AUTHOR=Brasó-Maristany Fara , Sansó Miriam , Chic Nuria , Martínez Débora , González-Farré Blanca , Sanfeliu Esther , Ghiglione Lucio , Carcelero Esther , Garcia-Corbacho Javier , Sánchez Marcelo , Soy Dolors , Jares Pedro , Peg Vicente , Saura Cristina , Muñoz Montserrat , Prat Aleix , Vivancos Ana TITLE=Case Report: A Case Study Documenting the Activity of Atezolizumab in a PD-L1-Negative Triple-Negative Breast Cancer JOURNAL=Frontiers in Oncology VOLUME=11 YEAR=2021 URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2021.710596 DOI=10.3389/fonc.2021.710596 ISSN=2234-943X ABSTRACT=

The immune checkpoint inhibitor atezolizumab is approved for PD-L1-positive triple-negative breast cancer (TNBC). However, no activity of atezolizumab in PD-L1-negative TNBC has been reported to date. Here, we present the case study of a woman with TNBC with low tumor infiltrating lymphocytes and PD-L1-negative disease, which achieved a significant response to atezolizumab monotherapy and durable response after the combination of atezolizumab and nab-paclitaxel. The comprehensive genomic analysis that we performed in her tumor and plasma samples revealed high tumor mutational burden (TMB), presence of the APOBEC genetic signatures, high expression of the tumor inflammation signature, and a HER2-enriched subtype by the PAM50 assay. Some of these biomarkers have been shown to independently predict response to immunotherapy in other tumors and may explain the durable response in our patient. Our work warrants further translational studies to identify biomarkers of response to immune checkpoint inhibitors in TNBC beyond PD-L1 expression and to better select patients that will benefit from immunotherapy.