In DESTINY‐Breast06 trial [38], which included HER2‐low and HER2‐ultralow metastatic breast cancer, grade ≥ 3 AEs occurred in approximately 41% of patients, most frequently neutropenia (20.7%), leukopenia (6.9%), and anemia (5.8%). This evidence concerns the gene ERBB2 and Decreased total leukocyte count.