Breathing problems with cancer
If you have existing problems with breathlessness and it gets worse, your healthcare team will want to know. Contact the advice line at your hospital.
New shortness of breath when you are resting can be an emergency.
You can feel breathless if you have cancer in or near your lungs. This includes:
cancers such as lung cancer or mesothelioma
cancer that has spread to the lungs from other parts of the body (advanced cancer or ).
Cancer near the lungs can also put pressure on your . This might narrow or block the tubes carrying air into your lungs, making it difficult for air to come through. This makes it difficult to breathe normally.
A blockage in the upper airways can cause noisy breathing. This is called stridor. You might be able to hear the air going in and out past the blockage.
Surgery to remove part of your lung, a lobe of your lung, or one of your lungs, can affect how well you breathe.
If you are having surgery on the lung, you may worry that you will have a lot of difficulty breathing after the operation. This is not always the case.
Depending on how much of the lung you have left, you may still be able to breathe quite normally. If you were short of breath before your operation, you may still have some breathing problems afterwards.
Your doctor considers several factors before they decide which type of lung surgery is best for you and if you are fit enough to have surgery.
Find out more about types of surgery for lung cancer
The side effects of some anti cancer drugs can cause breathlessness. This might be due to:
inflammation and scarring of the lungs
an allergic reaction causing you to become suddenly short of breath
an infection due to a low level of white blood cells
Some drugs are more likely to cause breathing problems. For example, can sometimes lead to inflammation of the lungs, called . Pneumonitis can happen within days of starting immunotherapy, or months or years after starting.
Your healthcare team are aware of the side effect of the drugs you have. They will explain the risk of becoming breathless and check you regularly for any problems.
It is important to let your doctor or nurse know straight away if you have any breathing problems during or after your treatment.
Drug treatments that may cause breathlessness include:
chemotherapy drugs such as bleomycin, methotrexate and gemcitabine
immunotherapy drugs such as nivolumab, pembrolizumab and durvalumab
targeted cancer drug such as cabozantinib, trastuzumab and bevacizumab
Read more about cancer drugs and their side effects
Having radiotherapy to the chest can cause:
shortness of breath
inflammation of the lung (pneumonitis)
These side effects can start during your treatment and often also continue afterwards. They will usually improve a few weeks after your treatment finishes. But they can be a long term problem for some.
Read more about breathlessness during and after radiotherapy
Cancer can cause fluid to collect around the lung. This is called pleural effusion.
There are two sheets of tissue that protect the lungs. They are called pleural membranes or pleura. It is normal to have a thin layer of fluid in the space between the pleura (pleural space).
When cancer affects the lungs, fluid can sometimes build up in the pleural space. The fluid stops your lungs from expanding fully. So you have to take shallower breaths and make more of an effort to breathe.
Find out about the causes and treatment of fluid build up in the lungs
Some advanced cancers can cause fluid to build up in the tummy (abdomen). This is called ascites. This fluid can cause pressure on the . This then puts pressure on the lungs and causes breathlessness.
Most heart problems that cause breathlessness are not related to cancer. They are often caused by other medical conditions such as congestive heart failure. But sometimes cancer or its treatment does cause heart problems that lead to breathlessness. This might be because:
the cancer is putting pressure on your heart
side effects from anti cancer drugs or radiotherapy may affect your heart
Some types of cancer can grow very near the tissue that surrounds and protects your heart (the pericardium). This can interfere with how much blood the heart can pump out and may make you short of breath.
Some cancer medicines can affect the heart, which may then lead to breathing problems. Your doctor will let you know if any of the drugs you are taking might cause heart problems. You have regular tests during your treatment to check how well your heart is working if:
your cancer medicines are known to affect the heart or
you have any symptoms
There is a chance that a small part of the heart might be in the radiotherapy treatment area if you have radiotherapy to the left side of the chest. This is less common now as newer radiotherapy techniques are available.
The heart is sensitive to radiation. Another side effect of having radiotherapy near the heart is a build-up of fluid around the heart (pericardial effusion). This can cause breathlessness. If this happens, you may need a procedure to drain the fluid.
The superior vena cava (SVC) is a large blood vessel in the middle of the chest. It carries blood from the head, neck and arms to the heart. This vessel might become blocked. This is called superior vena cava obstruction (SVCO). The most common symptom is shortness of breath.
It can happen in different cancers including:
lung cancer
breast cancer
non-Hodgkin lymphoma
Blockage of the blood vessel (SVCO) can be caused by:
a blood clot within the blood vessel
the cancer pressing on the blood vessel
cancer in the nearby lymph nodes, making them larger and pressing on the blood vessel
The pressure on the blood vessel stops blood going back to the heart from the head and arms. This causes swelling around your windpipe (trachea) making breathing difficult.
Symptoms of blood vessel blockage in the neck include:
breathlessness
swelling of the face, voice box (larynx), neck, and arms
chest pain
a cough
dizziness
eyesight changes
headache
confustion
You need urgent treatment for SVCO. You will have oxygen and medicines to reduce the swelling and relieve other symptoms.
You may have:
a thin tube called a stent put into the vein to keep it open
radiotherapy or chemotherapy to try and shrink the cancer and stop it pressing on the superior vena cava
Your makes . These cells are part of your immune system and help your body to fight infection.
Cancer cells and cancer treatment can damage your bone marrow. If you don't have enough white blood cells, you have a higher risk of getting an infection.
Some infections and in particular a chest infection will affect the way you breathe. If you have a serious infection, such as pneumonia, breathing will be even harder.
Infection during cancer treatment can be very serious and can be life threatening. Contact your hospital advice line immediately if you have a raised temperature or other signs of infection.
Find out more about infections and cancer
Red blood cells are made in your bone marrow. They contain which carries oxygen around your body. When the level of haemoglobin in your blood is low, you have anaemia.
Anaemia makes you very tired. And you may also become breathless because your blood is carrying less oxygen.
A blood clot is a clump of blood cells 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).
Feeling breathless is a common symptom if you have a PE. This might start suddenly or increase over time.
Other symptoms of a clot in the lung include:
pain in your chest or upper back
lightheadedness
coughing up blood
Find out more about cancer and the risk of blood clots
Cachexia is a complex change in the body, causing you to lose weight despite eating normally. Many people with advanced cancer have cachexia.
Cachexia can cause changes in breathing because the muscles that help with breathing are weaker.
You may have shortness of breath when you are very anxious or get panicky. It might help to try breathing and relaxation techniques. These can help you feel more in control of your breathing.
Find out more about breathing and relaxation techniques
Other medical conditions can cause breathlessness. These include:
lung diseases such as emphysema or chronic obstructive pulmonary disease (COPD)
asthma
pain
a collapsed lung
Last reviewed: 11 Aug 2026
Next review due: 11 Aug 2029
The type of treatment you need depends on the cause of your breathlessness. Find out about treating breathlessness, including treating fluid on the lung (pleural effusion).
Coping with cancer can be difficult. There is help and support available. Find out about the emotional, physical and practical effects of cancer and how to manage them.
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Many people with cancer have shortness of breath at some time during their illness. Symptoms of breathlessness include difficulty catching your breath, noisy breathing and anxiety or panicky feelings.
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