Cancer and the risk of blood clots
Cancer can increase the risk of developing blood clots. Doctors often give blood clots different names depending on where they start. You may hear them say:
- deep vein thrombosis (DVT)
- pulmonary embolism (PE)
- venous thromboembolism (VTE)
What is a blood clot?
A blood clot is a collection of blood that can form inside a blood vessel (a vein or an artery). It can block the normal flow of blood. The medical name for a blood clot is thrombus.
Blood clots can develop in different parts of the body. When a blood clot forms in the deep veins of the leg it is called a deep vein thrombosis (DVT).
Part or all of a DVT can break off and travel around the body. It may travel through your heart to block part or all of the blood supply to the lungs. If this happens, it’s called a pulmonary embolism (PE). DVTs and PEs together are sometimes called venous thromboembolism (VTE).
Doctors can successfully treat most blood clots when diagnosed. So it's important to know about the symptoms of blood clots and report them to your doctor or nurse immediately.
Common symptoms of blood clots include:
- unexplained pain in your leg or arm
- redness and swelling in your leg - this may be just in the calf or include the whole of your leg
If a blood clot has moved to your lungs (a pulmonary embolism), the symptoms include:
- feeling breathless - this might start suddenly or increase over time
- pain in your chest or upper back which gets worse when you breathe in
- coughing up blood
- feeling light headed
Who is at risk of blood clots?
People with cancer have a higher risk of developing blood clots. Researchers think that up to 20 out of every 100 people with cancer (up to 20%) develop a blood clot at some point.
There are a number of reasons for this:
The cancer itself
People with cancer often have sticky blood. This may be because cancer cells make chemicals that stimulate the body to produce clotting factors.
Clotting factors are proteins made naturally by the liver. They combine with platelets to form blood clots and help us stop bleeding.
The type of cancer you have
You are at a higher risk of developing blood clots if you have one of the following types of cancer:
Also, the risk is higher in cancers that have spread to nearby lymph nodes or other parts of the body.
Certain cancer treatments can increase the risk of developing blood clots. These include:
- the chemotherapy drug cisplatin
- tamoxifen which is a type of hormone treatment for breast cancer
Your doctor will explain if the treatments you are having increase the risk of blood clots. They make sure the benefits of these treatments outweigh the risks.
Blood clots can also form in long lines such as central lines and PICC lines. These lines usually stay in your veins for many months. So you don’t need to have needles into your hand or arm each time you have cancer drug treatment.
Being less active
Cancer and its treatment can make you feel very ill. You can feel too tired and weak to move around as much. The blood flow in your leg veins depends on the squeezing of the veins by leg muscles when you walk. Immobility reduces the blood flow in the legs and blood can stagnate in the legs and become sticky.
So moving around helps reduce the risk of clots. As does doing exercises with the calf muscles such as moving your foot up and down.
After cancer surgery, you may not be able to move around much. Your nurses will give you a pair of elastic stockings to wear. These help to prevent blood clots. You need to wear these until you are moving around fully. This may be for a few weeks after your operation.
Long journeys, such as long haul flights, or long bus or car journeys can also increase the risk of clots.
Other factors that increase the risk of developing a blood clot include:
- taking the oral contraceptive pill or hormone replacement therapy (HRT)
- certain medical conditions such as diabetes or heart disease
- being overweight
Treating blood clots
Treatment for blood clots is usually drugs that thin your blood (anticoagulants). They don't break up an existing clot but prevent it from growing bigger and others forming. This allows the body to gradually break the clot down and reabsorb it.
You usually take anticoagulants for 3 to 6 months.
The most common types of anticoagulants are:
Direct oral anticoagulants (DOACs)
These are new types of blood thinners that mean you don't need to have regular blood tests. They are also used to prevent stroke and to treat blood clots in people who don't have cancer.
Low molecular weight heparins
You have low molecular weight heparins as an injection under the skin (subcutaneously). You may need regular blood tests.
Warfarin comes as a tablet. They are a type of anticoagulant called vitamin K antagonist (VKA). Doctors most often prescribe warfarin to people who have a heart condition called atrial fibrillation. This causes an irregular and fast heart rate.
It takes several days for warfarin to work so you may also have heparin first. You may take warfarin for a few weeks or months. You have regular blood tests to check that your blood is not getting too thin or too thick.
