Tumour-infiltrating lymphocytes and breast radiotherapy: perspectives from the International Immuno-Oncology...

Tumour-infiltrating lymphocytes (TILs) are prognostic and predictive biomarkers in breast cancer. High pre-treatment TILs are associated with a favourable prognosis and improved response to systemic therapies. However, the role of TILs in mediating response to radiotherapy in breast cancer remains underexplored, with scarce clinical evidence to date. In this Review, we present an overview of current evidence and potential mechanisms, highlight opportunities for integrating TILs into radiation oncology trials and clinical practice, and call for standardised TIL reporting to accelerate biomarker-driven individualisation of radiotherapy in breast cancer.