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DEAR MAYO CLINIC: What is chimeric antigen receptor T cell (CAR-T cell) therapy? How does it work to treat cancer, and who’s a good candidate for it?
ANSWER: CAR-T cell therapy uses white blood cells, called T cells, to fight cancer. It’s approved by the Food and Drug Administration to treat several kinds of blood cancer. CAR-T cell therapy typically is reserved for people with blood cancers where the disease has not responded to other cancer treatment.
White blood cells are part of the body’s immune system. T cells are a subtype of white blood cells. They combat threats to the body, such as infections and cancer. CAR-T cell therapy enhances the T cells’ natural cancer-fighting abilities, so they have a more powerful effect on cancer cells.
CAR-T cell therapy involves several steps. First, white blood cells are collected from a patient’s blood through a procedure called “leukapheresis.” Once the white blood cells have been collected, they are sent to a laboratory. There the T cells are modified genetically to strengthen their ability to kill cancer. That part of the process can take several weeks or more.
Before the CAR-T cells are returned to the patient, he or she usually has daily chemotherapy sessions for several days. The chemotherapy is used to make the immune environment in the body more favorable for CAR-T cells to stay alive and be active against the tumor. After that, the patient receives an infusion of the CAR-T cells. The infusion takes about 30 to 90 minutes in a process similar to a blood transfusion.
Once the CAR-T cells go back into the patient’s body, the cells become activated to kill cancer cells. The process of the CAR-T cells becoming activated can trigger significant side effects. Those side effects may include a high fever, fast heart rate, low blood pressure and low blood oxygen. After the infusion of the CAR-T cells, some patients also experience temporary neurologic effects, such as confusion, tremors and difficulty communicating.
Because of the potential side effects, patients may need care in the hospital for several days or more after CAR-T cell infusion, and some may require care in an ICU. After that, ongoing care and monitoring near the treatment facility typically is needed for four to six weeks. Due to the complexity of care associated with CAR-T cell therapy, it’s only offered at medical centers that can provide multidisciplinary specialty care.
Research has shown CAR-T cell therapy to be most effective in treating two types of blood cancers. The first is B cell acute leukemia in children and young adults up to age 25. The second is aggressive B cell non-Hodgkin lymphoma in adults. These are the only kinds of cancer that the FDA has approved for CAR-T cell therapy.
The treatment is not intended for someone who is newly diagnosed. Instead, it’s an alternative for those who already have gone through other more conventional cancer therapy, such as chemotherapy or immunotherapy, and that treatment has been unsuccessful.
A considerable amount of research is underway to see if CAR-T cell therapy could be appropriate as a treatment for different forms of cancer, too, including other blood cancers such as multiple myeloma. So if a patient has a type of cancer that hasn’t responded well to traditional treatment, it may be worthwhile to explore the possibility of enrolling in a clinical research trial that’s using CAR-T cell therapy.
Research at Mayo Clinic and other large academic medical centers also is exploring ways to better manage and reduce the side effects of this treatment, as well as assess the possibility of using CAR-T cell therapy in other diseases beyond cancer. — Dr. Yi Lin, Hematology, Mayo Clinic, Rochester, Minnesota