ERBB2 and breast cancer: CDK4/6 inhibitors have yielded definitive results in HR-positive/HER2-negative advanced breast cancer (Kalinsky et al., 2023; Goetz et al., 2017; Lu et al., 2022; Piezzo et al., 2020), as confirmed by previous meta-analyses (Braal et al., 2021; Li et al., 2020a; Li et al., 2020b; Giuliano et al., 2019).