Pembrolizumab and atezolizumab in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is defined by a lack of expression of both estrogen (ER) and progesterone (PgR) receptors as well as human epidermal growth factor receptor 2 (HER2) and is associated with poor prognosis. Moreover, the systemic treatment options are limited. However, the TNBC is more likely than other breast cancer subtypes to benefit from immune checkpoint blockade therapy due to its higher immunogenicity, higher enrichment by tumour-infiltrating lymphocytes (TILs), and higher levels of programmed cell death ligand 1 (PD-L1) expression. Thus far, atezolizumab was approved in combination with nab-paclitaxel for patients with unresectable locally advanced or metastatic TNBC whose tumours express PD-L1. Currently, it seems that PD-L1-positive subgroup will potentially benefit the most from the immune checkpoint inhibitor (ICI) treatment. Moreover, it seems that better results are seen when an ICI is given as first-line treatment than when an ICI is given in later lines of treatment for advanced TNBC/metastatic TNBC. Recently, pembrolizumab has demonstrated promising results in early-stage TNBC what can lead in near future to its approval in (neo)adjuvant setting. This review summarizes the development and highlights recent advances of the atezolizumab and pembrolizumab in early and advanced/metastatic TNBC.