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Cancer and blood clots reducing the risk

This information explains what deep vein thrombosis (DVT) and pulmonary embolism (PE) blood clots are and why people with cancer are at higher risk of developing these type of blood clots (called cancer associated thrombosis or CAT). It also explains how to reduce the risk of cancer associated thrombosis (CAT).

What are blood clots (VTE)?

Your blood has a mechanism that normally forms a blood clot (plug) to stop the bleeding when you are injured (example: when you have a cut). Sometimes this mechanism can go wrong and forms a blood clot without an injury, which can block the vein and stop the blood flowing to the affected area.

This is called venous thromboembolism (VTE), which can happen:

  • In a vein of the leg causing a deep vein thrombosis (DVT)
  • If the DVT becomes loose, it can travel to the lungs causing a pulmonary embolism (PE). This condition can be fatal.

DVT can lead to post-thrombotic syndrome on the leg (permanent pain, difficulty walking, leg wounds that don’t heal).

PE when not fatal, can lead to chronic pulmonary hypertension (weak heart, chest pains, shortness of breath).

Cancer Associated Thrombosis

People with cancer are at higher risk of developing blood clots compared to someone who does not have cancer. This is because:

Cancer cells release chemicals that increase blood clotting. If the cancer has spread that also increases the risk

Cancer treatments such as surgery and chemotherapy, damage the vein’s inner layer triggering blood clotting.

Being less active when you don’t feel well, leading to a slower blood flow, which makes it easier for blood clots to form.

Some types of cancer carry more risk of blood clots:

  • Lung cancer
  • Kidney cancer
  • Ovarian cancer
  • Brain cancer
  • Lymphoma
  • Pancreatic cancer

Some cancer treatments carry more risk of blood clots:

  • Any surgery
  • Chemotherapy particularly cisplatin
  • Hormone therapy such as tamoxifen and anastrozole
  • Immunomodulatory drugs such as thalidomide and lenalidomide
  • Antiangiogenic therapies such as bevacizumab and sunitunib
  • Supportive agents such as erythropoietin and darbopoetin

Other risk factors:

The risk of VTE varies between people as other risk factors come into play.

The more risk factors, higher is the risk:

  • Being over 60
  • Being overweight
  • Having another medical condition such as diabetes, asthma, high cholesterol or heart disease
  • Dehydration
  • Pregnancy or 6 weeks post birth
  • You or your family member having a blood clot in the past
  • Taking the contraceptive pill or HRT
  • Recent surgery, hospital admission, long journey (plane, car, train, bus)
  • A significant reduction in your mobility, spending long periods housebound, in bed or chair

Don’t worry

  • It is a good thing to know your risk so you can do something about it.
  • Having risk factors does not mean you will have VTE.
  • Not having risk factors also does not mean you will not have VTE.
  • There are lots of things you can do to reduce the VTE risk. 

How to reduce the risk?

General recommendations for all patients with cancer:

  • Stay Active
  • Drink Plenty
  • VTE Prevention Exercises
  • These exercises should be done at least 3 x a day

How do you know if you have VTE?

Unfortunately, if you follow all of the advice to prevent VTE, you may still get it, even if you are at low risk.

So keep an eye out for DVT and PE:

  • Swelling of the leg or calf
  • Pain that may worsen when standing or walking
  • Warmth and redness of the leg

If you suspect you have a DVT call your GP as soon as possible!

  • Unexplained sudden breathlessness
  • Sudden sharp chest
  • Coughing up blood

This is an emergency. If you suspect you have a PE call 999 immediately!

Useful information:

Buckinghamshire Hospitals Trust Patient Medicines Helpline: 01296 31 6197

National Institute for Health and Care Excellence: Venous thromboembolism in over 16s: reducing the risk of hospital-acquired deep vein thrombosis or pulmonary embolism

DVT (deep vein thrombosis) – NHS (

Download the App Preventing VTE (found in Google Play)