Understanding CAR-T cell therapy and its potential side effects

By Mayo Clinic staff

Immunotherapy harnesses the body’s immune system to fight cancer. Chimeric antigen receptor-T cell therapy (CAR-T cell therapy) is a form of immunotherapy in which healthcare professionals remove a person’s T cells — white blood cells known as lymphocytes that are involved in the immune system response — and genetically modify them to produce chimeric antigen receptors (CARs). These CAR-T cells are then infused back into the patient's bloodstream, where they target and kill cancer cells.

"CAR-T cell therapy is among the most promising areas of cancer treatment, with many success stories worldwide," says Mohamed Kharfan Dabaja, M.D., a hematologist and oncologist at Mayo Clinic. "It has given new hope to patients who previously had limited options."

Who is eligible for CAR-T cell therapy?

The Federal Drug Administration has approved CAR-T cell therapy to treat these blood cancers:

• Adult and pediatric B-cell precursor acute lymphoblastic leukemia (ALL)
• Diffuse large B-cell lymphoma (DLBCL)
• Primary mediastinal large B-cell lymphoma
• Large B-cell lymphoma transformed from follicular lymphoma
• High-grade B-cell lymphoma
• Aggressive B-cell lymphoma not otherwise specified (NOS)
• Mantle cell lymphoma
• Follicular lymphoma
• Multiple myeloma

People with these diagnoses whose disease has not responded to treatment (refractory) or whose disease has relapsed may be eligible for CAR-T cell therapy. Patients must undergo a thorough evaluation to determine if CAR-T cell therapy is the best treatment option.

How long does it take to complete CAR-T cell therapy?

The CAR-T cell therapy process is complex and can take several weeks. Most people have a reaction to CAR-T cells that may require them to stay in the hospital for monitoring and management.

"People who plan to receive CAR-T cell therapy should expect to stay in the hospital after infusing the cells for several days so their care team can monitor their response to therapy," says Dr. Kharfan Dabaja.

Review these infographics to learn more about the CAR-T cell therapy process:

• "CAR-Tell Cell Therapy – A new approach in the fight against cancer"
• "Mayo Clinic CAR-T Cell Therapy Program – Treatment overview"

What are the possible side effects of CAR-T Cell Therapy?

While the side effects of CAR-T therapy are generally reversible, Dr. Kharfan Dabaja says they may include:

• Cytokine release syndrome (CRS): CRS is one of the most common side effects of CAR-T cell therapy, and it's triggered by the immune response that occurs when modified T-cells are introduced into a patient's bloodstream. As the T-cells start targeting cancer cells, they release a large number of cytokines — proteins that can cause the immune system to overreact. This can lead to fever, low blood pressure, muscle pain and other flu-like symptoms. In severe cases, CRS can cause organ failure and even be fatal. Most CRS-related symptoms can be managed with medications and close monitoring.
• Neurotoxicity: Some patients may experience a neurologic effect known as neurotoxicity after receiving CAR-T cell therapy. This is a potentially dangerous condition in which the immune response to the treatment affects the central nervous system. While the exact cause of neurotoxicity is not well understood, some studies suggest that it is partly related to the severity of CRS. Symptoms can include confusion, seizures and difficulty speaking or walking. With close monitoring, most cases of neurotoxicity are resolved without long-term side effects.
• Blood disorders: CAR-T cell therapy can result in blood changes that can lead to anemia, thrombocytopenia (low platelet count) and other blood disorders. These effects are generally short-lived and resolve themselves over time, but they can be more severe in some patients.
• Infections: People who receive CAR-T cell therapy may be at increased risk for infections, especially during the first few weeks after treatment when the immune system works overtime to fight the cancer. People with low white blood counts could remain at increased risk of infections for some time. They should be closely monitored for signs of infection, including fever, chills and a general feeling of being unwell.
• Long-term side effects: As CAR-T cell therapy is still relatively new, healthcare professionals don’t yet know the full spectrum of its long-term side effects.

Dr. Kharfan Dabaja encourages people considering CAR-T cell therapy to talk to their care teams about the potential risks and benefits and any concerns about their long-term health. He also recommends seeking evaluation for CAR-T cell therapy at a comprehensive cancer center.

"If you believe you or a loved one may be a candidate for this therapy, it’s best to connect with a care team that has experience treating many cancer patients with CAR-T," he says.

Learn more

Learn about the CAR-T Cell Therapy Program at Mayo Clinic.

Read about CAR-T cell therapy research at Mayo Clinic and find a CAR-T cell therapy clinical trial.

Read CAR-T cell therapy patient stories:

• "CAR-T cell therapy restores hope for leukemia patient"
• "'She has big things ahead of her.' CAR-T cell therapy gives Florida teen hope"

Join the CAR-T Cell Therapy Support Group on Mayo Clinic Connect.