Anticoagulation UK

Cancer associated thrombosis (CAT)

If you are diagnosed with cancer, there will be a lot going through your mind, and blood clots probably aren't going to be the first thing you think about.

It is worth remembering that developing a blood clot while living with cancer is far from unusual - 1 in 5 people with cancer will develop a clot. Despite this, Cancer Associated Thrombosis (CAT) is not commonly discussed.

As with all blood clots, CAT is serious.

However, there are effective medicines that can treat, or prevent further blood clots from forming.

CAT is not your fault, it is not caused by anything you have done, some people are simply more likely to develop a clot than others.

There are a number of risk factors:

Being treated for cancer.

Being inactive (in hospital) and/or having surgery can also raise the risk of cancer-associated thrombosis.

While all cancers increase your risk of a clot particular types of cancer will raise your risk of developing a clot, specifically:

  • Colorectal
  • Lung
  • Ovarian
  • Stomach
  • Pancreatic

Your healthcare team should talk to you about clots and regularly review your risk throughout your treatment. If you aren’t sure if this has happened, you should ask.

Avoiding CAT

Fortunately, there are ways in which you can reduce your risk of CAT:

  • Exercising little and often - moving helps keep the blood flowing (This could include walking, golf or gardening)
  • Remember to change position and move your legs and feet regularly - particularly if you are sitting or lying down for a long period
  • Quitting smoking can also help to reduce your risk of clots. Your healthcare team can help and give you support should you want more information
  • Try to drink plenty of fluids but avoiding coffee or alcohol where possible

50% of Cancer Associated Blood Clots occur within the first three months of someone being diagnosed with cancer

Treatment for CAT

If you do develop a blood clot while being treated for cancer, there are effective treatments that can help manage your CAT and prevent further clots from forming.

Importantly, the treatment for CAT is different to that for deep vein thrombosis (DVT) or pulmonary embolism (PE). The recommended treatment for CAT is an injected type of anticoagulant called low-molecular weight heparin (LMWH), every day for 6 months.

It is important that you keep taking the treatment every day for at least 6 months, or for as long as your doctor advises.

If you are unclear on how to use your treatment, refer to the information inside the pack you received, known as the Patient Information Leaflet, or speak to your healthcare team.

If you are worried about clots, immediately contact your healthcare team. Check you have contact details for your healthcare team and write them down.

For more information on what signs to look for:

Watch the CAT video diary

If you are worried about clots, immediately contact your healthcare team. Check you have contact details for your healthcare team and write them on your CAT Alert Card.

To request a CAT Alert card please email with your name and address.

To order CAT Alert cards in bulk for your patients please email stating how many you would like and your name and address.

Blood clots pose a very significant risk to cancer patients.

Watch Teresa's story

Sara talks about her colon cancer and her cancer associated pulmonary embolism

Watch Sara's story