Cancer-Associated Thrombosis

Patient Experience

  • Reference Number: HEY-995/2018
  • Departments: Haematology, Oncology (Cancer Services)
  • Last Updated: 10 July 2018


This leaflet has been produced to give you general information about blood clots and cancer, what to look out for and how to avoid them.  Most of your questions should be answered by this leaflet. It is not intended to replace the discussion between you and your doctor, but may act as a starting point for discussion. If after reading it you have any concerns or require further explanation, please discuss this with a member of the healthcare team caring for you.

What is cancer-associated thrombosis?

Cancer – Associated Thrombosis, commonly known as CAT, is the development of blood clots inside a blood vessel and is associated with cancer.

Cancer – Associated Thrombosis’ are blood clots that can commonly occur within the deep vein of a limb, known as deep vein thrombosis (DVT) and the lungs, known as pulmonary embolism (PE) but can also occur elsewhere in the venous (blood) system.

CAT is not caused by anything you have or have not done. Some people are more likely to develop blood clots than others.

The diagnosis of cancer and its treatments (e.g. chemotherapy) are well-recognised risk factors for the formation of blood clots. Other risks include being inactive and/or having surgery or having a central venous access device in place. Certain types of cancer are also more likely to be associated with CAT.

Can there be any complications?

There are 1 in 5 people with cancer who will develop a blood clot.  As with all blood clots, CAT can be serious and is a significant cause of death in cancer patients.  However, there are effective medicines which can treat or prevent further blood clots forming.

How can I avoid CAT?

You can help to reduce your risk of developing CAT by:

  • Exercising little and often as this will help to keep the blood flowing.
  • Changing your position and moving your legs regularly, particularly if you are sitting or lying down for long periods of time.
  • Unless you have been told to restrict your fluid intake, drink plenty of fluids but avoid coffee and alcohol where possible.
  • Stopping smoking. Your healthcare team can help and support you with this should you require more information.

What are the signs of blood clots?

It is important to be aware of the potential signs of blood clots.

Signs you may have developed a blood clot in the leg (DVT) include:

  • Tenderness in the leg
  • Redness
  • Swelling and a feeling of tightness, the skin may feel stretched
  • Pain in the leg (usually the calf)
  • Warmth and redness of the skin (particularly at the back of the leg, below the knee)

Or for a blood clot in the lungs (or PE) include:

  • Light-headedness or feeling faint
  • Unexplained shortness of breath
  • Chest pain, particularly when you take a deep breath
  • Coughing up blood
  • Sweating

What is the treatment for CAT?

If you do develop a blood clot whilst being treated for cancer there is an effective treatment which will help manage your CAT and prevent further blood clots from forming.

The recommended treatment for CAT is an injected type of anticoagulant, or blood thinner, called low-molecular weight heparin (LMWH) which is given every day for 6 months. In some cases the treatment may have to be extended beyond the 6 months; however this will be a discussion you will have with your GP or consultant.

Although these blood thinners are generally safe medications they do increase the chances of bleeding.  If you experience any of the following, seek medical attention.

  • Prolonged nosebleeds (more than 10 minutes)
  • Blood in vomit
  • Coughing up blood
  • Passing blood in your urine or faeces
  • Passing black stool
  • Severe or spontaneous bruising
  • Unusual headaches
  • For women, heavy or increased bleeding during your period or any other vaginal bleeding

If you cut yourself, apply firm pressure to the site for at least five minutes using a clean, dry dressing.

Seek immediate medical attention if you:

  • Are involved in an accident
  • Suffer a significant blow to the head
  • Are unable to stop bleeding

What happens afterwards?

You will be shown how to give the injections yourself at home. Alternatively, a district nurse can come to your home to give you the injection.

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

Useful Contact numbers:

Should you require further advice about the issues contained in this leaflet, please do not hesitate to contact the

Chemotherapy Nurse Specialist Team (01482) 461098 During the hours of 8:00am – 6:00pm

Outside of these hours please contact the main hospital switchboard on (01482) 875875 and ask to speak to bleep 500

If you suddenly become unwell and breathless please attend the Emergency Department or dial 999 for an ambulance.

General Advice and Consent

Most of your questions should have been answered by this leaflet, but remember that this is only a starting point for discussion with the healthcare team.

Consent to treatment

Before any doctor, nurse or therapist examines or treats you, they must seek your consent or permission. In order to make a decision, you need to have information from health professionals about the treatment or investigation which is being offered to you. You should always ask them more questions if you do not understand or if you want more information.

The information you receive should be about your condition, the alternatives available to you, and whether it carries risks as well as the benefits. What is important is that your consent is genuine or valid. That means:

  • you must be able to give your consent
  • you must be given enough information to enable you to make a decision
  • you must be acting under your own free will and not under the strong influence of another person

Information about you

We collect and use your information to provide you with care and treatment. As part of your care, information about you will be shared between members of a healthcare team, some of whom you may not meet. Your information may also be used to help train staff, to check the quality of our care, to manage and plan the health service, and to help with research. Wherever possible we use anonymous data.

We may pass on relevant information to other health organisations that provide you with care. All information is treated as strictly confidential and is not given to anyone who does not need it. If you have any concerns please ask your doctor, or the person caring for you.

Under the General Data Protection Regulation and the Data Protection Act 2018 we are responsible for maintaining the confidentiality of any information we hold about you. For further information visit the following page: Confidential Information about You.

If you or your carer needs information about your health and wellbeing and about your care and treatment in a different format, such as large print, braille or audio, due to disability, impairment or sensory loss, please advise a member of staff and this can be arranged.

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