A Feasibility Study to Inform the Design of a Randomised Controlled Trial to Identify the Most Clinically and Cost Effective Length of Anticoagulation With Low Molecular Weight Heparin In the Treatment of Cancer Associated Thrombosis

Venous thromboembolism (VTE) is a term to describe blood clots in the legs known as a deep vein thrombus (DVT) or lung, known as a pulmonary embolus (PE). It is a common condition, which causes many symptoms including leg pain, swelling, chest pain and breathlessness. At its most serious, VTE may lead to sudden collapse and death.

Treating VTE costs the UK National Health Service (NHS) £640 million every year, including the long-term complications experienced by nearly a third of patients. VTE treatment usually consists of three to six months blood thinning medicine known as an anticoagulant. For most patients, a tablet called warfarin is used, which requires regular blood tests to ensure the blood is adequately and safely thinned.

We also know that VTE is particularly common in cancer. In the UK, over 250,000 people are diagnosed each year with cancer, of which nearly a fifth will develop VTE. Warfarin is a potentially risky treatment in cancer patients because it may increase the risk of bleeding. Also, VTE may come back in a fifth of patients who are treated with warfarin.

Research has shown that a medicine known as low molecular weight heparin (LMWH) is better than warfarin at treating VTE in cancer patients and decreases the chance of VTE coming back by half. LMWH is given as an injection once a day. Studies have shown that giving the drug as an injection is acceptable to patients, as some patients prefer this to the regular blood tests they need to have for warfarin monitoring. LMWH is also simpler to use since it does not cause problems for patients taking other medicines which is a common problem for patients taking warfarin.

Cancer patients get VTE because the cancer can make the blood sticky and this makes it more likely to clot. It is recommended that patients take LMWH for six months only. However, if someone still has a cancer after six months of treatment with LMWH, there is still a strong chance that the VTE could come back because the cancer causing the blood clots has not gone away. This means that these patients might benefit from taking LMWH for longer than six months. We do not know though whether this would improve the patients' quality of life, help prevent death, or be cost-effective to the NHS.