Comprehensive Assessment of Immune Phenotype and Its Effects on Survival Outcomes in HER2-Low versus HER2-Zero Breast Cancer

In this study, investigators evaluated the immune-related gene expression patterns from real-world CGIP data from 129 patients with advanced breast cancer during standard-of-care treatment.  There were no significant differences in immune gene expressions such as PD-L1, TIM-3, LAG-3, and TIGIT between HER2-low and HER2-zero breast cancers. HER2-low breast cancers were associated with a higher proportion of estrogen receptor (ER)-positivity. Patients with HER2-low breast cancer have a longer median overall survival than those with HER2-zero cancer, suggesting that there is a prognostic difference between the two, primarily driven by ER expression.