ABSTRACT
Pembrolizumab is an immune checkpoint inhibitor (ICPI), a type of immunotherapy that blocks the programmed death 1 (PD1) receptor expressed on T cells. In cancer, PD1 binds to its ligand, programmed death ligand 1 (PDL1), which is expressed by both innate immune cells and tumour cells and prevents T cells from killing cancer cells. Triple-negative breast cancer (TNBC) is characterised by a higher density of immune cell infiltrates, a higher expression of PDL1 and a higher tumour mutational burden than other breast cancer subtypes, making ICPI a promising treatment option in TNBC. 1 Furthermore, the use of anthracyclines, taxanes and platinum-based neoadjuvant chemotherapy is associated not only with improved pathological complete responses (pCRs) but also with increased PDL1 expression in tumour cells in TNBC. 2 The KEYNOTE-522 study investigated whether the combination of chemotherapy and ICPI improves clinical outcomes in this group of patients.
