PD-L1 Testing in Patients with Breast Cancer: Controversies and Current Practice

Atezolizumab has emerged as a novel treatment in patients with triple-negative breast cancer showing unprecedented survival gain. This breakthrough benefit is exclusively observed in PD-L1-positive patients, but PD-L1 positivity still lacks a reliable definition. In this review, we discuss the current data on PD-L1 testing and its impact on the treatment of patients. The VENTANA SP142 assay was used in the trial that led to the approval of...