Tumor Infiltrating Lymphocyte Therapy and Its Side Effects
Tumor infiltrating lymphocyte (TILs) therapy or tumor-derived autologous T cell immunotherapy is a form of immunotherapy that uses your body’s own immune cells to target and destroy cancer. It involves growing and reintroducing special immune cells taken directly from your tumor. TILs therapy can be very helpful in treating some types of solid tumor cancers, such as melanoma, even when other treatments are no longer working.
What are tumor-infiltrating lymphocytes (TILs)?
Tumor-infiltrating lymphocytes (TILs) are a part of the immune system. They are specific types of white blood cells (lymphocytes) that have left the bloodstream and entered (infiltrated) a tumor to attack the cancer cells. Once TILs get inside the tumor, they can find different targets on the cancer cells and destroy them.
What is TILs therapy and how does it work?
TILs therapy helps your immune system fight cancer by using your own tumor-infiltrating lymphocytes (TILs). These cells are collected from your tumor, multiplied in a lab, and then returned to your body in large numbers to help target and destroy cancer cells.
To understand how TILs therapy can help treat cancer, it helps to know how the immune system works to find foreign or harmful substances like germs or cancer cells.
How immune receptors and foreign antigens interact
The immune system recognizes foreign substances by looking for antigens – proteins on the surface of those cells. Immune cells called lymphocytes (T cells and B cells) have their own proteins called receptors that attach to these antigens and help trigger other parts of the immune system to destroy the foreign substance.
The relationship between antigens and immune receptors is like a lock and key. Just as a lock can only be opened with the right key, each foreign antigen has a unique immune receptor that can bind to it.
Cancer cells also have antigens, but if your immune cells don't have the right receptors, they can't attach to the antigens and help destroy the cancer cells.
How TILs therapy boosts your immune response
For TILs therapy, a piece of your tumor is removed and analyzed in a cell therapy lab to find the lymphocytes (TILs) that have naturally found and entered the tumor, showing they carry the right receptors to recognize the antigens on your cancer cells. The TILs are carefully tested to choose the ones that respond most strongly to your cancer cells. These are then multiplied in the lab and given back to you in large numbers to help your immune system kill the cancer cells.
What is the difference between TILs therapy and CAR T-cell therapy?
TILs therapy and CAR (chimeric antigen receptor) T-cell therapy are both cellular therapies that stimulate your immune system to find and attack cancer cells. However, there are differences:
- TILs are used to treat solid tumors, while CAR T cells are used to treat blood cancers like lymphoma, leukemia, and multiple myeloma.
- TILs are collected directly from the tumor, while CAR T cells are collected from the bloodstream.
- TILs can already recognize the cancer cells, so no special changes must be made to the cells once they are removed. CAR T cells must be modified in the lab to recognize and attack the cancer cells.
- TILs therapy is polyclonal, meaning it can attack many different antigens in the cancer cells, while CAR T cell therapy is monoclonal, meaning it targets one specific cancer antigen.
Which cancers can be treated with TILs therapy?
One type of TILs therapy called Lifileucel (Amtagvi) is approved by the US Food and Drug Administration (FDA) to treat melanoma that has spread to other parts of the body. TILs therapy is typically used after other types of treatment have been tried.
Many other TILs therapies (and similar types of treatment) are now being studied in clinical trials, in the hope of treating other types of solid tumors such as lung, cervical, and genitourinary cancers.
Getting TILs therapy
Getting TILs therapy is quite different from other types of immunotherapy treatment. It involves:
- Surgery to remove a piece of the tumor
- Waiting several weeks for the TILs to be identified and multiplied in the lab
- Getting the TILs infusion and being monitored closely, sometimes in the hospital for 1-2 weeks
Collecting and growing the TILs
First, a part of your tumor is removed during surgery. It is sent to a special lab where the lymphocytes are separated out from the other cells. The TILs are identified and then stimulated to grow to large numbers over a period of several weeks.
Receiving the TILs infusion
Once enough TILs have grown, steps will be taken to get you ready to receive them.
A few days before the TILs infusion, you will likely be given chemotherapy to help lower the number of other immune cells in your body. This helps the body accept the TILs. This may be done in the hospital or in the clinic, depending on the center.
Following a few days of “rest,” you’ll be admitted to the hospital to receive the TILs infusion (through an IV) into your blood. This usually takes a few hours.After getting the TILs, you may also be given a type of immunotherapy called interleukin-2 (IL-2), which will help the TILs attack the cancer. This is usually done several hours after the TIL infusion and may be repeated over several days. You’ll be monitored closely for any signs of a reaction during this time and for several days afterwards. Sometimes you’ll need to stay in the hospital for a few weeks before going home.
For several weeks, you’ll need to get regular checks at the hospital or clinic. This will help your doctor identify any problems or reactions to the therapy as soon as possible.
Side effects of TILs therapy
TILs therapy can be very effective against some hard-to-treat cancers, but it can also sometimes cause serious or even life-threatening side effects. Because of this, it needs to be given in a medical center that is specially trained in its use, and you will need to be watched closely for several weeks after getting the TILs cells.
Serious side effects can include:
- Very low blood cell counts, which can increase the risk of serious bleeding and infections
- Internal bleeding
- Serious infections
- Heart problems
- Lung problems
- Kidney problems
- Infusion reactions
TILs therapy can also cause capillary leak syndrome that causes proteins and fluid to leak out of small blood vessels (capillaries) into the tissue. This can cause a decrease in blood pressure and if it worsens, can lead to organ failure.
If you are getting TILs therapy, it’s very important to report any side effects to your health care team right away, as there are often medicines that can help treat them.
How is TILs therapy paid for?
TILs therapy is expensive. The cost of the TILs cells alone is around $500,000 because of the complexity of how the TILs are collected and made. This doesn’t include the costs of hospital admission, surgery needed to collect the specimen used to identify the TILs, tests, procedures, and other expenses which can lead to the total cost being well over $500,000. While Medicare and some commercial insurances do cover some of the costs of TILs therapy, they usually don’t cover the full amount. The amount of coverage also varies between commercial plans. Medicaid coverage also varies and depends on your state of residence.
Before starting TILs therapy, your care team will work with your insurance company to check what your policy covers. You will want to ask questions to learn as much as possible about the costs of cancer treatment. Be sure to talk with them about out-of-pocket costs including deductibles, co-payments as well as other medication costs. The TILs center will also likely have a social worker, nurse navigator or financial coordinator to help with this process. They can talk with you about programs to help with expenses and help you access resources in your local community.
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- References
Developed by the 91黑料不打烊 medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
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Last Revised: July 7, 2025
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