Tumor-infiltrating lymphocytes therapy (often abbreviated as TIL therapy) is a form of immunotherapy (the category of cancer treatments that use your own immune system to attack and kill cancer cells). TIL cancer therapy boosts your body's natural immune response to improve your ability to fight cancer.

How Does TIL Cell Therapy Work?

Doctors take a sample from one of your tumors and extract immune cells called tumor-infiltrating lymphocytes (TILs) that have already entered the tumor to fight it. Your body produces TILs as a response to cancer. They are specially built to fight your specific cancer.

Once the TILs are collected, they're sent to a lab where they're multiplied until there are huge numbers (often billions) of them. Next, doctors prepare your body for the TIL treatment with a round of chemotherapy. Once you're ready, the TILs are put back into your body with an infusion and you're given an immune-boosting therapy called interleukin 2 (IL-2). The TILs will then naturally go where the cancer is and attack it.

What Is the Success Rate of TIL Therapy?

TIL treatments are new and still largely experimental, but results are promising. A 2023 study showed a 49% overall response rate with 20% of patients experiencing complete remission.

What Kinds of Tumors Are Treated with TILs?

Tumor-infiltrating lymphocytes are an FDA-approved treatment for metastatic melanoma that is resistant to other treatments. They show promise in treating other kinds of solid tumors. TIL therapy has been used through clinical trials to treat lung cancer and genitourinary cancers, among others. The list of cancers that may be treated with TIL therapy is growing as clinical trials continue and scientists develop the technique further.

Learn more about TIL therapy for melanoma.

What Are the Disadvantages of Tumor-Infiltrating Lymphocytes?

TIL therapy carries very few side effects. In general, the side effects result from the other components of the treatment (chemotherapy and IL-2) rather than the TILs themselves and include fever or chills, nausea, fatigue, and other typical symptoms of chemotherapy.

What Are the Advantages of Tumor-Infiltrating Lymphocytes?

TIL therapy is an exciting treatment because it can attack cancer cells throughout the body and can be effective in treating metastatic cancer. Unlike some other forms of immunotherapy, TIL treatment is "polyclonal," which means it can target many different tumor antigens.

What Is the Difference Between Tumor-Infiltrating Lymphocytes and CAR T-Cell Therapy?

There are a few key differences between these two types of immunotherapy. Both treatments collect and boost your body's T-cells to improve your immune response to cancer. However, in TIL therapy, the treatment is polyclonal (can target many cancer antigens), while CAR T-cell treatments are monoclonal (targeting one specific antigen). The other key difference is that in TIL therapy, the T-cells don't need to be genetically modified, while in CAR T-cell therapy, they do.