What are tumor-infiltrating lymphocytes?

Tumor-infiltrating lymphocytes (TILs) are immune cells made naturally by your body that find and attack cancer cells. These white blood cells constantly move through your blood and lymph system and look for diseased cells. They can recognize the unique markers on the surface of cancer cells, attacking and destroying them.

Sometimes, when cancer grows and spreads, it can affect the immune system, causing TILs to no longer work as they should.

Patient suffering from tumor-infiltrating lymphocytes sitting on the beach enjoying the sunset

What is TIL therapy?

TIL therapy is a type of immunotherapy, also called adoptive cellular therapy, that boosts the power of your immune system to attack specific types of cancer. As your cancer progresses and your TILs are no longer effective, TIL therapy can restart the cancer-fighting benefits of TIL cells in your body.

TIL therapy requires a specialized team and lab, and it’s currently only used after you’ve tried other treatment options. To create this therapy, your healthcare team will extract your own TIL cells and rapidly grow more of them in the lab. Then, this large number of new TIL cells is put back into your body to fight cancer more effectively.

Lab technician processing patient lymphocytes

How does TIL therapy work?

Tumor-infiltrating lymphocyte therapy works by giving you billions of additional TIL cells to fight cancer cells. To create these additional TIL cells, your care team takes existing ones directly from your tumor. This allows them to duplicate TIL cells that have already recognized targets on your cancer cells and started to attack them.

It takes about a month for the lab to grow your TIL cells. Then, you’ll have one week of high-dose chemotherapy before your new TIL cells are infused back into your body in the hospital. Often, TIL is a one-time treatment.

In addition to greatly increasing the number of TIL cells in your body as a form of therapy, research is ongoing to study how reengineering TIL cells in the lab could make them even more effective.

What cancers are treated with tumor-infiltrating lymphocytes?

Tumor-infiltrating lymphocytes are currently approved by the Food and Drug Administration (FDA) for treating advanced melanoma. When melanoma spreads or can’t be treated with other options, TIL therapy gives you another way to keep fighting the condition.

Researchers at Baylor Scott & White Health are also part of clinical trials evaluating new ways to use the power of tumor-infiltrating lymphocyte therapy for people with cancer. Across the nation, TIL therapy is being studied in clinical trials for several solid tumor cancers, including other types of skin cancer, non-small cell lung cancer, lung cancer, ovarian cancer, and head and neck cancer.

Doctor discussing tumor-infiltrating lymphocytes treatment with a patient

What is the treatment process for TIL therapy?

The entire treatment process for tumor-infiltrating lymphocyte therapy can take a few months. You’ll go through several steps to allow your care team to extract and grow TIL cells and to prepare your body for treatment. After treatment, your care team will monitor how well your therapy works.

Before your TIL therapy

To prepare for your TIL therapy, your care team will first need to extract existing TIL cells from your tumor and grow additional TIL cells in the lab.

  • First, you’ll have surgery, where your doctor will remove an area of your tumor. Generally, this is a minor procedure, and you can go home the same day.
  • In the lab, your care team will take TIL cells from the tissue of your tumor. Using special chemicals, these cells will be rapidly enhanced and multiplied—creating billions of TIL cells over about a month.
  • The cells are then frozen and sent to the hospital for treatment.
  • To prepare your body to receive the TIL cells, you will have a week of chemotherapy treatment before having your TIL infusion.

What are the possible side effects of TIL therapy?

Tumor-infiltrating lymphocyte therapy comes with a few possible side effects. And because TIL therapy requires chemotherapy before your infusion, you’ll have a weakened immune system during treatment. Your care team will work with you to manage any side effects that arise.   

Side effects may include:

  • Fever and chills
  • Dizziness or headaches
  • Shortness of breath
  • Nausea
  • Fatigue or weakness
  • Rash
  • Changes in your heart rate or blood pressure
  • Low blood counts

TIL therapy vs. CAR-T cell therapy

TIL therapy and CAR-T cell therapy are both types of immunotherapy that use your T cells to boost the ability of your immune system to fight cancer. These therapies give people another option when their cancer doesn’t respond well to other treatments. However, there are some differences in how these two treatments work and the types of cancer they treat.

TIL therapy

  • Extracts T cells directly from your tumor
  • Uses cells that attack multiple different targets on cancer cells
  • Multiplies a large number of cells in the lab and infuses them back into your body
  • Approved for solid tumors, such as melanoma


Chimeric antigen receptor (CAR)T-cell therapy

  • Uses T cells found in your blood
  • Modifies cells in the lab to recognize only one marker on cancer cells
  • Multiplies many cells in the lab and infuses them back into your body
  • Approved for blood cancers, such as leukemia, myeloma and lymphoma

We are a destination center for immune therapy in cancer care

With our team, you have the power of years of research, experience and innovation on your side. We bring together all the resources you need into one system to make accessing advanced treatments like immune therapy easier.

  • Following an 18-month process to become an authorized center, Baylor University Medical Center, part of Baylor Scott & White Health became one of the first in the nation to offer TIL therapy for advanced melanoma after it was FDA-approved in 2024.
  • In 2018, Baylor University Medical Center was one of the first North Texas providers to offer adult commercial use of CAR T-cell therapy to treat large B-cell lymphoma and acute lymphoblastic leukemia.
  • We have one of the nation’s largest networks of cancer centers accredited by the Commission on Cancer, which gives patients additional cancer resources and support services within their local communities.

Call 214.820.0111 to learn more

Ariel photo of Baylor University Medical Center, part of Baylor Scott & White Health

Clinical trials of new cellular therapies

While tumor-infiltrating lymphocyte therapy is only approved for a specific set of patients, clinical trials are underway to create even more cellular therapies for a range of cancer types.

Through our research at Baylor Scott & White Research Institute, our team is leading the way in developing the next generation of cancer treatments. Our robust research program—combined with a team of highly specialized providers—gives you access to clinical trials as part of your care.