Safety of low-dose low-molecular-weight-heparins in thrombocytopenic stem cell transplantation patients: a case series and review of the literature

Single center evaluation on the use of conditionally ordered low molecular weight heparins in malignant hematology patients with venous thromboembolism

BACKGROUND

Cancer and cancer-related treatments are significant independent risk factors for malignant hematology (MH) patients in developing venous thromboembolism (VTE). Treatment of VTE in MH patients at the Princess Margaret Cancer Centre is predominantly initiated with low molecular weight heparin (LMWH) in accordance with guidelines. While guidelines recommend against LMWH use in patients with thrombocytopenia, prescribers may order LMWH conditionally based on platelet values. Currently, there is a lack of consistent practice with variation in both the use of conditional orders as well as the threshold of platelet values for conditional orders. The objectives of the study were to (a) describe the use of conditionally ordered LMWH based on platelet values; (b) determine its safety by measuring administration concordance with conditional orders and bleeding event rates during inpatient admission; and (c) determine its efficacy by measuring the rate of worsening VTE or recurrence during inpatient admission.

METHODS

Electronic records of MH inpatients admitted between January 2017 and December 2019 and who were administered at least one dose of an LMWH for the treatment of VTE were screened.

RESULTS

One hundred and eight patients were screened to obtain 50 eligible patients with a median age of 59 years (SD = ±18.8 years). The most frequent MH diagnosis was acute lymphoblastic leukemia (30%). Sixty percent (n = 30) of patients received conditional orders. Out of 571 administrations, 543 (95%) were administered concordantly (Χ2(1) = 472, p < 0.0001). In this group of patients, 8 patients had either documented bleeding or experienced a drop in hemoglobin >10 g/L within a 72 h time frame. No patients experienced a recurrent VTE during inpatient treatment (for up to 40 days post-admission).

CONCLUSIONS

It appears that conditionally ordered LMWH can be concordantly administered and is safe and effective in the treatment of VTE in MH patients experiencing thrombocytopenia. There were no reports of worsening or new VTE in our small sample.

[Translation into French and republication of: "Management of cancer-associated thromboembolism in vulnerable population"]

Although all patients with cancer-associated thrombosis (CAT) have a high morbidity and mortality risk, certain groups of patients are particularly vulnerable. This may expose the patient to an increased risk of thrombotic recurrence or bleeding (or both), as the benefit-risk ratio of anticoagulant treatment may be modified. Treatment thus needs to be chosen with care. Such vulnerable groups include older patients, patients with renal impairment or thrombocytopenia, and underweight and obese patients. However, these patient groups are poorly represented in clinical trials, limiting the available data on which treatment decisions can be based. Meta-analysis of data from randomised clinical trials suggests that the relative treatment effect of direct oral factor Xa inhibitors (DXIs) and low molecular weight heparin (LMWH) with respect to major bleeding could be affected by advanced age. No evidence was obtained for a change in the relative risk-benefit profile of DXIs compared to LMWH in patients with renal impairment or of low body weight. The available, albeit limited, data do not support restricting the use of DXIs in patients with TAC on the basis of renal impairment or low body weight. In older patients, age is not itself a critical factor for choice of treatment, but frailty is such a factor. Patients over 70 years of age with CAT should undergo a systematic frailty evaluation before choosing treatment and modifiable bleeding risk factors should be addressed. In patients with renal impairment, creatine clearance should be assessed and monitored regularly thereafter. In patients with an eGFR less than 30mL/min/1.72m2, the anticoagulant treatment may need to be adapted. Similarly, platelet count should be assessed prior to treatment and monitored regularly. In patients with grade 3-4, thrombocytopenia (less than 50,000platelets/μL) treatment with a LMWH at a reduced dose should be considered. For patients with CAT and low body weight, standard anticoagulant treatment recommendations are appropriate, whereas in obese patients, apixaban may be preferred.

