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CAR T-cell therapy changes your immune cells to help them fight your cancer. It's a treatment for diffuse large B-cell lymphoma (DLBCL) that didn't respond to other treatments or that came back afterward. But it can cause side effects. Some side effects are mild. Others may be life-threatening and will need treatment right away.

You'll have tests to make sure CAR T-cell therapy is right for you. You may stay in the hospital for at least a week after treatment so that your medical team can closely monitor you for any problems and manage them. Even though some side effects are serious, they usually go away and don't leave any long-term effects.

Cytokine Release Syndrome (CRS)

Cytokines are proteins that act like messengers. They tell your immune system how to respond to germs and other threats.

As your new CAR T cells multiply, they cause an immune response in your body. Your immune system releases large amounts of cytokines into your blood to attack the cancer. This flood of cytokines causes inflammation all over your body.

Most people who have CAR T-cell therapy will get CRS. Another name for it is "cytokine storm." Usually, it isn't serious.

CRS starts in the first 2 weeks after treatment. Because it mimics the effects of your immune system attacking a virus, it feels like you have a bad case of the flu.

These symptoms usually start 1 to 5 days after the T-cell infusion. They usually last for about a week but may last longer, depending on the methods used to treat it. Doctors can usually treat them with pain relievers like acetaminophen and fluids through an IV.

Tocilizumab (Actemra) is a treatment for CRS. It works quickly to bring down inflammation.

CRS sometimes causes more serious side effects like:

  • Fast heartbeat
  • Low blood pressure
  • Trouble breathing

While side effects from CRS usually respond to treatment, they can be life-threatening. If your symptoms are severe, you'll need treatment in a hospital intensive care unit (ICU). You'll get oxygen, medications, and fluids to control your symptoms.

Problems With the Brain

CAR T cells can also affect your brain and nervous system. It isn't very common, but it can be serious. Most of these possible nervous system problems are together known as immune effector cell-associated neurotoxicity syndrome, or ICANS.

Symptoms include:

  • Headache
  • Confusion
  • Trouble speaking/language impairment (aphasia)
  • Seizures
  • Shaking (tremors)
  • Balance problems

These symptoms typically start 1 to 10 days after you have CAR T-cell therapy and last about 2 weeks, but they can last 4-8 weeks. Though this side effect can be scary, it usually gets better in a few days and doesn't cause any long-term problems. You'll get steroid medicines to bring down inflammation in your brain. Because the symptoms affect how your brain functions, you won’t be able to drive, operate machinery, or do anything that could possibly be dangerous for about 8 weeks after being treated.

Tumor Lysis Syndrome (TLS)

CAR T-cell therapy releases millions of new T cells into your body to kill your cancer cells. As the cancer cells die, they release toxic chemicals that can harm organs like your kidneys, heart, and brain.

Symptoms of tumor lysis syndrome include:

  • Nausea and vomiting
  • Loss of appetite
  • Fatigue
  • Dark urine
  • Numbness
  • Seizures

Because it takes time for the cancer cells to die, you might not have symptoms for a month or more after CAR T-cell therapy. Your doctor will watch for this side effect and treat you with fluids and medicines in the hospital if it happens.

Allergic Reactions

Some people have an allergic reaction to the CAR T cells during the treatment or soon afterward. A small number of them have a severe allergic reaction called anaphylaxis. They have symptoms like hives, swelling of the face, a drop in blood pressure, and trouble breathing.

Anaphylaxis can be life-threatening. You'll be monitored closely during treatment for this side effect. If it happens, you'll get treatment right away, which may be a shot of epinephrine.

B-Cell Aplasia

B cells are immune cells that help your body fight infections. CAR T cells target a protein that is on the surface of both cancer cells and B cells. Sometimes they can destroy B cells while attacking your cancer. Having fewer B cells makes it harder for your body to fight infections.

Electrolyte Imbalance

Another possible side effect of CAR T-cell therapy is low levels of certain minerals in the blood, including sodium, phosphorous, and potassium. Low levels of these minerals can cause serious medical problems.

When there isn’t enough sodium in your blood, water moves into your body’s cells very quickly in a condition called hyponatremia. Your cells swell up with this excess water, including your brain cells. If untreated, this can lead to confusion, headaches, and nausea. In severe cases, it can cause coma, and even death. Your doctor will track your blood chemical levels carefully. Hyponatremia may be treated with a saline IV or medications.

Show Sources

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American Cancer Society: "CAR T-Cell Therapy and Its Side Effects."

Cancer Research UK: "CAR T-cell therapy."

Cleveland Clinic: "CAR T-Cell Therapy," “Hyponatremia.”

Dana-Farber Cancer Institute: "CAR T-Cell Therapy for Lymphoma." "What Are The Side Effects of CAR T-Cell Therapy?"

JAMA Oncology: "Tumor Lysis Syndrome."

Leukemia & Lymphoma Society: "Chimeric Antigen Receptor (CAR T-Cell Therapy."

Mayo Clinic: "About CAR-T Cell Therapy,” “Hyponatremia.”

MD Anderson Cancer Center: "CAR T cell therapy side effects in lymphoma patients."

Memorial Sloan Kettering Cancer Center: "CAR T Cell Therapy: A Guide for Adult Patients and Caregivers."

Rutgers Cancer Institute of New Jersey: "Side Effects of CAR T-Cell Therapy."

St. Jude Children's Research Hospital: "Cytokine Release Syndrome (CRS) After Immunotherapy."

National Comprehensive Cancer Network: “Immunotherapy Side Effects: CAR T-Cell Therapy.”