Breast cancer with HER2/neu over-expression and hormone receptor positive status: A distinct biology and natural history

650 Background: HER2/neu over-expression (HER2+) occurs in approximately 25% of breast cancers and is often associated with a more aggressive disease. In this study we examined the effects of hormone receptor (HR) expression on clinical characteristics and natural history in HER2+ breast cancer. Methods: A retrospective review of 116 patients (pts) with HER2+, metastatic, breast cancer was performed. HER2+ was defined as positive if immunohistochemical staining was +3 or if FISH was positive. HR was defined as positive if either estrogen or progesterone receptors staining were positive, regardless of intensity. Results: Median age was 47 (range 26–69). The vast majority (90%) had invasive ductal carcinoma and 74% had grade III disease. Positive HR staining was found in 48 (41%) of the pts and negative HR staining in 68 (59%). No significant differences between the study groups were found in age, tumor histology, grade and number of involved metastatic sites at time of first recurrence. At first recurrence...