More recent real-world data have found that at 24 months after diagnosis of metastatic disease, the cumulative incidence rate of CNS metastases was 29.2% [95% confidence interval (CI) 26.8% to 31.8%] and 49.0% (95% CI 45.7% to 52.5%) in patients with HER2-positive/hormone receptor-positive and HER2-positive/hormone receptor-negative BC, respectively.3 Here, ERBB2 is linked to breast cancer.