide adequate antithrombosis prophylaxis.

The thalidomide saga

Over the past 50 years, thalidomide has been a target of active investigation in both malignant and inflammatory conditions. Although initially developed for its sedative properties, decades of investigation have identified a multitude of biological effects that led to its classification as an immunomodulatory drug (IMiD). In addition to suppression of tumor necrosis factor-alpha (TNF-alpha), thalidomide effects the generation and elaboration of a cascade of pro-inflammatory cytokines that activate cytotoxic T-cells even in the absence of co-stimulatory signals. Furthermore, vascular endothelial growth factor (VEGF) and beta fibroblast growth factor (bFGF) secretion and cellular response are suppressed by thalidomide, thus antagonizing neoangiogenesis and altering the bone marrow stromal microenvironment in hematologic malignancies. The thalidomide analogs, lenalidomide (CC-5013; Revlimid) and CC-4047 (Actimid), have enhanced potency as inhibitors of TNF-alpha and other inflammatory cytokines, as well as greater capacity to promote T-cell activation and suppress angiogenesis. Both thalidomide and lenalidomide are effective in the treatment of multiple myeloma and myelodysplastic syndromes for which the Food and Drug Administration granted recent approval. Nonetheless, each of these IMiDs remains the subject of active investigation in solid tumors, hematologic malignancies, and other inflammatory conditions. This review will explore the pharmacokinetic and biologic effects of thalidomide and its progeny compounds.

The treatment of the elderly multiple myeloma patients

Multiple myeloma (MM) is an incurable malignancy of the plasma cells. Most patients are diagnosed when they are older than 65 years. Therapeutic options include chemotherapy, using either established (e.g. melphalan) or newly available (e.g. thalidomide) drugs and high-dose treatment with stem-cell support (autologous as well as allogeneic). Recent research has focused on defining the target population for the different therapeutic approaches, taking into account pre-treatment characteristics of patients, particularly age, and aims to balance treatment benefit with potential adverse events. In this review we present the data available on the most recent trials dealing with the treatment of elderly MM patients.

[New treatment of multiple myeloma]

PURPOSE

After decades of minimal progress, two new classes of drugs with novels mechanisms of action: immunomodulatory drugs (thalidomide and lenalidomide) and proteasome inhibitors (bortezomib) have shown great activity for the treatment of multiple myeloma.

CURRENT KNOWLEDGE AND KEY POINTS

Thalidomide acts by a variety of mechanisms; its efficacy is well known in disease relapse especially associated with dexamethasone. Recent results prove that combination of thalidomide with melphalan and prednisone should be considered as the first line standard of care in elderly patient. The main side effects are peripheral neuropathy and deep-vein thrombosis. Bortezomib is the first proteasome inhibitor. It is approved for the treatment in first disease relapse. The combination with glucocorticoids is synergistic. This combination in induction treatment before autologous stem cell transplantation is promising, as well as the combination with melphalan and prednisone in elderly patient. The main toxicities are fatigue and peripheral neuropathy. Lenalidomide is a structural analogue of thalidomide. Its efficacy in combination with dexamethasone has been proved in relapsing patients. The main toxicity is hematologic. Utilisation as first line treatment is also promising.

FUTURE PROSPECTS AND PROJECTS

These three drugs have toxicities predictable and manageable and can be used successively or in combination for greater effectiveness. They have an impact on the multiple myeloma treatment strategies and on the disease course itself.

Targeted therapeutics for multiple myeloma: The arrival of a risk-stratified approach

Multiple myeloma (MM) remains an incurable hematologic malignancy characterized by frequent early responses, inevitably followed by treatment relapse. Until recently, few effective therapies existed. Indeed, the use of alkylating agents and corticosteroids had remained the treatment of choice for almost four decades. Several novel agents for MM have now become available, including the immunomodulatory drugs thalidomide and lenalidomide, as well as the proteasome inhibitor bortezomib. Each of these agents is undergoing extensive clinical evaluation in combination with other therapies to produce unprecedented response rates in newly diagnosed and relapsed MM. Nevertheless, relapse remains universal and further therapeutics with broad activity are required. Importantly, it has become clear that pivotal genetic events are the primary harbingers of clinical outcome and novel targeted therapy approaches using existing approved drugs or novel agents, which address that disrupted signaling pathways are now in various stages of clinical testing. It seems increasingly likely that novel drug combinations, which together turn off these critical Achilles heels, will become the standard of care and that treatment will become increasingly personalized and guided by genetic testing and prognostic factors.

Risk of Thrombosis With Lenalidomide and Its Prevention With Aspirin

Lenalidomide, an analog of thalidomide, is an effective new treatment for multiple myeloma. Both compounds are associated with an increased risk of venous thromboembolism, particularly when used in combination with high-dose dexamethasone. As new trials with lenalidomide are being planned and performed, investigators are placing high importance on reducing the risk of thrombosis by incorporating an antithrombotic agent into the therapeutic regimen. Low-molecular-weight heparin, warfarin, and aspirin have all been suggested as candidate drugs for thromboprophylaxis, but none of these agents have been evaluated in randomized clinical trials. A body of opinion has evolved that aspirin is very effective in preventing venous thrombosis in myeloma patients treated with lenalidomide. If correct, this view has important implications, because aspirin is inexpensive and is safer and more convenient than anticoagulants. On the other hand, aspirin is less effective than anticoagulants for preventing venous thrombosis in other high-risk groups, and therefore might not be the most appropriate choice for preventing of venous thrombosis in myeloma patients. This commentary examines the strength of the evidence supporting the effectiveness of aspirin in preventing venous thrombosis in multiple myeloma patients treated with lenalidomide. It is concluded that the evidence that aspirin is efficacious in preventing venous thrombosis in myeloma patients is based on "before/after" and retrospective studies, with potential for bias and confounders. There is, therefore, a critical need to incorporate a randomized comparison of aspirin with an anticoagulant in future trials evaluating lenalidomide in multiple myeloma.