The effects of low molecular weight heparins on venous thromboembolism and survival in patients with cancer.

Monotherapy with low molecular weight heparin (LMWH) is superior to vitamin K antagonists in preventing recurrent venous thromboembolism (VTE) in patients with cancer and may improve the survival of patients with less advanced malignancies. These agents are also the preferred anticoagulants for primary prophylaxis in medical and surgical patients in hospital. Despite their limitations, LMWHs have improved the quality of care and quality of life in patients with VTE. Recent research has also explored the role of LMWH as anticancer agents. Evidence from experimental studies have demonstrated inhibitory effects of LMWH on various processes that are necessary for tumour growth and progression while results from clinical trials have shown a reduction in overall mortality in patients treated with LMWH. However, because of limitations and differences in study designs as well as small sample sizes, it remains uncertain whether the reduction in mortality is real and whether LMWH achieve this effect through inhibition of coagulation, non-anticoagulant mechanisms or both. Multiple anticancer mechanisms, including inhibition of tumour angiogenesis, interference with tumour cell adhesion, and suppression of tumour cell invasion, have been demonstrated in experimental models with LMWH, but none have been confirmed in vivo in humans. This review will briefly summarize the data on the treatment of VTE in cancer patients with LMWH and discuss the experimental and clinical data on its possible anticancer effects.