AUTHOR=Wang Rong , Yang Yuchen , Ye Wei-Wu , Xiang Jianxing , Chen Songan , Zou Wei-Bin , Wang Xiao-Jia , Chen Tianhui , Cao Wen-Ming TITLE=Case Report: Significant Response to Immune Checkpoint Inhibitor Camrelizumab in a Heavily Pretreated Advanced ER+/HER2− Breast Cancer Patient With High Tumor Mutational Burden JOURNAL=Frontiers in Oncology VOLUME=10 YEAR=2021 URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2020.588080 DOI=10.3389/fonc.2020.588080 ISSN=2234-943X ABSTRACT=

Endocrine treatment plus CDK4/6 inhibitors have become standard of care for estrogen receptor positive (ER+) breast cancer. Although immune checkpoint inhibitors (ICIs) have shown promising antitumor activity in a variety of cancer types, only limited success has been achieved for metastatic breast cancer (mBC) patients, especially the ER+ subtype, which usually exhibit lower tumor mutation burden (TMB) compared with other subtypes and therefore perceived as immunologically quiescent. Here we present a case of an ER+/HER2- but TMB-high mBC patient who had significant response to combination therapy with anti-PD-1 antibody camrelizumab and vinorelbine and obtained partial response (PR) with a progression-free survival (PFS) of 5 months after failure of multiple lines of therapy. Our case indicates that TMB may serve as a potential biomarker in immunotherapy selection for normally immunologically “cold” tumors such as ER+ mBC, also molecular monitoring during the whole treatment course plays an important role in patient management.