,5,12,20 Use of T-DM1 as second-line treatment in patients with HER2-positive BC is further supported by results from real-world studies (Supplementary Table S5, available at https://doi.org/10.1016/j.esmoop.2022.100561).7, 8, 9, 10 Although the retrospective nature of some real-world studies may limit availability of safety data, findings from these studies have generally been comparable to those reported in clinical trials. Here, ERBB2 is linked to breast cancer.