Prognosis and Prediction in Breast Cancer: Is There a Need for Further Tests?

Paradigm shifts in diagnostic and therapeutic approaches in breast cancer substantially improved survival and quality of life. Since 1989 until 2015, the mortality rate decreased by 39% according to US breast cancer statistics (1). The first paradigm shift occurred once it was recognized that breast cancer is not a local but rather a systemic disease. Veronesi and coworkers demonstrated in a ground-breaking trial that breast-conserving surgery instead of mutilating radical mastectomy does not impact survival (2). The next paradigm shift emerged with the understanding that clinicopathological factors such as the axillary lymph node status, tumor size, incidence of metastases, and grade of cellular differentiation have prognostic value, which led to the introduction of adjuvant chemotherapy to reduce and prevent disease recurrence. Subsequently, the knowledge of the importance of the estrogen receptor (ER) not only identified patients with better overall survival but also led to the first targeted therapy approach, which blocked the estrogen receptor pathway (3). Further subtyping was enabled through the discovery of the human epidermal growth factor 2 (HER2) receptor by Slamon and coworkers (4). At the beginning of the new millennium, Perou et al. introduced intrinsic subtyping in the molecular pathology of breast cancer (5). Shortly thereafter, Sorlie and coworkers defined the molecular subtypes Luminal A, Luminal B, basal-like, …