Interestingly, the incidence of oral mucositis was higher (all grades: about 30–40%, grade 3 or higher: approximately 10%) when the anti-EGFR antibody was used in combination with 5-fluorouracil (5-FU) [21–25], which is a well-known mucotoxic drug [26]. The gene discussed is EGFR; the disease is mucositis.