Tumour-infiltrating Lymphocytes and Radiation Therapy in Rectal Cancer: Systematic Review and Meta-analysis

Area of Science:

• Immunology
• Oncology
• Radiotherapy Research

Background:

• Tumour-infiltrating lymphocytes (TILs) are recognized as significant cancer biomarkers.
• Specific TIL subtypes (CD8+, CD4+, CD3+, FOXP3+) have demonstrated associations with patient prognoses.
• Limited data exist on the prognostic value of TILs in patients undergoing radiation therapy (RT).

Purpose of the Study:

• To systematically review and meta-analyze existing data on the utility of TILs as biomarkers for patients receiving curative-intent RT.
• To evaluate the association between TILs and treatment response or survival outcomes in this patient population.

Main Methods:

• A systematic literature search was conducted across major databases (PubMed, EMBASE, Cochrane, Web of Science).
• Studies were screened for eligibility based on predefined criteria, including curative-intent RT and reported TIL-outcome relationships.
• Quality assessment and risk of bias evaluation followed PRISMA guidelines, with data grouped by TIL type, timing of assessment (pre- or post-RT), and clinical outcome.

Main Results:

• Thirty-one studies met the quality criteria, with a focus on rectal cancer (20 studies).
• Pre-RT CD8+ and FOXP3+ TILs were significantly associated with disease-free survival and overall survival.
• Post-RT CD8+ TILs were linked to disease-free survival and overall survival, while preoperative TILs generally correlated with RT response.

Conclusions:

• TILs serve as a valuable prognostic parameter for tumour response and survival in patients receiving RT for rectal cancer.
• Standardization of TIL measurement techniques is crucial for future research and clinical application.
• Further studies are needed to establish clear clinical protocols for utilizing TILs in RT decision-making.