Management of cancer-associated thromboembolism in vulnerable population

Although all patients with cancer-associated thrombosis (CAT) have a high morbidity and mortality risk, certain groups of patients are particularly vulnerable. This may expose the patient to an increased risk of thrombotic recurrence or bleeding (or both), as the benefit-risk ratio of anticoagulant treatment may be modified. Treatment thus needs to be chosen with care. Such vulnerable groups include older patients, patients with renal impairment or thrombocytopenia, and underweight and obese patients. However, these patient groups are poorly represented in clinical trials, limiting the available data, on which treatment decisions can be based. Meta-analysis of data from randomised clinical trials suggests that the relative treatment effect of direct oral factor Xa inhibitors (DXIs) and low molecular weight heparin (LMWH) with respect to major bleeding could be affected by advanced age. No evidence was obtained for a change in the relative risk-benefit profile of DXIs compared to LMWH in patients with renal impairment or of low body weight. The available, albeit limited, data do not support restricting the use of DXIs in patients with CAT on the basis of renal impairment or low body weight. In older patients, age is not itself a critical factor for choice of treatment, but frailty is such a factor. Patients over 70 years of age with CAT should undergo a systematic frailty evaluation before choosing treatment and modifiable bleeding risk factors should be addressed. In patients with renal impairment, creatine clearance should be assessed and monitored regularly thereafter. In patients with an eGFR<30mL/min/1.72m2, the anticoagulant treatment may need to be adapted. Similarly, platelet count should be assessed prior to treatment and monitored regularly. In patients with grade 3-4, thrombocytopenia (<50,000 platelets/μL) treatment with a LMWH at a reduced dose should be considered. For patients with CAT and low body weight, standard anticoagulant treatment recommendations are appropriate, whereas in obese patients, apixaban may be preferred.

Evaluation of venous thromboembolism prophylaxis protocol in hematopoietic cell transplant patients

Hematopoietic cell transplant (HCT) recipients are at risk for thromboembolic and bleeding complications. There is limited evidence regarding the optimal approach to managing venous thromboembolism (VTE) prophylaxis in hospitalized patients undergoing HCT. In this retrospective cohort study, we evaluated the incidence of bleeding and VTE events in hospitalized HCT patients who received VTE prophylaxis per our institution's VTE Prophylaxis Protocol (VPP), with either enoxaparin 40 mg subcutaneously daily or heparin 5 000 units subcutaneously twice daily, compared to historical controls who did not receive VTE prophylaxis. The primary outcome was a composite of major bleeding events, clinically relevant non-major bleeding (CRNMB), and minor bleeding. The secondary outcome was a composite of VTE events. A total of 614 patients were evaluated, including 278 prior to and 336 after implementation of VPP. VTE prophylaxis resulted in no difference in bleeding events (15.1% in the pre-VPP group vs. 14.6% in the post-VPP group, p = 0.86) or composite of major and CRNMB events (0.72% vs. 0.30%, p = 0.59). There was a trend toward lower incidence of VTE events in the post-VPP group which did not reach statistical significance (8.6% vs. 6.0%, p = 0.20). We conclude that VTE prophylaxis does not pose additional bleeding risk in HCT patients.

Anticoagulation management and related outcomes in patients with cancer-associated thrombosis and thrombocytopenia: A systematic review and meta-analysis

BACKGROUND

Patients with cancer have an increased risk of both venous thromboembolism (VTE) requiring anticoagulation and thrombocytopenia. The optimal management is unclear. We performed a systematic review and meta-analysis to evaluate the outcomes in these patients.

METHODS

We searched MEDLINE, Embase, Scopus, and Cochrane Central Register of Controlled Trials from inception to February 5, 2022. Studies assessing adult patients with cancer-associated thrombosis and platelet count <100 × 10⁹/L were included. Three anticoagulation management strategies were reported: full dose, modified dose, or no anticoagulation. The primary efficacy outcome was recurrent VTE, and the primary safety outcome was major bleeding. The incidence rates of thrombotic and bleeding outcomes by anticoagulation management strategies were descriptive, and were pooled using random effects model and expressed as events per 100 patient-months with associated 95 % confidence intervals (CI).

