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What to Expect With CAR T-Cell Therapy

A plain-language guide to CAR T-cell therapy and T-cell transfer therapy

NCI source:National Cancer Institute

Review status: AI-assisted, source checked. Not reviewed by a clinician. How we check pages

The short answer

CAR T-cell therapy is a type of T-cell transfer therapy that changes your own immune cells in the lab so they can better attack cancer. Your cells are collected, grown over weeks, and given back through a vein. It can cause serious side effects such as cytokine release syndrome.

  • T-cell transfer therapy makes your own immune cells better able to attack cancer.

  • The two main types are TIL therapy and CAR T-cell therapy.

  • Your T cells are collected, changed or selected and grown in the lab, then given back through a vein.

  • Growing the cells can take 2 to 8 weeks, and you may have chemotherapy first.

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The simple version

CAR T-cell therapy is a type of T-cell transfer therapy. T-cell transfer therapy is a kind of immunotherapy that makes your own immune cells better able to attack cancer. It is also called adoptive cell therapy, adoptive immunotherapy, and immune cell therapy.

Instead of giving you a drug, this treatment uses your own T cells — a type of immune cell — changed or selected in a lab to fight your cancer.

CAR T-cell therapy turns your own immune cells into better cancer fighters.

The basic steps

There are two main types of T-cell transfer therapy: TIL therapy and CAR T-cell therapy. Both share the same basic steps:

  1. Your own immune cells are collected.
  2. Large numbers of these cells are grown in the lab.
  3. The cells are given back to you through a needle in your vein.

Growing your T cells in the lab can take 2 to 8 weeks. During this time, you may have treatment with chemotherapy and maybe radiation therapy to get rid of other immune cells. Reducing your immune cells helps the transferred T cells work better. After these treatments, the lab-grown T cells are given back to you through a vein.

TIL therapy vs. CAR T-cell therapy

TIL therapy uses T cells called tumor-infiltrating lymphocytes that are found in your tumor. Doctors test these in the lab to find out which ones best recognize your tumor cells, then treat those selected cells so they grow to large numbers quickly. The idea is that these lymphocytes have already shown they can recognize your tumor, but there may not be enough of them — so giving you large numbers can help overcome that.

CAR T-cell therapy is similar to TIL therapy, but your T cells are changed in the lab so that they make a protein called CAR before they are grown and given back. CAR stands for chimeric antigen receptor. CARs are designed to let the T cells attach to specific proteins on the surface of cancer cells, improving their ability to attack.

Which cancers are treated

A TIL therapy called lifileucel has been approved by the FDA to treat melanoma. It has also shown promise in other cancers, such as certain cervical and bile duct cancers, but for those it is still experimental.

Several CAR T-cell therapies have been approved by the FDA for blood cancers. Ask your team which ones fit your cancer. CAR T-cell therapy has also been studied for solid tumors, including breast and brain cancers, but that use is still experimental.

Side effects to know about

T-cell transfer therapy can cause side effects that people experience in different ways. What you may have and how serious it is depends on how healthy you are before treatment, your type of cancer, how advanced it is, the type of therapy, and the dose. Doctors and nurses cannot know for sure when or if side effects will occur, so it is important to know which signs to look for.

Cytokine release syndrome. CAR T-cell therapy can cause this serious side effect. It happens when the transferred T cells, or other immune cells responding to them, release a large amount of cytokines into the blood. Cytokines are immune substances with many functions, and a sudden increase can cause fever, nausea, headache, rash, rapid heartbeat, low blood pressure, and trouble breathing. Most people have a mild form, but in some it can be severe or life-threatening.

Recognizing normal cells. Although CAR T cells are designed to recognize proteins found only on cancer cells, they can sometimes recognize normal cells too. Depending on which normal cells are affected, this can cause a range of side effects, including organ damage.

Capillary leak syndrome. TIL therapy can cause this syndrome, where fluid and proteins leak out of tiny blood vessels into surrounding tissues, causing dangerously low blood pressure. It may lead to multiple organ failure and shock.

Because serious side effects are possible, your team will monitor you closely and needs to hear about new symptoms right away.

When to get help sooner

Cytokine release syndrome often starts in the first days after your cells are given back. The FDA label for one CAR T product says to stay near a healthcare facility for at least 2 weeks and not to drive for at least 2 weeks. Ask your team what applies to you. If they give you a wallet card, carry it and show it to any clinician who sees you.

  • Call 911 or go to an emergency department if you struggle to breathe, your heart races, you feel faint, or someone notices you are confused, slurring your words, or hard to rouse. Take your wallet card if you have one.
  • Call your team now and go to an emergency department if your temperature reaches 100.4°F (38°C) or higher. After CAR T-cell therapy a fever is an emergency, not a wait-and-see symptom. Fever is a sign of cytokine release syndrome, and the FDA label says to get medical help right away for its signs. Say that you have had CAR T cells as soon as you arrive.
  • Call your care team right away if you get a new headache, a rash, sickness, or a pounding heartbeat in the weeks after your cells are given back. These can be signs of cytokine release syndrome.
  • Call your care team right away if you feel newly muddled over words, handwriting or simple tasks. Changes in thinking and speech can be nervous system side effects. For emergencies, call 911 or go to the ER.

Sources

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Common questions

What is CAR T-cell therapy?

CAR T-cell therapy is a type of T-cell transfer therapy, which is a kind of immunotherapy that makes your own immune cells better able to attack cancer. In CAR T-cell therapy, your T cells are changed in the lab so they make a protein called CAR (chimeric antigen receptor) that helps them attach to and attack cancer cells.

How does the process work?

Both TIL and CAR T-cell therapy involve collecting your own immune cells, growing large numbers of them in the lab, and then giving them back to you through a needle in your vein. Growing the cells can take 2 to 8 weeks.

Why might I have chemotherapy before getting my cells back?

While your T cells are being grown in the lab, you may have chemotherapy and sometimes radiation to get rid of other immune cells. Reducing your immune cells helps the transferred T cells work better. After this, the lab-grown T cells are given back through a vein.

What is the difference between TIL and CAR T-cell therapy?

TIL therapy uses tumor-infiltrating lymphocytes found in your tumor; doctors select the ones that best recognize your tumor and grow them in large numbers. CAR T-cell therapy is similar, but your T cells are changed in the lab to make a CAR protein that helps them attach to specific proteins on cancer cells.

What cancers are treated with these therapies?

A TIL therapy has been approved to treat melanoma. Several CAR T-cell therapies have been approved for blood cancers. CAR T-cell therapy has also been studied for solid tumors such as breast and brain cancers, but that use is still experimental.

What serious side effects can happen?

CAR T-cell therapy can cause cytokine release syndrome, from a large release of immune substances called cytokines. Most people have a mild form, but it can be severe or life-threatening. CAR T cells can also sometimes recognize normal cells, causing side effects including organ damage. TIL therapy can cause capillary leak syndrome.

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Written from National Cancer Institute material and compared with the source cited below.

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Sources last checked: 2026-08-13 what this meansLast updated: 2026-09-29Next planned review: 2027-01-14

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  1. Q1.According to this article, what does CAR T-cell therapy use to fight cancer?
  2. Q2.According to this article, how long can it take to grow the T cells in the lab?
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  4. Q4.According to this article, what serious side effect can CAR T-cell therapy cause?

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How this page was created

Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.

Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.

Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.

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