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Serious side effects of CAR T-cell therapy


What is CAR T-cell therapy?

CAR T-cell therapy is a type of cancer treatment.

The information below tells you about 2 possible side effects of this treatment. These side effects are serious, and they can be dangerous. The St. Jude team will watch out for them and treat them if they happen.

What is cytokine release syndrome?

The first serious side effect is called “cytokine (syh-toe-KINE) release syndrome.” Doctors also call it CRS.

Cytokines are chemicals that tell the immune system to work. CAR T-cell therapy can send a lot of these chemicals into the bloodstream quickly. This happens as the immune system starts working very hard to fight the cancer. It can happen in the one (1) or 2 weeks after your child gets CAR T cells.

Doctors will watch your child closely for signs of CRS.

What are the signs of CRS?

A fever is the main sign of CRS. Tell your child’s doctor or nurse right away if your child has a fever.

Other signs of CRS include:

  • Chills,
  • Headache,
  • Fast breathing or trouble breathing,
  • Loss of appetite, nausea, vomiting, or diarrhea,
  • Fatigue (feeling very tired),
  • Pain in the joints, muscles or both, and
  • Low blood pressure – Your child might feel dizzy or lightheaded.

What is the treatment for CRS?

Your child will probably need to be admitted to the hospital. Your child’s doctors and nurses will keep your child as comfortable as possible. They might give medicine to control fever and blood pressure problems. They might also give your child a medicine designed to treat an overactive immune system.

What is neurotoxicity?

Neurotoxicity (NUR-oh-tok-SIS-uh-tee) is a medical term that means something is toxic to the nervous system. Your nervous system includes the brain, spinal cord, and nerves. Neurotoxicity can be very serious because these are important parts of the body.

Doctors will watch for signs of neurotoxicity if your child has CAR T-cell therapy. This is because some people in CAR T-cell research had these signs. They included confusion, brain swelling, and seizures. Not everyone had them, and they were mostly temporary. Neurotoxicity can happen in the first one (1) or 2 weeks after treatment, or as long as 4 to 6 weeks afterward.

Signs of neurotoxicity

Tell your child’s doctor or nurse right away if you notice any of these signs.

  • Confusion
  • Headache
  • Hallucinations (seeing things that are not there)
  • Shakiness
  • Problems walking, weakness, or coordination problems
  • Problems talking
  • Temporary memory problems
  • Feeling sleepy
  • Feeling dizzy
  • Seizures

Will my child have both these side effects?

Not necessarily. Neurotoxicity and CRS are separate problems. Your child might have one (1), both of them, or neither.

What should I do if I notice signs of CRS or neurotoxicity?

These side effects can be very serious. If your child shows any signs of CRS or neurotoxicity, please call B Clinic right away at 901-595-2138. We are open Monday through Friday, 8 a.m. to 5 p.m.

If you are calling after regular hospital hours, dial 901-595-3300 and ask for the doctor on call. Be sure to let the doctor know your child has had CAR T-cell therapy. If you are outside the Memphis area, dial toll-free 1-866-2STJUDE (1-866-278-5833).

What other things should I be aware of?

  • For at least 4 weeks, you must stay in the Memphis area within a 2-hour drive of the hospital.
  • Your child should not take part in hazardous activities and drive for at least 8 weeks after receiving CAR T-cell therapy.
  • This treatment can increase the risk of life-threating infections that can lead to death.
  • Within the first 2–3 months after receiving the CAR T-cell therapy if your child visits any health care providers, be sure to let them know your child recently had CAR T-cell therapy.


If you have questions about CAR T-cell therapy or side effects, ask your child’s doctor or nurse. 



This document is not intended to take the place of the care and attention of your personal physician or other professional medical services. Our aim is to promote active participation in your care and treatment by providing information and education. Questions about individual health concerns or specific treatment options should be discussed with your physician.

St. Jude complies with health care-related federal civil rights laws and does not discriminate on the basis of race, color, national origin, age, disability, or sex.

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