The effect of anticoagulants on cancer risk and survival: systematic review

Several in vitro and in vivo studies have shown that low molecular weight heparin and warfarin may directly inhibit tumour cell growth and prevent metastatic spread. However, the clinical evidence in support of an anti-cancer effect is less conclusive. We summarize the evidence from clinical studies that examine the effect of these anticoagulants on cancer development and briefly describe the current understanding of the potential mechanisms by which anticoagulants may exert an anti-cancer effect.

English-language articles reporting on warfarin, coumarin or low molecular weight heparin for the treatment or prevention of cancer were selected from PUBMED. All randomized clinical trials, case-control studies, cohort studies, and meta-analyses were retrieved. Detailed data review and abstraction was performed according to pre-specified criteria.

Of ninety-nine articles retrieved, 12 warfarin and 17 low molecular weight heparin articles were included in the review. We found no consistent evidence that warfarin may improve cancer survival, though there is indirect evidence that prolonged warfarin use may decrease the risk of urogenital cancer. Low molecular weight heparin may improve survival of patients with small cell lung cancer and those with advanced malignancy who have more favorable prognoses.

Clinical evidence exists in support of an anti-neoplastic effect of anticoagulants. However, more research is needed to further define which cancer type and stage would most benefit from low molecular weight heparin, as well as to explore the role of warfarin in urogenital tumour development.