Connecting Single-cell Immune Profiling in Peripheral Blood with Intratumoral T Cell Expansion in Breast Cancer Upon Checkpoint Immunotherapy

In Belgium, breast cancer is the most common cancer in the female population. Although the immune system is equipped with tumor-killing properties, cancerous cells employ evasion techniques, which can be countered using immune checkpoint blockade (ICB) therapy. Nevertheless, only a subset of patients derives clinical benefit from ICB. It has been shown that patients who respond to ICB exhibit T cell expansion in the tumor. However, to determine this in a clinical routine setting, multiple tumor biopsies are necessary, which is not feasible. Therefore, it is important to identify non-invasive biomarkers, found in peripheral blood, to accurately and safely predict and monitor a patient’s therapeutic benefit. Innovative single-cell technologies will be applied on paired pre- and on-treatment peripheral blood mononuclear cells (PBMC) from breast cancer patients to identify non-invasive biomarkers and to improve our understanding of circulating immune cells in cancer.