Recent evidence suggests that the prognosis of mCRCs and the activity of first-line regimens is also affected by the primary tumor site, with the right-side mCRCs characterized by a worst prognosis and RAS wild-type mCRCs arising in left colon being more sensitive to EGFR-based therapy compared to RAS wild-type mCRCs arising in right colon [17,18,19]. The gene discussed is EGFR; the disease is neoplasm.