RESULTS

We included 19 observational cohort studies (N = 1728 patients) in the systematic review, with 10 included in the meta-analysis (N = 707 patients). Approximately 90 % of patients had hematological malignancies, with low-molecular-weight heparin being the main anticoagulant. The rates of recurrent VTE and bleeding complications were high regardless of management strategies - recurrent VTE on full dose: 2.65/100 patient-months (95 % CI 1.62-4.32), modified dose: 3.51/100 patient-months (95 % CI 1.00-12.39); major bleeding on full dose: 4.45/100 patient-months (95 % CI 2.80-7.06), modified dose: 4.16/100 patient-months (95 % CI 2.24-7.74). There was serious risk of bias in all studies.

CONCLUSIONS

Patients with cancer-associated thrombosis and thrombocytopenia have high risks of both recurrent VTE and major bleeding, but current literature is significantly limited to guide the best management.

Current management of cancer-associated venous thromboembolism in patients with thrombocytopenia: a retrospective cohort study

Optimal management of venous thromboembolism (VTE) in cancer patients with thrombocytopenia is uncertain. We described current management and clinical outcomes of these patients. We retrospectively included a cohort of cancer patients with acute VTE and concomitant mild (platelet count 100,000-150,000/mm³), moderate (50,000-99,000/mm³), or severe thrombocytopenia (< 50,000/mm³). Univariate and multivariate logistic regression analyses explored the association between different therapeutic strategies and thrombocytopenia. The incidence of VTE and bleeding complications was collected at a 3-month follow-up. A total of 194 patients of whom 122 (62.89%) had mild, 51 (26.29%) moderate, and 22 (11.34%) severe thrombocytopenia were involved. At VTE diagnosis, a full therapeutic dose of LMWH was administered in 79.3, 62.8 and 4.6% of patients, respectively. Moderate (OR 0.30; 95% CI 0.12-0.75), severe thrombocytopenia (OR 0.01; 95% CI 0.00-0.08), and the presence of cerebral metastasis (OR 0.06; 95% CI 0.01-0.30) were independently associated with the prescription of subtherapeutic LMWH doses. Symptomatic VTE (OR 4.46; 95% CI 1.85-10.80) and pulmonary embolism (OR 2.76; 95% CI 1.09-6.94) were associated with the prescription of full therapeutic LMWH doses. Three-month incidence of VTE was 3.9% (95% CI 1.3-10.1), 8.5% (95% CI 2.8-21.3), 0% (95% CI 0.0-20.0) in patients with mild, moderate, and severe thrombocytopenia, respectively. The corresponding values for major bleeding and mortality were 1.9% (95% CI 0.3-7.4), 6.4% (95% CI 1.7-18.6), 0% (95% CI 0.0-20.0) and 9.6% (95% CI 5.0-17.4), 48.2% (95% CI 16.1-42.9), 20% (95% CI 6.6-44.3). In the absence of sound evidence, anticoagulation strategy of VTE in cancer patients with thrombocytopenia was tailored on an individual basis, taking into account not only the platelet count but also VTE presentation and the presence of cerebral metastasis.

HIGH-2-LOW risk model to predict venous thromboembolism in allogeneic transplant patients after platelet engraftment

