Hence, Trastuzumab deruxtecan has shown significant anti-tumor activity in several HER2-expressing cancers, including HER2-positive and HER2-low breast cancer, HER2-positive gastric cancer, and NSCLC with HER-2-activating mutations, regardless of Her2 protein expression and HER2-overexpressing colorectal cancer [87]. This evidence concerns the gene ERBB2 and breast cancer.