Hormone receptor expression is associated with a unique pattern of metastatic spread and increased survival among HER2-overexpressing breast cancer patients

OBJECTIVES:: HER2/neu (HER2) overexpression occurs in approximately 20% of breast cancers and is associated with aggressive disease. Although a significant number of HER2-positive tumors also express hormone receptors (HR), the effects HR expression has on clinical characteristics, including response to trastuzumab among HER2-positive breast cancer, has not been elucidated yet. METHODS:: A retrospective analysis of consecutive metastatic HER2-positive breast cancer patients was conducted in 2 medical centers. Associations between hormone receptors expression and clinical variables, and metastatic spread pattern and survival were studied. RESULTS:: The study population included 137 metastatic HER2-positive breast cancer patients, 56 of them were HR-positive and 81 were HR-negative. No significant differences between the 2 groups were found for demographic and clinical characteristics, including age, stage at diagnosis, tumor histology, and grade. Similar response rate to trastuzumab was observed in both study groups. Significantly, longer, median, disease-free, and overall survival was noted among the HR-positive patients. Patients in the HR-negative group had significantly more liver metastases, a trend for more brain metastases, and less bone metastases. There was a strong trend for more visceral metastases in the HR-negative group. CONCLUSIONS:: Our results suggest an important role for HR expression in modulating metastases predilection and disease progression in HER2-positive breast cancer.