Venous thromboembolism (VTE) after allogeneic hematopoietic cell transplantation (HCT) is a significant treatment-associated complication, although optimal timing of thromboprophylaxis remains uncertain when weighing concurrent risks of bleeding. We aimed to derive and internally validate a risk assessment model (RAM) using patients who underwent first allogeneic HCT from 2006 through 2015 (n = 1703). Index date was defined as the 30th day after transplant, at which point we estimated >75% of patients would have achieved platelet engraftment >50 × 109/L. Stepwise logistic regression modeling was used for model development, and internal validation was achieved by fitting a logistic regression model with 1000 bootstrapped resamples to estimate the optimism-corrected c-statistic. The final RAM, "HIGH-2-LOW," included 7 predictors obtained at 30 days after transplant: History of catheter-related deep venous thrombosis (DVT), Inpatient at day 30, Graft-versus-host disease grade 3 to 4, History of pulmonary embolism or lower-extremity DVT, Lymphoma diagnosis, Obesity with body mass index ≥35 kg/m2, and White blood cell count ≥11 × 109/L. Approximately 16% of patients were stratified as high risk, with incident VTE rate of 10.3% at 100 days compared with 1.5% for those at low risk. VTE odds ratios at 100 days were 5.87 (95% confidence interval [CI], 2.98-11.57) and 2.71 (95% CI, 1.38-5.35) in the high- and intermediate-risk vs low-risk groups, respectively. HIGH-2-LOW model serves as a novel and potentially clinically meaningful tool to identify high-risk allogeneic HCT patients who may benefit from early thromboprophylaxis after platelet engraftment.

Outcomes with enoxaparin dose reductions during thrombocytopenia in patients with hematopoietic stem cell transplantation (HSCT)

Introduction

Appropriate dosing of therapeutic anticoagulation during periods of thrombocytopenia remains uncertain for patients undergoing hematopoietic stem cell transplants (HSCT). There is a paucity of literature on treatment outcomes for HSCT patients treated with non-prophylactic, but reduced doses of therapeutic anticoagulation during thrombocytopenia. The primary objective was to determine the incidence of major bleeding events during thrombocytopenia when reduced-dose enoxaparin was administered.

Methods

This is a retrospective review of patients with a venous thromboembolic event (VTE) who underwent HSCT and received reduced-dose enoxaparin during thrombocytopenia at the Massachusetts General Hospital (MGH) from April 1, 2016 to August 31, 2018. Incidence of recurrent VTE and bleeding events for up to one month were investigated. Rates of recurrent VTE and enoxaparin dose adjustments (0.5 mg/kg twice daily vs 1 mg/kg daily) were also reviewed.

Results

Out of 172 patients reviewed, 27 patients met inclusion criteria. There were no recurrent VTEs within one month of initial enoxaparin dose reduction. There was one major bleeding episode that occurred while a patient was on full-dose enoxaparin; believed to be related to cyclophosphamide cardiopulmonary toxicity and resulted in death. There were six non-major bleeding episodes, only one of which was clinically significant and resulted in the discontinuation of enoxaparin.

Conclusion

Our evaluation of therapeutic enoxaparin dose reductions for thrombocytopenia in the HSCT patient population found this practice to be effective in reducing the recurrence of VTE with no major bleeding adverse events. However, the rate of non-significant minor bleeds should be monitored while on reduced-dose enoxaparin.

Platelet cut-off for anticoagulant therapy in thrombocytopenic patients with blood cancer and venous thromboembolism: an expert consensus

BACKGROUND

Management of venous thromboembolism (VTE) in patients with haematologic malignancies and thrombocytopenia is clinically challenging due to the related risks. No prospective studies or clinical trials have been carried out and, therefore, no solid evidence on this compelling issue is available.

METHODS

Given this, an expert panel endorsed by the Gruppo Italiano Malattie Ematologiche dell'Adulto Working Party on Thrombosis and Haemostasis was set up to produce a formal consensus, according to the RAND method, in order to issue clinical recommendations about the platelet (PLT) cut-off for safe administration of low molecular weight heparin (LMWH) in thrombocytopenic (PLT <100×109/L) adult patients with haematologic malignancies affected by acute (<1 month) or non-acute VTE.

