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Learn about blood clots and breast cancer, including what can increase your risk of a blood clot, how to reduce your risk and how blood clots are treated.

1. Breast cancer and blood clots

People with breast cancer have a higher risk of blood clots. Their risk is higher because of the cancer itself and some treatments for breast cancer.

If the cancer has spread to other parts of the body (), this can also increase the risk.

Blood clots can be harmful but are treatable, so it’s important to report symptoms as soon as possible. If you develop a blood clot during treatment, your treatment may be paused until the blood clot has been treated.

Blood clot symptoms

If you have any of the following symptoms, contact your treatment team or go to your local A&E department immediately:

  • Pain, redness/discolouration, heat and swelling of the arm or leg
  • Swelling, redness or tenderness where a central line is inserted to give chemotherapy - for example in the arm, chest area or up into the neck
  • Shortness of breath
  • Pain or tightness in the chest
  • Unexplained cough or coughing up blood

Find out more about blood clots.

2. Types of blood clot

Blood clots can naturally happen quite often. If you have an injury your blood will clot to reduce bleeding.

But there are times when blood clots can be harmful and need treatment.

Deep vein thrombosis (DVT) is when a blood clot forms in a deep vein, usually the leg.

If a blood clot breaks away from the DVT and travels to another part of the body it can block a blood vessel. This can be harmful because it stops blood flow to parts of the body.

If a blood clot travels to the lungs it is known as a pulmonary embolism (PE).

3. The risk of blood clots in people with breast cancer

People with breast cancer have a higher risk of blood clots than those without cancer.

This is because cancer releases a higher number of platelets and clotting factors. These play a role in helping the blood to clot and stop any bleeding. Having higher than normal amounts of platelets and clotting factors in the body means the blood is more likely to clot.

Some people with cancer may also have lower levels of proteins in the blood that help to keep it thinned. This means a blood clot may be more likely to form, particularly if the cancer affects the liver.

4. Breast cancer treatments that increase the risk of blood clots

Some treatments for breast cancer may increase the risk of developing a blood clot. These include:

  • Surgery – the risk of developing blood clots is highest 2–10 days after surgery and remains higher than normal for up to 90 days
  • Chemotherapy – as cells are destroyed by chemotherapy they can release substances that cause blood clots
  • Targeted therapies such as palbociclib and trastuzumab emtansine
  • Hormone therapies such as tamoxifen and fulvestrant

Both surgery and chemotherapy can damage the walls of blood vessels, which can increase the risk of a blood clot developing.

If you’re due to have surgery or chemotherapy, let your treatment team know if you have a previous history of blood clots.

Having a central line

A central line is a tube that’s inserted into a large vein and can be used to give chemotherapy or other drugs. Blood samples can also be taken from a central line.

If you have a central line, such as a Hickman line, PICC line or port, it’s possible for a blood clot to form in a vein at the end of the line. If this does happen the line may need to be removed.

Being less active due to treatment

For some people, their breast cancer treatment can make them feel very tired and weak, or cause some muscle and joint pain. This means they’re not as physically active. If you have surgery, it may be difficult to move around as much as you would normally at first. You can scroll down to section 8 on this page for more information.

Inactivity increases the risk of a blood clot as the normal action of the leg muscles helps squeeze the veins to return the blood back towards the heart.

Inactivity on long journeys, such as long-haul flights, can also increase the risk of developing a blood clot.

You can find out more about DVT and how to reduce your risk on the NHS website.

5. Other factors that can increase the risk of blood clots

Other things that can increase the risk of blood clots include:

  • Heart disease
  • Diabetes
  • Smoking
  • A previous history of blood clots
  • Fractures
  • Being overweight
  • Dehydration

There is no evidence that having the Covid-19 vaccine while having breast cancer treatment will increase your risk of blood clots.

6. Reducing the risk of blood clots

There are ways you can help to reduce your risk of developing a blood clot:

  1. Regular physical activity – take short walks or do some simple leg and foot exercises if you are unable to move around much
  2. Drink plenty of water to keep hydrated
  3. Eat a balanced diet and try to maintain a healthy weight
  4. Take particular care on long-haul flights or on a lengthy car journey – move around regularly, keep hydrated and use flight socks

7. Treating blood clots

Blood clots are usually treated with drugs that thin the blood (anticoagulants). The drugs will be given as an injection at first then may be changed to a tablet. These allow the body to absorb the blood clot over time and reduce the risk of future blood clots.

There are different drugs that thin the blood and your treatment team will choose the right one for you.

Treatment will usually be recommended for 3 to 6 months, but it may be longer based on your individual situation.

8. If you are in hospital

If you’re having an operation, you may be advised to stop taking particular medicines for a period of time before surgery.

If you need to stay in hospital, your risk of developing a blood clot should be assessed.

You may be given anti-embolism or compression stockings to wear which help the blood return towards the heart.

In some situations, for example straight after surgery, a device called an intermittent compression system is used to do this for a short time.

9. Further support

If you think you may have a blood clot contact your treatment team or go to your local A&E department straight away.

If you are concerned about blood clots or just want to talk things through, our specialist team are ready to listen on our free helpline, below.

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Quality assurance

This information was published in August 2022. We will revise it in August 2024.

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