Side effects of cancer drugs
ICANS is a side effect of some treatments, most commonly . It is caused by affecting the brain and the . It is not fully understood why it happens, but researchers are learning more about it all the time.
ICANS is also known as a neurological side effect or neurotoxicity.
ICANS symptoms vary from being mild to severe and life threatening.
Having symptoms that affect the brain and central nervous system can feel quite scary. We know that some people understand or are aware of when they have symptoms of what is happening to them. But for others, the changes are not noticeable to them and are picked up by the people looking after them.
Your healthcare team do what they can to prevent ICANS happening. You’re monitored closely before and after treatment. And you’re looked after by healthcare professionals with experience in ICANS if you have symptoms.
The most common treatment for ICANS is . Steroids usually work well to reverse the symptoms. But you might need to have other medicines to help.
CAR T-cell therapy is the most common cause of ICANS. But it can also happen with cancer drugs called . Examples of BiTEs are:
blinatumomab
teclistamab
glofitamab
epcoritamab
tebentafusp
Find out more about these medicines on the cancer drugs A to Z list
ICANS commonly develops around 5 days after CAR T-cell therapy. For some people, it can happen more than 3 weeks after you have your CAR T-cells. But this is rare.
It is not so clear when symptoms might happen with other treatments. Your team monitors you closely if you’re having a treatment that could cause ICANS.
ICANS symptoms can develop slowly over a few days or very quickly. ICANS can develop differently in people having the same treatment.
It is also not easy for doctors to diagnose ICANS. The symptoms can be similar to those caused by other things such as:
the cancer itself
infection
cancer treatment
The following are some of the common symptoms of ICANS. You may have more than one. They include:
shaking and worsening of your handwriting
changes to your personality or behaviour such as confusion, agitation and feeling disorientated
changes in your speech, such as difficulty finding the correct word. You might also find it difficult to understand what people are saying
problems with coordination and balance
Other symptoms may include:
seeing things that aren’t there (hallucinations)
headaches
changes to how awake and aware you are
tiredness and weakness (fatigue)
feeling or being sick
changes to your eyesight
ICANS can also cause seizures (fits), but this is less common. You may have a medicine to prevent seizures from happening.
Not everyone having CAR T-cell therapy or BiTEs will develop ICANS. But there are people who are at higher risk. Even if you have risk factors it doesn’t mean that you will definitely develop ICANS.
You are at higher risk if you:
have a large number of cancer cells - this is also called a high tumour burden
had to remove your before CAR T-cell treatment, meaning that you had very low levels of
have existing problems affecting the brain
had very early on after treatment and it was severe
have certain types of blood cancer – such as acute lymphoblastic leukaemia (ALL)
The type of CAR T-cells that you have can also increase the risk of developing ICANS.
Your doctor will let you know more about your individual risk.
There is no test that can definitely say you have ICANS. Your doctor builds up a picture based on:
your signs and symptoms
a
tests or scans to rule out other possible health issues
your
Your doctor may also involve other health professionals with expertise in ICANS.
During and after treatment one of your healthcare team will ask questions to check:
your memory
if you can follow commands
that you know where you are and what month and year it is
your level of awareness
They also ask you to write a sentence.
They score each question and task. This gives an immune effector cell encephalopathy (ICE) score. They use this to grade your ICANS. Your healthcare team usually checks your ICE score 2 or 3 times a day.
Other tests or scans you might have include:
- these are tests to check your nervous system
blood tests
a brain scan, such as an
a test to record the electrical activity of the brain. This is called an electro encephalography (EEG)
a
an eye examination, including an examination of the back of your eye (fundoscopy)
Your doctor puts all the tests results together to work out the grade. This shows the severity of the ICANS.
The grading of ICANS includes:
your ICE score
if you are having any seizures (fits)
your level of awareness (consciousness)
your muscle strength and tone
your reflex reactions and if you have any movements you can’t control, such as tremors
if you have a change in
any swelling to the brain that can be seen on scans
There are 4 grades ranging from grade 1 to grade 4. Grade 1 being mild and grade 4 being the most severe. Knowing the grade helps your doctor decide the treatment that you need.
Treatment for ICANS is individual to each person, and it depends on the severity of the symptoms. Mild cases may just need monitoring. More severe cases will need treatment.
The main treatment is steroids to reduce inflammation. Generally, you start to see an improvement in your symptoms after about 3 days. If the symptoms get better, your doctor then slowly lowers your steroid dose. Stopping them suddenly can cause serious side effects.
For some people the steroid dose may need to go up again if the symptoms get worse.
You might have a type of cytokine immunotherapy treatment called anakinra if steroids aren’t helping.
Other treatments you might have for ICANS include:
a medicine to help prevent and reduce seizures
stopping or delaying the treatment you are having. This might include permanently stopping the cancer drug, but this depends on the severity of ICANS
staying in the for support and one to one nursing care
other medicines that change how the immune system works
You might also need other supportive treatments. These are to help treat the effects of the immunotherapy treatment or the symptoms of ICANS.
The problems you have depend on how the treatment and symptoms are affecting your body. You might have some of the following supportive treatments:
antibiotics and antifungal medicines for treating and preventing infections
for low levels of
for low levels of
drips (intravenous infusions) for fluids if you are unable to eat and drink properly
oxygen through a mask to help increase your oxygen levels in the body
Find out more about other side effects of treatment
Most people recover well after ICANS. But it can feel overwhelming for some time afterwards as you have been through a lot. Not only are you trying to cope with the side effects of ICANS and other aspects of your treatment, but also with having cancer itself.
You can feel different to how you felt before cancer. It’s normal to find treatment mentally and physically challenging.
Everyone copes differently and there are ways to get support that suits you. Your nurses and the rest of your healthcare team are there to help so do talk to them about how you are feeling and if you have any questions.
Go to our information about where to get support
There is a risk that ICANS can happen later than 3 weeks after CAR T-cell therapy. This is called delayed ICANS.
You shouldn’t drive for between 4 to 8 weeks after the day you had the cells. This is because ICANS can develop very quickly when it happens.
The amount of time you should not drive for depends on the type of CAR T-cell therapy you had. Speak to your treatment team about how long you should not drive for.
Researchers around the world are looking into:
understanding more about why ICANS happens
ways to prevent it from happening
ways to diagnose it quickly
different treatments for ICANS
Talk to your doctor or clinical nurse specialist to find out more about clinical trials. You can also search for a clinical trial on our clinical trials database.
Last reviewed: 25 Jun 2026
Next review due: 25 Jun 2029
Immunotherapy uses our immune system to fight cancer. It works by helping the immune system recognise and attack cancer cells.
CAR T-cell therapy is a type of immunotherapy. It is also called adoptive cell transfer. It's a possible treatment for some children and adults with leukaemia. It is also a treatment for some adults with lymphoma.
Monoclonal antibodies (mAbs) are a type of cancer treatment. They may be called a type of targeted cancer drug or immunotherapy. But they can work in both ways. Find out more.
There are many cancer drugs, cancer drug combinations and they have individual side effects.
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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