RESULTS

In acute VTE, the panel suggests safe anticoagulation with LMWH at therapeutic doses for PLT between ≥50<100×109/L and at 50% dose reduction for PLT ≥30<50×109/L. In acute VTE for PLT <30×109/L, the following interventions are recommended: positioning of an inferior vena cava (IVC) filter with prophylactic LMWH administration and platelet transfusion. In non-acute VTE, anticoagulation with LMWH at therapeutic doses for PLT between ≥50<100×109/L or over and at 50% dose reduction for PLT ≥30<50×109/L is considered appropriate. The discontinuation of full or reduced therapeutic dose of LMWH is recommended for PLT <30×109/L, both in acute and non-acute VTE.

DISCUSSION

We suggest using dose-adjusted LMWH according to PLT to optimise anticoagulant treatment in patients at high bleeding risk.

Suboptimal use of pharmacological venous thromboembolism prophylaxis in cirrhotic patients

BACKGROUND

Cirrhosis was previously perceived as a haemorrhagic disease state due to frequent associations with coagulopathy and bleeding. However, the coagulopathy of cirrhosis is complex with defects in both procoagulant and anticoagulant factors. Derangements in common laboratory indices of coagulation do not accurately reflect bleeding risk or protection from thrombotic events.

AIMS

To assess the rate of pharmacological prophylaxis for venous thromboembolism (VTE) among hospital inpatients with cirrhosis and analyse factors associated with prophylaxis being inappropriately withheld.

METHODS

A retrospective cohort study was performed in a tertiary teaching hospital. Patients included were admitted for greater than 48 h with discharge diagnosis codes corresponding to chronic liver disease and/or cirrhosis. The use of VTE chemoprophylaxis with enoxaparin was assessed in cirrhotic patients and non-cirrhotic controls. Patient data collected included contraindications to prophylaxis, known high-risk varices, international normalised ratio (INR), creatinine, bilirubin, haemoglobin and platelet count.

RESULTS

Of 108 patients with cirrhosis eligible for VTE prophylaxis, 61 (56.5%) received prophylaxis compared to 104 (96.3%) non-cirrhotic patients. Platelets and INR were significantly different between those who did and did not receive VTE prophylaxis. On multivariate analysis, platelet count and INR were independent predictors for VTE not being administered.

CONCLUSION

The administration of chemoprophylaxis in accordance with the hospital guidelines was suboptimal in patients with cirrhosis. Platelet count and INR were independent predictors of prophylaxis use. Our results suggest persistent misperceptions that prolonged INR and thrombocytopenia predict bleeding risk in cirrhosis.

Management of anticoagulation for cancer-associated thrombosis in patients with thrombocytopenia: A systematic review

BACKGROUND

The management of anticoagulation for cancer-associated thrombosis (CAT) in patients with thrombocytopenia is controversial. Whereas some studies suggest that administration of reduced-dose low-molecular-weight heparin (LMWH) or temporary discontinuation for moderate and severe thrombocytopenia may be a safe and effective, others suggest full-dose anticoagulation with transfusion support. We sought to address this important knowledge gap and summarize the literature comparing these two common management strategies.

METHODS

A systematic review of the literature (PROSPERO CRD42017077127) using MEDLINE (inception to September 2017) was conducted. We included studies that reported recurrent venous thromboembolism (VTE) and major bleeding complications among patients treated with both of the two most common management strategies: therapeutic anticoagulation with platelet transfusion support and dose-modified anticoagulation for periods when the platelet count is <50 × 109/L.

RESULTS

A total of 134 article records were identified on the initial search and 10 articles underwent full text review. Two observational studies met the inclusions criteria. A total of 121 patients with CAT and thrombocytopenia were included. Forty-two of these patients had pulmonary embolism and 87 had deep vein thrombosis (DVT) including 38 upper extremity DVT. Overall, 27% of patients, regardless of their treatment strategy, experienced recurrent VTE. Thirteen percent of anticoagulated patients (15% of all patients) experienced a major bleeding episode. Meta-analysis could not be conducted.

CONCLUSIONS

Our findings do not support one management strategy over another to treat CAT patients with thrombocytopenia. However, the data highlights the heightened risk of recurrent VTE in this patient population despite the thrombocytopenia.

