Gene expression profiles of PD-L1 SP142 expression in triple-negative breast cancer

The SP142 PD-L1 assay is a companion diagnostic for atezolizumab in metastatic triple-negative breast cancer (TNBC). The VENTANA SP142 assay was used to identify PD-L1 expression from TMA slides where PD-L1-positivity for an individual sample was defined as ≥1% of tumor-infiltrating immune cells as having PD-L1 expression. The PD-L1-positive gene signature consisted of 94 immune-related genes. The PD-L1-positive signature was predictive of pathologic complete response and survival outcome in multiple TNBC cohorts. In other malignancies treated with ICIs, the PD-L1-positive signature was associated with response and improved survival. We prospectively collected tumor tissues from specimens of surgically resected breast cancer at the Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea, between July 1997 and December 2007. A total of 82 patients with triple negative breast cancer were enrolled for gene expression profiling.