How relevant is hormone receptor status in the context of outcome to HER2-positive breast cancer?

Clinical outcome of patients with breast cancer is based on patient and tumor-related factors. The relevant tumor-related factors include anatomical extent and biology. Of the prognostic and predictive biological markers available, hormone receptors (defined as estrogen and progesterone receptors) and HER2 receptors, have been independently validated. Pertinent questions to be addressed include their combined impact on prognosis, their relevance in terms of sites of metastases, and whether they change in primary versus recurrent tumors. Although these questions are being addressed in clinical trials, epidemiological results, such as those derived from the National Comprehensive Cancer Network dataset, add perspective to our understanding of these two most relevant biological prognostic/predictive markers.