Venous thromboembolism incidence in hematologic malignancies

Venous thromboembolism (VTE) remains a major cause of morbidity and mortality in patients with cancer. Although some very well validated scores delineate the risk of VTE by cancer subtype and other risk factors, hematologic malignancies are underrepresented in these models. This subgroup represents a unique entity that undergoes therapy that can be thrombogenic. The overall risk of VTE in patients with leukemia depends on the use of L-asparaginase treatment, older age, comorbidities and central venous catheters. Patients with acute promyelocytic leukemia are at particularly high risk of VTE but also have an increased risk of bleeding. Patients with aggressive lymphomas have a high incidence of VTE, roughly 10%. Patients with multiple myeloma at highest risk of VTE are those receiving immunomodulatory agents such as thalidomide or lenalidomide. Allogeneic stem cell transplantation carries a risk of thrombosis, particularly in patients developing graft versus host disease. This review summarizes the incidence of VTE in leukemia, lymphoma, myeloma and stem cell transplantation and provides practical guidance for preventing and managing VTE in patients with hematologic malignancies.

Management of venous thromboembolism during thrombocytopenia after autologous hematopoietic cell transplantation

Management of venous thromboembolism (VTE) remains challenging in patients with hematologic malignancy who undergo hematopoietic cell transplantation (HCT) due to prolonged thrombocytopenia. This study aims to (1) determine the incidence of VTE recurrence and bleeding during autologous HCT, (2) assess the impact of continuing vs temporarily withholding anticoagulation during thrombocytopenia, and (3) explore the impact of platelet threshold among other variables on the risk of bleeding. We performed this observational study in adults with lymphoma and myeloma who underwent autologous HCT between 2006 and 2015. We selected patients with index VTE prior to HCT and assigned them to different cohorts based on antithrombotic management at the onset of thrombocytopenia. Primary outcomes included VTE recurrence and major bleeding by 30 days after HCT. Secondary outcomes included platelet and red blood cell transfusions, time to engraftment, and overall survival. Of the 1631 patients who underwent autologous HCT, 204 patients (12.5%) had preceding index VTE events, and among them, 132 patients continued and 72 patients temporarily withheld anticoagulation during thrombocytopenia. There were no significant differences in VTE recurrence (1.5% vs 1.4%) or major bleeding (3.8% vs 4.2%) between 2 groups by 30 days. The number of platelet transfusions was significantly higher in the first group. Baseline elevated bilirubin, creatinine, and prothrombin time were independently associated with increased risk in major bleeding, whereas neither platelet threshold nor average platelet count was predictive. Our findings suggest that for many patients undergoing autologous HCT, temporarily withholding anticoagulation during thrombocytopenia may offer the best risk-benefit tradeoff among available options.

Enoxaparin dose reduction for thrombocytopenia in patients with cancer: a quality assessment study

The development of thrombocytopenia in the setting of therapeutic anticoagulation for venous thromboembolic disease (VTE) is common in cancer patients, but guidelines for management are based on limited past data and have not been validated. In 2011, Memorial Sloan Kettering Cancer Center (MSKCC) implemented the following guidelines in this setting: administer full dose enoxaparin for a platelet count > 50,000/mcL, half-dose enoxaparin for a platelet count of 25,000-50,000/mcL, and hold anticoagulation for a platelet count < 25,000/mcL. We now report validation of safety and efficacy of these guidelines. As a Quality Assessment Initiative, we evaluated our guidelines for adult cancer patients at MSKCC who were on therapeutic-dose enoxaparin for VTE during the years 2011 through 2013 and experienced at least one 7-day period of thrombocytopenia (platelet count ≤ 50,000/mcL). We assessed adherence to the enoxaparin dose modification guidelines, major bleeding, clinically relevant non-major bleeding, recurrent VTE, and mortality during the thrombocytopenic episodes. We identified 99 patients with 140 episodes of thrombocytopenia of 7 or more days. The median duration of these thrombocytopenic episodes was 12 days. The enoxaparin dose was modified in 133 of the 140 episodes (95%), reflecting satisfactory adherence to our institutional guidelines. There were no recurrent VTE events or major bleeding episodes when the anticoagulant dose was reduced or held. In this cohort, there was only one major bleeding episode, a trauma-associated retroperitoneal hemorrhage that occurred on the third day of a thrombocytopenic episode, prior to enoxaparin dose modification. There were 13 clinically relevant non-major bleeding episodes. Lastly, 10 patients died of cancer-related causes during an episode of thrombocytopenia. This Quality Assessment Initiative supports the safety and efficacy of our guidelines for therapeutic enoxaparin dose modification.

