ERBB2 and metastatic colorectal cancer: However, few biomarkers can be used to stratify patients with regards to their response to a treatment, for example HER2 for predicting Trastuzumab efficacy for breast cancer [31], RAS for Cetuximab, and Panitumumab for metastatic colorectal cancer [9,32], BRAF for Vemurafenib efficacy for metastatic melanoma [33].