Reduction to Preventive Doses of Enoxaparin After 3 to 6 Months of Treatment With Blood Thinners for Cancer-associated Blood Clots

Background: Venous thromboembolism (VTE), which includes deep vein thrombosis (DVT) and pulmonary embolism (PE), is the third most common cardiovascular disorder after myocardial infarction and stroke. VTE occurs in about 1 person per 1,000 per year, increasing dramatically in patients with cancer to about 25 per 1,000 per year. Among the known risk factors of VTE, cancer is one of the most potent. Patients with cancer have a 7- to 28-fold higher risk for VTE than non-cancer patients. VTE has important implications for the care of cancer patients, including reduced life expectancy, high rates of VTE recurrence both while on and after stopping anticoagulation, the need for chronic anticoagulation with related adverse drug reactions, and delays in cancer therapies. Clinical dilemma: Current clinical guidelines recommend a minimum of 3-6 months of anticoagulation with weight-adjusted low molecular weight heparin (LMWH) in cancer patients with VTE. However, there are no recommendations beyond the initial 6 months of therapy due to the lack of data on extended duration therapy for cancer-associated thrombosis (CAT). This leads to variability in physician practices, with some continuing weight-adjusted LMWH therapy beyond 6 months. This poses concern because, while the goal is to prevent recurrence of VTE, the risk of major bleeding with prolonged weight-adjusted LMWH therapy is significant. Potential solutions: There is a lack of data to inform on VTE treatment in cancer patients beyond the initial 3-6 months of anticoagulation. We propose that after a minimum of 3-6 months of therapeutic dose anticoagulation, the use of prophylactic doses of LMWH will have an acceptable and adherence profile in cancer patients with VTE. The data obtained from this study will help inform physician practices. Design: This is a multicentre, open-label study of enoxaparin (40 mg subcutaneous injection, once daily) for additional 6 months after an initial minimum 3-6-month course of therapeutic dose anticoagulant therapy. Patients: 150 patients with VTE secondary to cancer will take part in this multicentre study conducted in 8 Canadian centres within Quebec, Ontario and Nova Scotia. Study Outcomes: The primary objective of the study is to determine the rate of recurrent VTE in patients receiving prophylactic dose enoxaparin for secondary VTE prophylaxis after an initial minimum 3-6 months of anticoagulation. The secondary objective is to determine the safety profile of prophylaxis dose enoxaparin for secondary VTE prophylaxis after an initial 3-6 months of anticoagulation. This includes determining for all subjects: 1) cumulative incidence of major bleeding events; 2) cumulative incidence of clinically relevant non-major bleeding events; 3) cumulative incidence of minor bleeding event, and 4) overall survival during follow-up.


Eligibility Criteria:
Inclusion Criteria:

* Have an active malignancy defined as any of: a) Diagnosis of cancer (excluding basal cell or squamous cell carcinoma of the skin) within 18 months of enrollment; b) Have received treatment for cancer within 18 months (e.g. radiation therapy, chemotherapy, adjuvant therapy); c) Have documented recurrent or metastatic cancer
* Receiving a 3-6 month course of weight-adjusted LMWH for an acute, objectively confirmed, symptomatic VTE (proximal or distal DVT of the lower extremity, proximal DVT of the upper extremity, or PE)
* Age ≥ 18 years
* Life expectancy \> 6 months
* Able to comply with scheduled follow up visits
* Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2
* Willing to provide written informed consent

Exclusion Criteria:

* Distal DVT of the upper extremity
* Recurrent VTE during the 3-6-month LMWH treatment period
* Major or clinically relevant non-major bleeding during the 3-6 month LMWH treatment period
* Risk of bleeding (e.g. recent neurosurgery, history of intracranial hemorrhage, acute gastroduodenal ulcer, etc.)
* Diagnosis of basal cell and squamous cell carcinoma of the skin or acute Leukemia
* Platelet count \< 50 x 109/L
* Creatinine clearance \<30ml/min (using the modified Cockcroft-Gault formula)
* On hemodialysis
* Known hypersensitivity to heparin, LMWHs, or pork products
* Known contraindication to the use of heparin (e.g. heparin-induced thrombocytopenia)
* Currently participating in another clinical trial involving anticoagulation therapy (with the exception of aspirin)
* Pregnancy or breastfeeding
* On an anticoagulant for a different indication
* Treating physician plans for weight-adjusted LMWH for longer than 3-6 months duration