Based on these findings, T-DXd was included in the updated Guidelines of the National Comprehensive Cancer Network Clinical Practice (NCCN) as the preferred option for patients with HER2-low, who have received at least one prior line of chemotherapy for metastatic disease or if the tumor is HR+ and refractory to endocrine therapy in 2022(11). The gene discussed is ERBB2; the disease is neoplasm.