Tumor infiltrating lymphocyte (TIL) therapy is a type of immunotherapy that uses your body’s own cells to fight cancer. TIL (pronounced till) is a promising treatment for some types of solid tumors, especially melanoma. 

Researchers at Memorial Sloan Kettering Cancer Center (MSK) are studying TIL therapy in clinical trials, also known as research studies. They hope to learn the best way to use this treatment and who it may help. 

What are tumor infiltrating lymphocytes (TILs)? 

Lymphocytes (LIM-foh-sites) are a type of white blood cell. They’re an important part of your immune system. They help your body fight infections and diseases, including cancer. 

Tumor infiltrating lymphocytes come from the tumor. Infiltrating (IN-fil-trey-ting) means to enter, and these lymphocytes are found inside the tumor.   

The first step in TIL therapy is surgery to remove the tumor. Next, we separate the lymphocytes from the rest of the tumor cells. We send these lymphocytes to a laboratory where they’re isolated (separated from other types of cells) and grown in larger numbers. 

How does TIL therapy work? 

All types of immunotherapy use the body’s own immune system to fight cancer. Some immune cells have a natural ability to spot and attack tumors.  

TIL therapy uses the lymphocytes’ power to get inside a tumor and attack it. With TIL therapy, we improve these cells and grow more of them. This treatment may give the immune system a better chance of fighting cancer. 

The TIL approach can work well for people with cancer that has metastasized (spread) to many parts of the body.  

Doctors need to remove at least one tumor to collect the TIL cells. Then, they put the TILs back in the body. These TIL cells can find and kill tumors anywhere in the body. They can even kill tumors that cannot be removed by surgery. 

How is TIL therapy different from other cellular therapies? 

TIL therapy is like another therapy that uses a person’s own immune cells, called chimeric antigen receptor (CAR) T cell therapy. With CAR T therapy, your own T cells are changed in a laboratory. They’re made to recognize a specific protein, known as a marker, that’s on the surface of blood cells with cancer.  

TIL therapy may work better against solid tumors. That’s because these immune cells can recognize more of the markers that are found most often inside solid tumors. Unlike CAR-T cells, TILs often target multiple proteins, but the targets are not known ahead of time. 

What kinds of cancers can TIL therapy treat? 

TIL therapy is approved by the U.S. Food and Drug Administration (FDA) to treat melanoma that has spread and that does not respond to other treatments. MSK has clinical trials that use TIL therapy to treat some subtypes of melanoma. They include uveal (eye) melanoma and melanoma that has spread to the brain. 

Researchers at MSK and other hospitals are studying TIL therapy for other types of solid tumors as well, including lung cancer. Researchers believe TIL therapy may one day prove to be a good treatment for many types of solid tumors. 

What is it like to get TIL therapy? 

The first step of TIL therapy is surgery to remove the tumor and collect its TIL cells. The tumor can be the primary tumor (where cancer started) or a tumor that spreads to another area.  

Most often, your surgeon will choose the tumor that’s easiest to remove. This will let you recover from the surgery faster so you’re ready to start the next part of the treatment. 

The TILs will be grown in the lab, which takes several weeks. Once experts confirm the cells have grown successfully, you will have chemotherapy to get your body ready for the TIL therapy. Chemotherapy affects some parts of the immune system. It improves the chances that the TILs will survive and multiply when they’re put back into your body.

When the TIL cells are ready, they will be infused into your bloodstream through a port in your chest. An infusion is a method of putting something into the body. The cells will then circulate (move) throughout your body and hunt down more tumors. 

You may be given more drugs to stimulate your immune system after the TIL infusion. They can help the TIL cells to work even better. 

What are the side effects of TIL therapy? 

You will need to stay in the hospital for at least two weeks to receive TIL therapy. One reason is because your immune system is weaker from the chemotherapy you had before the TIL infusion. This makes it more likely you can get infections. 

The TIL therapy also has other side effects, and some of them are like the ones people have after CAR T therapy. Others are caused by the drugs used to stimulate your immune system 

Side effects of TIL therapy can include: 

• High fevers and chills
• Nausea and loss of appetite
• Headaches, dizziness, and other issues that affect the nervous system
• Feeling very tired and weak
• Low blood counts 
• A buildup of fluids in your body, which can put stress on your heart and lungs

MSK has been treating people with different forms of cellular therapy for many years. We have medical experts from many areas who have experience in treating these side effects.