Based on this evidence, and investigating these hypotheses, a pilot study was designed to determine and compare the GM of patients with metastatic CRC undergoing first-line chemotherapy with or without a biological agent (antiepidermal growth factor receptor [EGFR] or antivascular endothelial growth factor [VEGF]), and receiving, based on random allocation, either a free choice Standard Western Diet (SWD), or a Modified Mediterranean Diet (MMD). This evidence concerns the gene EGFR and colorectal carcinoma.