Analysis of anticoagulation strategies for venous thromboembolism during severe thrombocytopenia in patients with hematologic malignancies: a retrospective cohort

The safety and efficacy of anticoagulation for venous thromboembolism (VTE) at times of severe thrombocytopenia is unclear. In this retrospective study, we evaluated patients with hematologic malignancy and either (1) acute or chronic VTE on anticoagulation before platelet count dropped below 50 × 10⁹/L or (2) acute VTE occurring while platelets were <50 × 10⁹/L. In 78 eligible patients, the primary outcomes of time to recurrent VTE or clinically significant bleeding within 100 d were compared by management strategy. Bleeding occurred in 27% of patients receiving anticoagulation versus 3% when anticoagulation was held (IRR 10.1, 95% CI 1.5-432.6). Recurrent VTE occurred in 2% of patients receiving anticoagulation versus 15% when anticoagulation was held (IRR 0.17, 95% CI 0.0-1.51). Most bleeding occurred before day 31(11/13), but recurrent VTE mostly occurred after day 40 (5/6). Our findings suggest that temporarily withholding anticoagulation for VTE during severe thrombocytopenia in patients with hematologic malignancies might reduce adverse outcomes.

Venous thromboembolism in patients with hematologic malignancy and thrombocytopenia

The optimal management of hematologic malignancy-associated venous thromboembolism (VTE) in patients with moderate-to-severe thrombocytopenia is unclear. This is a retrospective study of 128 adult patients with hematologic malignancies who were diagnosed with VTE. The outcome of patients with significant thrombocytopenia (≤50,000/µL) was compared with those without. Forty-seven patients (36.7%) had a platelet count ≤50,000/µL during a period of time of perceived need for new or continued anticoagulation. The median nadir platelet count in those with significant thrombocytopenia was 10,000/µL (range 2,000-45,000/µL) versus 165,000/µL (50,000-429,000/µL) in those without (P < 0.001). The median duration of significant thrombocytopenia in the first group was 10 days (1-35 days). Therapy during the period of significant thrombocytopenia included prophylactic-dose low-molecular-weight heparin (LMWH) (47%), therapeutic-dose LMWH or heparin (30%), warfarin (2%), inferior vena cava filter (2%), and observation (17%). Patients without thrombocytopenia were managed with the standard of care therapy. At a median follow-up of more than 2 years, the risk of clinically significant bleeding (11% vs 6%, P = 0.22) including major bleeding (6% vs 2%) and clot progression or recurrence (21% vs 22%, P = 1.00) were similar in patients with or without significant thrombocytopenia. In a multivariate analysis, the risk of recurrence/progression (hazard ratio, HR 0.59, 95% CI 0.21-1.66, P = 0.31) and hemorrhage rate (HR 0.29, 95% CI 0.05-1.56, P = 0.15) did not differ based on the presence of significant thrombocytopenia. Within the limits of this retrospective study, cautious use of prophylactic-dose LMWH may be safe in thrombocytopenic patients with hematologic malignancy-associated VTE. Am. J. Hematol. 91:E468-E472, 2016. © 2016 Wiley Periodicals, Inc.

