Comparing the Efficacy of Aspirin or Low Molecular Weight Heparin or Vitamin K Antagonists in the Risk of Thromboembolic Events in Patients with Multiple Myeloma Treated with Lenalidomide-Based Therapy

Background

Malignancy is a well-recognized risk factor for venous thromboembolism (VTE). In multiple myeloma the incidence of VTE varies between 3% and 10%.  Immunomodulatory drugs (IMiDs) play a crucial role in the treatment of myeloma and are known to be associated with an increased risk of arterial and venous thromboembolic events (TE). It appears that patients with newly diagnosed multiple myeloma (NDMM) are at higher risk for TE compared to patients with relapsed or refractory myeloma (RRMM) at the start of IMiD therapy.

Lenalidomide is a second-generation IMiD which in combination to dexamethasone has shown to be an effective and well-tolerated therapy for patients with NDMM or RRMM. However, studies have consistently demonstrated the need for TE prophylaxis in patients receiving the combination lenalidomide-dexamethasone which leads to a 4.4-fold increased risk for VTE compared to dexamethasone alone in the absence of prophylactic anticoagulants. 

Panel consensus from the International Myeloma Work Group has agreed that the choice of thromboprophylaxis depends on the individual risk of TE, as determined by patient and treatment-related factors, such as obesity, prior VTE, central venous catheter, immobilization, recent surgery, comorbidities, use of erythropoietin stimulating agents and myeloma therapy.  Aspirin (ASA) is recommended for patients with one or no risk factors, and LMWH for those with more than one risk factor. However, the optimal approach to thromboprophylaxis has not yet been established.

In this study we sought to compare the efficacy of ASA or low molecular weight heparin (LMWH) or vitamin K Antagonists (VKA) in the prevention of VTE or arterial thromboembolism (ATE) in patients with myeloma using lenalidomide- based therapy.

Methods

 We performed a retrospective chart review in 2 centres (London, Canada ; and Salamanca, Spain) on patients with NDMM or RRMM multiple myeloma receiving lenalidomide-based therapy. We collected data from january 2010 to December2014.

We included adult patients diagnosed with NDMM or RRMM  receiving lenalidomide-based therapy. We did not include  who received lenalidomide but refused or had contra-indication to thromboprophylaxis; or  used single agent lenalidomide.

Results

We included 168 patients with multiple myeloma receiving lenalidomide-based therapy. 14 (8%) were NDMM and 154 (92%) had RRMM. Median age was 68 (31-89) and 106 (63%) were males.  On average patients with RRMM had 1.6 previous treatments (range:1-11). 104 (62%) patients were low risk and 64 (38%) were high risk for TE.  140 (83%) patients received prophylaxis with ASA , 32 (19%) LMWH and 6 (4%) VKA. 10 patients started with prophylactic  LMWH for an average of 2 months then were empirically switched over to ASA. In total, there were 18 (10.7%) TE of which, 16 (9.5%) were VTE: 3 PE, 12 DVT, 1 both.     The relative risk for TE was the same regardless of risk stratification [RR=1.27 (95%CI 0.524 – 3.059; p=0.599)]. At TE diagnosis, 16 patients were on ASA, 1 on LMWH and 1 on VKA. The relative risk of TE was significantly higher for patients on ASA compared to LMWH or VKA [RR= 2.17 (0.522 – 9.03;p= 0.286).

After the TE, all patients changed anticoagulation strategy: 15 of 16 (94%) patients with VTE switched to therapeutic LMWH and 1 who was on VKA had ASA added. In the 2 patients with ATE, 1 started on full dose LMWH and the other one continued on ASA.  16 of 18 patients with a TE continued on lenalidomide-based therapy. There was no recurrent arterial or venous TE within the first 6 months of anticoagulation after the  TE. Univariate analysis suggested that BMI, use of ASA and sex could be potential predictors of TE; but the logistic regression was not statistically significant (Table).

 Conclusions

In patients with multiple myeloma on lenalidomide-based therapy the preferred TE  prophylactic approach is low dose ASA irrespective of patients' risk assessment  for thromboembolism. However, VTE risk in these patients is not negligible (9.5%) and low dose ASA may not  be the best prophylactic strategy for them.  It appears that patients on ASA, obese and males are at higher risk for TE. Future studies are needed to confirm these assumpations.

Table 1- Multivariate Analysis of the TE risk for patients with myeloma on lenalidomide-based therapy

Odds Ratio
Variable	Point Estimate	95% CI		p-value
Sex	2.316	0.854	6.278	0.0989
BMI	1.705	0.501	5.804	0.3935
ASA	3.870	0.486	30.796	0.2010