Bench to bedside: research influencing clinical practice in breast cancer

Based on recent evidence derived from clinical trials and translational research, breast cancer pathology has witnessed a rapid increase in the utilization of predictive markers, companion diagnostics and molecular testing for tailored management of patients with breast cancer. New diagnostic entities with specific molecular phenotypes have also been included in the classification of breast cancer. Genomic assays including Oncotype DX®21-gene Recurrence Score (RS), Prosigna and EndoPredict are currently used in routine practice to guide adjuvant/neoadjuvant therapy. The analysis of established biomarkers such as ER and PR immunohistochemistry has been updated to recognize new categories with different clinical behaviour and significance, such as the ER low expressors and HER2 low carcinomas. PD-L1 testing and PIK3CA mutation have been introduced for advanced TNBC and recurrent ER positive breast cancer respectively. This review provides an update on the rapidly evolving field of predictive & prognostic markers, companion diagnostics, molecular and genomic testing of breast cancer.