Tumor-Infiltrating Lymphocytes (TIL) Therapy

October 24, 2024

This page was reviewed under our medical and editorial policy by Alexis Boling, MSN-RN, CNML, director, nursing, Immune Effector Cell & Gene Therapy Program, City of Hope^® Cancer Center Duarte

Immunotherapy is a treatment that helps the body’s own immune system fight cancer. It includes a growing field called adoptive cell therapies in which a patient’s own immune cells are altered in a laboratory to improve their ability to target and destroy cancer cells. 

One of these personalized immune system treatments is known as tumor-infiltrating lymphocyte (TIL) therapy. As its name suggests, TIL therapy is formulated to target and treat an individual’s solid cancer tumors. The U.S. Food and Drug Administration approved the first TIL therapy in 2024 for the treatment of advanced melanoma (skin cancer), called lifileucel (Amtagvi^TM).

TIL therapy research is ongoing, and tumor-infiltrating lymphocytes have also shown promise in fighting tumor cells in other cancers, such as breast, colorectal, bile duct and ovarian cancers, as well as cervical squamous cell carcinoma.

What Are Tumor-Infiltrating Lymphocytes?

Lymphocytes are immune cells made in the bone marrow and found in a person’s lymph tissue and blood. They include T lymphocytes that destroy cancer cells and B lymphocytes that make antibodies (substances that help destroy the antigens found on cancer cells). Both T cells and B cells are types of white blood cells.

When lymphocytes migrate out of the blood and lymph tissue and into tumors, they are known as tumor-infiltrating lymphocytes, or TIL.

Because TIL cells identify and destroy cancer cells in tumors, they are used in TIL therapy. During this treatment, TIL cells are removed from a patient’s tumor through a biopsy. These cells are then grown in large quantities in a laboratory and finally returned to the patient’s body. The expanded quantity of these cancer-fighting cells is meant to better equip the person’s immune system to destroy cancer tumors.

How Does TIL Therapy Work?

Targets on cancer cells called antigens produce immune system responses. While other types of adoptive cell therapies (such as chimeric antigen receptor T cell therapies) program immune cells to identify and attach to specific antigen targets in order to destroy cancer cells, TIL cells already have tumor-specific antigen recognition. This means they recognize cancer cell antigen targets without needing to be programmed to find and attack them.

Doctors perform lab tests on TIL cells that have been removed from a patient’s tumor in order to discover which will more successfully target their cancer cell antigens. These are then separated from the other TIL cells and coated in substances to help them grow quickly. The growing process takes about two to eight weeks.

Since the lab-grown TIL immune cells are considered more successful at destroying the person’s cancer tumor, chemotherapy will be administered beforehand to destroy other immune cells that may get in the way of the newly cloned TIL cells.

These new TIL cells are then put into the person’s body via an intravenous (IV) infusion. The patient might also be given therapy such as interleukin-2 to boost his or her immune system activity. This helps the newly returned TIL cells attack the cancer.

In some cases, doctors may choose to further enhance a patient’s TIL cells while they are still in the laboratory by engineering them for certain characteristics, such as an upgraded ability to return to the tumor site after being infused back into the body.

How Many TIL Therapy Treatments Are Typical?

Since TIL cells are a natural part of the body and are not excreted out like most medications, TIL therapy usually consists of a one-time infusion treatment. Patients will likely be hospitalized during the treatment so they may be monitored for any side effects. They may also be given medication to boost their immune system before being released to go home.

Side Effects of Tumor-Infiltrating Lymphocyte Therapy

Side effects of TIL therapy may be due to either the therapy itself, the chemotherapy given before the infusion or to the interleukin-2 given afterward. The most common side effects may include:

• High fever
• Anemia
• Low platelet counts
• Low white blood cell counts

Patients may also experience chills or fever, fatigue, diarrhea, low blood pressure and skin rashes.

Sometimes patients have other, more serious side effects, which may include:

• Heart, lung or kidney problems
• Internal bleeding
• Severe infections

It is important for patients to reach out to their doctor right away if any of these or other side effects develop, as they may be life-threatening. The care team will work to diagnose any potential underlying health issues and provide appropriate treatments to aid in recovery after TIL therapy.

Tumor Infiltrating Lymphocyte Therapy at City of Hope

Scientists at City of Hope are at the forefront of TIL therapy innovations and clinical trials, and we’re among the few cancer centers to currently offer TIL therapy. Our researchers are constantly evaluating new options and improving the efficacy of existing tumor infiltrating lymphocyte therapies to develop more powerful treatments for cancer and other diseases.

Learn more about our TIL therapy research