CAR T therapy boosts your immune system to help it fight your cancer. It's a promising treatment for follicular lymphoma that didn't respond to other therapies or that came back afterward. But it does come with side effects. Some are mild. Others are more serious.

You'll go through careful screening before you have this treatment to make sure that it's right for you. And you may stay in the hospital several days or weeks afterward so that your doctors and nurses can keep a close eye on you. Your doctor will check on you regularly for a few months after your procedure.

Cytokine Release Syndrome

Cytokines are proteins your cells release that direct your immune system to fight infections and cancer. After you get CAR T therapy, the modified T cells multiply in your body. They trigger a huge release of cytokines into your blood.

The name for this is cytokine release syndrome (CRS), or cytokine storm. Cytokines produce inflammation that can harm organs like your heart, lungs, kidneys, liver, and brain.

CRS usually starts a few days to a few weeks after CAR T therapy. Because the T-cells are doing what they'd do if they were fighting a virus, you might feel like you have the flu, with symptoms like:

  • A fever
  • Chills
  • Tiredness and weakness
  • Vomiting and diarrhea
  • Appetite loss
  • Joint or muscle aches

CRS can also cause more serious side effects like these:

  • Low blood pressure
  • Very fast or abnormal heartbeat
  • Low oxygen
  • Heart failure
  • Kidney problems

Not everyone will have these symptoms. CRS is milder in some people than others. It's a sign that the new CAR T cells are working in your body.

CRS usually lasts only a week, but if your symptoms are severe enough, you'll need treatment in an intensive care unit (ICU). You'll get oxygen, fluids, and medications to control your symptoms. Steroids and other medicines can help lower the immune response and bring down inflammation in your body.

Problems With the Brain

Side effects from CAR T therapy are more serious when they affect your brain. Cytokines can harm brain cells, which your doctor might call neurotoxicity. This side effect starts 1 to 4 weeks after treatment and lasts for a few days.

Symptoms include:

  • Headache
  • Memory loss
  • Dizziness
  • Confusion or hallucinations
  • Trouble speaking
  • Shaking
  • Seizures

This side effect can be very scary, but it is reversible most of the time. In a hospital, you'll get steroids and other medicines to bring down inflammation in your brain. Most people get better within a few days and don't have any long-term effects.

Tumor Lysis Syndrome (TLS)

The millions of CAR T cells released into your blood during treatment quickly go to work to kill lots of cancer cells. As these cancer cells die, they release toxic substances that harm organs like your liver and kidneys.

Because it can take some time for the cancer cells to die, tumor lysis syndrome may not happen until a few weeks after your treatment. Your doctor will monitor you for this side effect and treat you with fluids and medicines if it happens.

Infusion Reactions

Some people have an allergic reaction to the CAR T cells during treatment or right afterward. Symptoms of this reaction are usually mild and can include nausea and vomiting.

A small number of people have a severe allergic reaction called anaphylaxis. They get symptoms like hives, swelling of the face, trouble breathing, and a sudden drop in blood pressure. Anaphylaxis is life-threatening and needs to be treated right away. Most often, this is with a shot of epinephrine.

B-Cell Aplasia

CAR T therapy targets proteins called antigens on the surface of cancerous B cells. These antigens are also on the surface of the healthy B cells that protect your body from infection.

CAR T therapy can kill some normal B cells along with the cancer. This leaves you at higher risk for infection. You may get immunoglobulin replacement therapy -- a treatment that gives you more antibodies so you can fight infections until your body recovers from CAR T therapy.

Cytopenia

Some people get chemotherapy before CAR T therapy to get their body ready for the treatment. Both chemotherapy and the release of cytokines after CAR T therapy can cause a drop in your blood cell count, called cytopenia.

The white blood cells that help your body fight infections are most often affected. A low white blood cell count is called neutropenia. Sometimes you might have fewer platelets that help your blood clot, called thrombocytopenia.

Cytopenia doesn't always need treatment. But if your blood cells drop very low, you may need a blood transfusion or medicines to boost your blood cell count.

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