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What is CAR T-cell therapy?

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This is a brief guide to Chimeric Antigen Receptor T-cell (CAR T-cell) therapy, a type of therapy you may receive if your stem cell transplant or other treatment is unsuccessful.

We’ve split this guide into the following sections:

What are CAR T-cells?

T cells are a type of white blood cell that form an important part of your immune system. They recognise abnormal cells, such as cancer cells, and destroy them.

T cells destroy abnormal cells using proteins on their surface called receptors. They bind to proteins found on cancer cells but not on normal cells. Sometimes, cancer cells can survive by disguising themselves from being recognised by T cells.

T cells become CAR T-cells when scientists change the DNA of T cells to make them produce a new type of receptor, called a Chimeric Antigen Receptor (CAR).

CAR T-cells are more efficient at binding to and removing cancer cells. They also send out signals that attract other immune cells and cause them to rapidly reproduce near the cancer cells. This increases the chance of all the cancer cells being removed.

What happens during CAR T-cell therapy?

Collecting your T cells

Your T cells will be collected by a common procedure which can take a few hours. It may be need to be done more than once to collect enough blood cells.

  1. You'll have a needle in each arm.
  2. Your blood will be taken out of one arm and go into an apheresis machine.
  3. The apheresis machine will separate your white blood cells from the rest of your blood.
  4. The rest of your blood will be returned to your other arm.
  5. Your white blood cells are sent to the laboratory where the T cells are isolated and modified.

Forming your treatment

At the laboratory:

  1. Researchers will create your new CAR T-cells by modifying the DNA of your T cells.
  2. The cells will then be grown until there is enough of them to form your treatment. This can take a few weeks.
  3. When they're ready, your cells will be frozen and sent back to the hospital, ready for you to receive.

Before you receive your new cells

Around 10 days before your CAR T-cell treatment is due, you will be given a course of chemotherapy known as conditioning therapy. This removes any cancerous cells and prepares your body for the CAR T-cells.

Treatment day

Your new CAR T-cells will be thawed and delivered to you via your central line. It’s a similar process to having a blood transfusion. Afterwards, you will be monitored in hospital for a few weeks while you recover. Once discharged, you will need to stay within an hour’s drive of the hospital for a further four weeks.

Are there any side effects of CAR T-cell therapy?

CAR T-cell therapy is a very intensive treatment that will have a big physical and emotional impact on your life. After treatment, your medical team will monitor you closely because most side effects develop within the first few days – but some could occur up to eight weeks later. Side effects will vary from person to person but may include the following:

  • Cytokine release syndrome (CRS) – When CAR T-cells enter your body, they activate other cells in your immune system that help remove cancer cells. Sometimes this signalling can cause an inflammatory response across the whole body, known as cytokine release syndrome. CRS can cause high fevers and low blood pressure, and in very extreme cases has been known to be fatal.
  • Neurological problems – You may feel drowsy, have a headache, or find it difficult to do some mental tasks and remember things. These are all due to your body’s immune response to the CAR T-cells.
  • Low B cell count – Some CAR T-cell therapies target cancerous B cells, but they may destroy healthy B cells as well. These cells are part of your immune system and help fight infections, which means after treatment you may be at risk of picking up an infection.

Your medical team will talk to you about these side effects in more detail and give you advice on what to do if they start to develop. If you have any questions, they will be happy to answer them too.

Who can have CAR T-cell therapy?

CAR T-cell therapy has been approved to treat children and young adults with B cell acute lymphoblastic leukaemia (ALL) and adults with large B cell lymphoma, specifically:

  • relapsed or refractory diffuse large B cell lymphoma (DLBCL)
  • relapsed or refractory primary mediastinal large B cell lymphoma (PMBCL)
  • relapsed or refractory mantle cell lymphoma (MCL), where previous therapy includes a BTK-inhibitor.


CAR T-cell therapy is currently only offered if other treatments have been unsuccessful.

There are lots of other CAR T-cell therapies being tested in clinical trials right now. If the results are positive, these therapies may be available to more patients in the future.

You can have CAR T-cell therapy at a number of hospitals in the UK. You can find a list of these hospitals on the NHS website.

Can I join a clinical trial?

Clinical trials are a type of medical research study. They test new treatments in a group of patients before they’re approved for the NHS to use. They’re based in either one or a few hospitals throughout the country and can only accept patients based on the type of blood cancer they have and their treatment history.

You can search for current clinical trials on the Find a clinical trial webpage on the Cancer Research UK website.

Unfortunately, if you don’t meet the medical criteria the trial needs, you won’t be able to take part. Your medical team will be able to talk to you about suitable trials when the time comes.

Will CAR T-cell therapy replace stem cell transplants?

For some patients, it's possible that CAR T-cell therapy may become an alternative to stem cell transplants in the future. Other patients are likely to only be offered the treatment if their transplant is unsuccessful, or in addition to their transplant. However, it's difficult to make predictions at this early stage.

Where can I read more about CAR T-cell therapy?

You can read more about CAR T-cell therapy, including from patients themselves, on the following websites:

Information published: 17/11/22
Next review due: 17/11/23

Related links

Joining a clinical trial

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