Pathophysiology and management of thrombosis in cancer: 150 years of progress

The association of thrombosis with cancer has been recognized since the middle of the nineteenth century. It remains a common and serious complication of the cancer itself, as well as chemotherapy. Thrombosis is the second leading cause of death in cancer patients, second only to the cancer itself. For many years the treatment options for managing thrombosis in cancer had been static, but the past decade has seen significant evolution in the management, with the clear superiority of low molecular weight heparin over warfarin for secondary prevention of thrombosis. This article will review the understanding and management of thrombosis in cancer.

Between Scylla and Charybdis: antithrombotic therapy in hematopoietic progenitor cell transplant patients

Patients who undergo hematopoietic progenitor cell transplant may require antithrombotic therapy for a variety of reasons--history of vascular events or developing new ones during therapy. For patients with arterial disease, use of antiplatelet therapy is based on acuity. For primary prevention of an arterial event, aspirin can be withheld at the start of transplant. On the other hand, in the face of a patient experiencing an acute myocardial infarction, aspirin should be given, no matter what the degree of thrombocytopenia is. Patients with cardiac 'hardware'-stents and mechanical valves-pose difficult issues because as higher risk patients (especially patients with recent implantation of a drug eluting stent) they require more aggressive anticoagulation, even in the face of severe thrombocytopenia. Anticoagulation with heparin is dependent on the platelet count with full dose recommended for a platelet count over 50 × 10(9)/L and prophylactic dosing with platelets in the 20-50 × 10(9)/L range. If the patient develops a distal venous thrombosis, then simple observation can be used, but more proximal thrombosis or pulmonary embolism requires consideration of anticoagulation. Central venous catheter thrombosis is best treated by line removal, as the risk of bleeding is high if the device is left in. The advent of new anticoagulants with minimal drug and food interactions may offer better choices for therapy for these difficult patients. This is also an area in which clinical trials would be helpful to clarify the treatment choices.

Thrombosis in multiple myeloma

Patients with multiple myeloma (MM) are at an increased risk of venous and arterial thrombosis. The pathogenesis remains unclear, but probably involves several factors such as activation of procoagulant factors, acquired activated protein C resistance, and inflammation. In addition to general risk factors for venous thromboembolism, such as older age, immobility, surgery, and inherited thrombophilia, there are some MM-specific and treatment-related factors that contribute to the increased risk. The risk for venous thromboembolism is high when patients are treated with thalidomide or lenalidomide in combination with dexamethasone or multi-agent chemotherapy. Thromboprophylaxis should be given in these settings. Which agent is the most appropriate is a matter of debate, but aspirin, low-molecular-weight heparin, and warfarin all seem to be effective. This review discusses risk factors for thromboembolism in MM and general, disease-specific and treatment-related mechanisms for thrombosis. Recommendations for thromboprophylaxis are described and treatment choices for venous thrombosis in MM patients are reviewed.

Thrombotic Complications of Myeloma Therapy

Patients with multiple myeloma are at relatively high baseline risk of developing thromboembolic events (TEE), usually deep vein thromboses. There are numerous contributing factors, among them certain treatment regimens that include thalidomide or related compounds such as lenalidomide combined with glucocorticoids and/or cytotoxic chemotherapy. The risk of developing TEE appears to be particularly high when these immunomodulatory agents are combined with anthracyclines as treatment of newly-diagnosed disease. Up-front combinations including thalidomide plus pulse dexamethasone and/or alkylating agents are associated with an intermediate risk, whereas the same regimens for relapsed/refractory myeloma seem to be associated with the lowest risk. Several different thromboprophylaxis strategies have been effective in lowering the risk of developing clots: daily aspirin (81–325 mg/day), full-intensity warfarin (INR 2–3), and prophylactic enoxaparin (40 mg SQ daily). Low, fixed-dose warfarin may also reduce the risk of TEE, but the data on this are disputable. None of these TEE prevention strategies have been prospectively compared head-to-head, so the choice often reflects physician and/or patient preferences. The available evidence upon which one might make such a decision is reviewed here.