Globally, T-DM1 has demonstrated a favorable safety and efficacy profile in both early- and late-stage HER2-positive patient populations, but in Asia, T-DM1 has been associated with a higher rate of thrombocytopenia than in non-Asian populations (Wuerstlein et al., 2022; Rainone et al., 2023b). This evidence concerns the gene ERBB2 and Thrombocytopenia.