Oral blood thinners in patients with cancer


This review assessed the effects of oral anticoagulation (blood-thinning drugs) in people with cancer on survival, thromboembolic events, and bleeding outcomes.

Study characteristics

We searched the scientific literature for studies of anticoagulants in people with cancer. The evidence is current to February 2013.

Key results

We found six studies using warfarin and one study using apixaban. When considering people with cancer in general, warfarin did not reduce mortality, but did reduce the risk of venous clots while increasing the risk of minor and major bleeding. Apixaban reduced DVT and had no effect on death, major bleeding, or minor bleeding; however, this was in only one study.

Quality of the evidence

We judged the evidence on warfarin to be moderate quality and the evidence of apixaban as low quality.

Authors' conclusions: 

Existing evidence does not suggest a mortality benefit from oral anticoagulation in patients with cancer while the risk for bleeding is increased.

Read the full abstract...

Several basic research and clinical studies have led to the hypothesis that oral anticoagulants may improve the survival of patients with cancer through an antitumor effect in addition to their antithrombotic effect.


To evaluate the efficacy and safety of oral anticoagulants in patients with cancer with no therapeutic or prophylactic indication for anticoagulation.

Search strategy: 

We performed a comprehensive search for studies of anticoagulation in patients with cancer including 1. a February 2013 electronic search of the following databases: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and EMBASE; 2. a handsearch of the American Society of Clinical Oncology (starting with its first volume, 1982) and of the American Society of Hematology (starting with the 2003 issue); 3. checking of references of included studies; 4. use of the 'related citation' feature in PubMed; and 5. searching clinical trials.gov for ongoing studies.

Selection criteria: 

Randomized controlled trials (RCTs) comparing vitamin K antagonist or other oral anticoagulants with no intervention or placebo in patients with cancer without clinical evidence of venous thromboembolism.

Data collection and analysis: 

Using a standardized data form, we extracted data on risk of bias, participants, interventions and outcomes of interest that included all-cause mortality, venous thromboembolism, major bleeding, and minor bleeding.

Main results: 

Of 9559 identified citations, seven RCTs (eight reports) fulfilled the inclusion criteria. The oral anticoagulant was warfarin in six of these RCTs and apixaban in the seventh RCT. The comparator was either placebo or no intervention. The use of warfarin had no effect on mortality at six months (risk ratio (RR) 0.98; 95% confidence interval (CI) 0.82 to 1.22), one year (RR 0.97; 95% CI 0.89 to 1.04), two years (RR 0.98; 95% CI 0.81 to 1.18), or five years (RR 0.92; 95% CI 0.83 to 1.01). One study assessed the effect of warfarin on venous thromboembolism and did not show or exclude a beneficial or detrimental of effect (RR 0.15; 95% CI 0.02 to 1.20). Warfarin increased both major bleeding (RR 4.24; 95% CI 1.86 to 9.65) and minor bleeding (RR 3.19; 95% CI 1.83 to 5.55). We judged the quality of evidence as moderate for all outcomes.

The study assessing the effect of apixaban did not show or exclude a beneficial effect or detrimental of apixaban on mortality at six months (RR 0.16; 95% CI 0.01 to 1.66); major bleeding (RR 0.62; 95% CI 0.06 to 6.63); and minor bleeding (RR 2.87; 95% CI 0.16 to 51.82). We judged the quality of evidence as low for all outcomes.