This is a fast acting heparin. You usually have it directly into your bloodstream (intravenously). You might have it when you're first diagnosed with a blood clot, especially if your kidneys are not working very well.
Reducing the risk of a blood clot while in hospital
The National Institute of Health and Care Excellence (NICE) has guidance about reducing the risk of blood clots for people in hospital.
When you are in hospital, your doctor or nurse will assess your risk of developing blood clots. They will suggest you have preventative treatment if you are at higher risk of developing blood clots. This might include:
- taking drugs that thin your blood (anticoagulants)
- wearing elastic stockings (anti embolism stockings)
- using compression devices (intermittent pneumatic compression)
- seeing a physiotherapist to help you get out of bed and move around as soon as possible
- stop taking certain drugs such as the combined oral contraceptive pill or hormone replacement tablets
- having fluids so that you don't become dehydrated
Anti embolism stockings
You may be given anti embolism stockings to wear until you are moving around as usual. These are tight stockings that squeeze your feet and legs, helping the blood to circulate more quickly. Your nurse will measure your legs to make sure you have the right size.
You cannot usually wear these stockings if you have:
- fragile skin, eczema or recently had a skin graft
- narrowing of the blood vessels leading to your legs (peripheral arterial disease)
- swollen legs
- recently had a stroke
- tingling or numbness in your fingers or toes (peripheral neuropathy)
Intermittent pneumatic compression
Your doctor may suggest you use an intermittent pneumatic compression device. You wear this around your legs and feet. It inflates regularly to keep the blood circulating well. You use this while you are in bed or in a chair.
Your doctor or nurse will tell you if you need to wear stockings or take blood thinners at home. They will advise you how long to take treatment for and who to contact if there are any problems.
If you've had major surgery to your tummy (abdomen) or pelvis, you have injections of heparin for 4 weeks after your operation. You have them every day as an injection under the skin (subcutaneous injection). Your nurse will show you how to do it before you go home.
The video below shows you how to give a subcutaneous injection. The video is 3 minutes long.
Nurse: This is a short film showing you how to give an injection just under your skin. This is called a subcutaneous or sub cut injection. This does not replace what your doctors and nurses tell you, so always follow their advice.
Voiceover: Subcutaneous injections may be part of your cancer treatment. Or, you may need them to prevent side effects of treatment, such as blood clots after surgery. Or to help control cancer symptoms, such as pain or sickness.
Most injections come in prefilled syringes.
Nurse: So, today I am going to show you how to give a subcutaneous injection. I am going to start by giving it into a practice cushion and then you can have a go at giving one yourself. Before you start, you need to get your equipment together. What you are going to need is an alcohol wipe to clean your skin, some cotton wool, a prefilled syringe and a sharps bin. It is important that you wash your hands with soap and water and dry them thoroughly before you start. Check that you have got the correct drug and that it is in date.
You can give the injection into the back of your arm, your tummy, your thigh or the outer part of your bottom. It is important that you vary where you give the injection. So it may be that you give it one day in your tummy and the next in your thigh.
So you start by cleaning the skin with the alcohol wipe and allowing it to air dry. Then you take the cover off the needle and pinch the skin up and hold it a bit like a pen and in an upright position, in a quick dart like motion pop it straight down into the skin. Then you press the plunger right to the end, quickly pull the needle out, dab it with cotton wool, pop the needle into the sharps bin. And then you need to wash your hands again.
So here’s what you are going to need. If you start by checking the drug and the expiry date. And then with the alcohol wipe give your skin a clean. That’s it give it a few seconds for the air to dry it. Ok and then if you want to pick up the syringe and take the cover off the needle. Then pinch your skin up and at a ninety degree angle gently push the needle in...then press the plunger...and then quickly remove it... dab your skin with the cotton wool and put the syringe in the sharps bin.
Tips for preventing blood clots
- take short walks as often as possible
- keep active
- do simple leg exercises like bending and straightening your toes every hour if you can't move around much
- drink plenty of water
- report any symptoms to your doctor or nurse straight away
The risk of developing a blood clot is higher in the first few months after being diagnosed with cancer. You might worry about how this complication will affect your cancer treatment.
It is important to understand that often blood clots are a normal part of the cancer journey. It’s normal to feel anxious about experiencing one.
Remember that doctors can successfully treat blood clots when diagnosed. This should not interfere with your cancer treatment.