Results Summary

What was the research about?

People with cancer have a higher-than-normal risk for blood clots. These blood clots form in the veins, and they can cause pain and lead to hospital stays or even death.

Blood thinners can prevent clots but may cause problems such as severe bleeding. Also, most patients who use older blood thinners must inject them each day using needles; they may also need frequent blood tests. Since 2012, patients can take newer blood thinner pills by mouth. These medicines do not require regular blood tests.

In this study, the research team wanted to learn whether the newer pills were worse or no worse than the injectable blood thinners at preventing future blood clots among patients with cancer who had a recent clot.

What were the results?

After six months, the two types of blood thinners worked about the same to prevent clots. However, about 71 percent of patients taking the newer blood thinners kept taking their assigned medicine compared with 59 percent of patients on the older injectable blood thinners.

Patients taking newer blood thinners and patients taking older blood thinners didn’t differ in:

  • Cases of bleeding
  • Serious side effects
  • Quality of life
  • Reported burden and benefits of taking the medicine
  • Deaths

Who was in the study?

The study included 638 adults with cancer who had a blood clot within the last month. All were receiving care at one of 67 cancer clinics across the United States. Among patients, 83 percent were White, 11 percent were Black or African American, and 5 percent were another, more than one, or unknown race; 5 percent were Hispanic. The average age was 61, and 55 percent were women.

What did the research team do?

The research team assigned patients by chance to receive either the newer or older blood thinners. The patients’ doctors could choose which type of newer or older blood thinner patients received. During the study, patients who took the older injectable blood thinners could switch to warfarin, a blood thinner taken by mouth, if they had difficulty with the injections. Patients in both groups saw their doctors as needed for care.

At the start of the study and again after six months, patients completed surveys. Surveys asked if patients were taking their medicine and about quality of life as well as the burden, benefits, and side effects of medicines. The research team also reviewed patients’ health records for other health outcomes.

Patients with cancer, patient advocates, and doctors gave input on the study design.

What were the limits of the study?

The research team didn’t recruit as many patients into the study as they had planned. Therefore, the team could not tell if one type of blood thinner was better than the other, only if one type was no worse than the other.

Future research could determine which type of blood thinner is better for preventing blood clots among patients with cancer.

How can people use the results?

Patients with cancer and their doctors can use these results when considering medicines to prevent blood clots.

Final Research Report

View this project's final research report.

Peer-Review Summary

Peer review of PCORI-funded research helps make sure the report presents complete, balanced, and useful information about the research. It also assesses how the project addressed PCORI’s Methodology Standards. During peer review, experts read a draft report of the research and provide comments about the report. These experts may include a scientist focused on the research topic, a specialist in research methods, a patient or caregiver, and a healthcare professional. These reviewers cannot have conflicts of interest with the study.

The peer reviewers point out where the draft report may need revision. For example, they may suggest ways to improve descriptions of the conduct of the study or to clarify the connection between results and conclusions. Sometimes, awardees revise their draft reports twice or more to address all of the reviewers’ comments. 

Peer reviewers commented and the researchers made changes or provided responses. Those comments and responses included the following:

  • The reviewers asked why the researchers chose to close the preference cohort in which study participants had the opportunity to choose their treatment rather than be randomized. The researchers explained that they developed closing rules for the preference cohort so that entry would be closed if a large imbalance developed in participants’ choice of treatment. The researchers noted that a much larger proportion of participants in the preference cohort chose direct oral anticoagulants (DOACs) compared to those who chose usual care, creating an imbalance that could induce information loss in subsequent statistical analyses.
  • The reviewers suggested that the researchers delineate how this study was a pragmatic trial which differed from industry-sponsored clinical trials. The researchers did not directly compare traditional clinical trials to pragmatic trials, but in the background section they did list the advantages of the pragmatic trial design for their specific study question.
  • The reviewers noted that the report identified the primary study outcomes as recurrent venous thromboembolism (VTE) or VTE-related death within six months of treatment randomization despite the researchers acknowledging the difficulty of attributing cause of death because diagnostic procedures are rarely performed post-mortem on cancer patients with recurrent VTE. The researchers corrected the report to list only recurrent VTE based on antemortem diagnosis as a primary outcome, with all-cause mortality as secondary. 

Project Information

Deborah Schrag, MD, MPH
The Alliance for Clinical Trials in Oncology Foundation
Direct Oral Anticoagulants (DOACs) versus LMWH +/- Warfarin for VTE in Cancer: A Randomized Effectiveness Trial (CANVAS Trial)

Key Dates

September 2015
November 2022

Study Registration Information


Has Results
Award Type
Health Conditions Health Conditions These are the broad terms we use to categorize our funded research studies; specific diseases or conditions are included within the appropriate larger category. Note: not all of our funded projects focus on a single disease or condition; some touch on multiple diseases or conditions, research methods, or broader health system interventions. Such projects won’t be listed by a primary disease/condition and so won’t appear if you use this filter tool to find them. View Glossary
Intervention Strategy Intervention Strategies PCORI funds comparative clinical effectiveness research (CER) studies that compare two or more options or approaches to health care, or that compare different ways of delivering or receiving care. View Glossary
State State The state where the project originates, or where the primary institution or organization is located. View Glossary
Last updated: November 17, 2023