ERBB2 and neoplasm: Among patients with extracranial metastases before the BM diagnosis, patients with an HER2-positive/hormone receptor-positive tumor biology had a significantly longer time period to development of extracranial metastases: the estimated 4-year extracranial metastases-free survival in HER2-positive/hormone receptor-negative patients was 16.2% (95% CI 12.2%-20.6%) versus 31.2% (95% CI 27.0%-35.5%) in HER2-positive/hormone receptor-positive patients.