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Heidi Chwan Ko,1,* RJ Seager,2,* Sarabjot Pabla,2 Maria-Fernanda Senosain,2 Erik Van Roey,2 Shuang Gao,2 Kyle C Strickland,1,3 Rebecca Ann Previs,1,4 Michelle F Green,1 Maureen Cooper,1 Mary K Nesline,1 Stephanie B Hastings,1 Kobina Agyaful Amoah,1 Shengle Zhang,2 Jeffrey M Conroy,2 Taylor J Jensen,1 Marcia Eisenberg,5 Brian Caveney,5 Eric A Severson,1 Shakti Ramkissoon,1,6 Shipra Gandhi7 1Labcorp Oncology, Durham, NC, USA; 2Labcorp Oncology, Buffalo, NY, USA; 3Department of Pathology, Duke University Medical Center, Duke Cancer Institute, Durham, NC, USA; 4Department of Obstetrics & Gynecology, Division of Gynecologic Oncology, Duke University Medical Center, Duke Cancer Institute, Durham, NC, USA; 5Labcorp, Burlington, NC, USA; 6Department of Pathology, Wake Forest Comprehensive Cancer Center, Wake Forest School of Medicine, Winston-Salem, NC, USA; 7Department of Hematology and Oncology, Roswell Park Comprehensive Cancer Center, Buffalo, NY, USA*These authors contributed equally to this workCorrespondence: Heidi Chwan Ko, Email Heidi.ko@labcorp.comBackground: The understanding of molecular characteristics of HER2-low breast cancer is evolving since the establishment of trastuzumab deruxtecan. Here, we explore the differences in expression patterns of immune-related genes in the tumor immune microenvironment (TME) and survival between HER2-low and HER2-zero breast cancers.Methods: Comprehensive genomic and immune profiling, including RNA-seq gene expression assessment of 395 immune genes, was performed on FFPE samples from 129 patients with advanced HER2-negative (immunohistochemistry (IHC) 0, 1+ or 2+ with negative ERBB2 amplification by in-situ hybridization) breast cancer. Both estrogen receptor (ER) and HER2 statuses were obtained from available pathology reports. mRNA expressions of immune biomarkers, except for PD-L1 IHC and TMB, were derived from RNA-seq. Statistical comparisons were performed using the Kruskal–Wallis or Wilcoxon Rank-Sum test or the two-sample test for equality of proportions with continuity correction (p≤ 0.05 for significance). Survival differences were calculated using Kaplan-Meier analysis (p≤ 0.05 for significance).Results: There were no significant differences in mRNA expressions of immune-related genes between HER2-low and HER2-zero breast cancers. However, HER2-low breast cancers were associated with a higher proportion of ER-positivity. When ER was analyzed along with HER2, we observed a significantly higher tumor immunogenic signature (TIGS) expression in HER2-zero/ER-negative tumors than in HER2-low/ER-positive tumors (p=0.0088). Similarly, lower expression of PD-L1 and T cell immunoglobulin and ITIM domain (TIGIT) mRNA was observed in HER2-low/ER-positive tumors when compared to HER2-zero/ER-negative tumors (p=0.014 and 0.012, respectively). Patients with HER2-low tumors had a longer median OS than those with HER2-zero tumors (94 months vs 42 months, p=0.0044).Conclusion: Patients with HER2-low breast cancer have longer survivals yet display no differences in immune-related gene expression when compared to those with HER2-zero cancers. The differences in survival can be attributed to the higher rate of ER-positivity seen in HER2-low breast cancers, compared to HER2-zero tumors.Keywords: HER2-low breast cancer, estrogen receptor, tumor immune microenvironment, immune checkpoint biomarkers, gene expression profiling, immune profiling |
