Refining Patient Selection for Breast Cancer Immunotherapy: Beyond PD-L1

An intense quest is ongoing for complementary tumour- or host-related predictive biomarkers in breast immuno-oncology. Among the upcoming biomarkers, quantity, immunophenotype and spatial distribution of tumour-infiltrating lymphocytes and other tumour microenvironment cells as well as immune gene signatures emerge as most promising and are being increasingly tested in clinical trials.