Real‐world prevalence of PD ‐ L1 positivity in early‐stage/metastatic triple‐negative breast cancer: primary results and pathology insights from the global retrospective observational VANESSA study

AIM: To understand whether the worldwide implementation of PD-L1 testing in triple-negative breast cancer (TNBC) can be achieved in routine clinical practice. METHODS AND RESULTS: The multicentre retrospective observational VANESSA study consecutively and uniformly enrolled patients treated with systemic therapy for early or metastatic (e/m)TNBC diagnosed between 2014 and 2017. PD-L1 status was retrospectively assessed locally and centrally using the VENTANA PD-L1 (SP142) Assay (PD-L1 expression on tumour-infiltrating immune cells covering ≥1% of the tumour area). The primary objective was to determine the prevalence of PD-L1 positivity assessed locally on primary and/or metastatic tumour tissue. Concordance between local and central testing was a secondary endpoint. PD-L1-positive prevalence was 38% in eTNBC (728/1902) and 20% in mTNBC (30/152) and was higher in submitted tissue size >5 versus