ERBB2 and breast cancer: Primary outcomes were the cumulative incidence of treated brain metastases and time to brain metastasis (TTBM) as defined by the time from primary breast cancer diagnosis to brain metastases treatment.<h4>Results</h4>Among 92,973 patients, 7.9% had HER2+/HR+, 3.5% HER2+/HR-, 54.1% HR+/HER2-, 7.3% TNBC, and 27.2% unknown subtype.