(29, 30) Thus, in patients with HR-negative/HER2-low breast cancers who have progressed after first-line pembrolizumab/chemotherapy, poly ADP-ribose polymerase inhibitors (PARPi) or systemic chemotherapy, both T-DXd and SG may be considered in the second-line setting as detailed within the NCCN guidelines. This evidence concerns the gene ERBB2 and breast cancer.