Tumour infiltrating lymphocytes

October 17, 2023

Tumour infiltrating lymphocytes (TILs) are a type of immune cell that has moved from the bloodstream into a tumour. They are a component of the body’s immune response, which aims to identify and attack cancer cells. Immune checkpoint inhibitors (such as PD-L1 inhibitors) prevent cancer cells from blocking the natural activity of tumour infiltrating lymphocytes.

Why are tumour infiltrating lymphocytes important?

• Immune response indicator: The presence of tumour infiltrating lymphocytes in a tumor often indicates that the immune system recognizes the tumor as a threat and is attempting to fight it. This can be a positive sign in terms of prognosis.
• Prognostic value: High levels of tumour infiltrating lymphocytes are generally associated with better outcomes in several types of cancers. They can indicate a more favorable prognosis and a better response to certain treatments, including immunotherapy.
• Predictive marker for therapy: The presence and density of tumour infiltrating lymphocytes can help predict how well a patient will respond to immunotherapies. Tumors with high levels of these cells are more likely to respond to treatments that boost the immune system’s ability to attack cancer cells.
• Role in cancer therapy: Tumour infiltrating lymphocytes can be harvested, expanded, and reinfused into patients as a form of adoptive cell transfer therapy. This technique has shown promise in treating certain cancers, particularly melanoma.

Types of tumors associated with tumour infiltrating lymphocytes

Tumour infiltrating lymphocytes are found in various types of tumours, with their presence being particularly significant in the following cancers:

• Melanoma: Melanoma has been extensively studied for its association with tumour infiltrating lymphocytes. High levels are linked to better survival rates and a favorable response to immunotherapy.
• Breast cancer: In certain subtypes of breast cancer, particularly triple-negative and HER2-positive breast cancers, the presence of tumour infiltrating lymphocytes is associated with better outcomes and improved responses to chemotherapy and immunotherapy.
• Lung cancer: Non-small cell lung cancer (NSCLC) shows a positive correlation between tumour infiltrating lymphocytes and patient outcomes. The level can be predictive of response to immune checkpoint inhibitors.
• Ovarian cancer: The presence of tumour infiltrating lymphocytes in ovarian cancer is linked to improved survival rates, suggesting that an active immune response is beneficial in this type of cancer.
• Colorectal cancer: Tumour infiltrating lymphocytes in colorectal cancer, especially those within the microsatellite instability-high (MSI-H) subtype, are associated with a better prognosis and responsiveness to immunotherapy.
• Head and neck cancers: These cancers also show a positive correlation between tumour infiltrating lymphocytes and patient survival and response to treatments.
• Bladder cancer: The presence of tumour infiltrating lymphocytes is associated with better responses to immunotherapy, particularly in advanced stages of bladder cancer.

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