['head and neck cancer']
['placebo', '2% rebamipide liquid', '4% rebamipide liquid']

        Inclusion Criteria:

          -  Head and neck cancer patients scheduled for definitive or postoperative
             chemoradiotherapy.

          -  Patients with a histopathological diagnosis of head and neck cancer and primary tumor
             in one of the following regions.

               1. Definitive therapy: nasopharynx, oropharynx, hypopharynx, or larynx

               2. Postoperative therapy: oral cavity, ropharynx, hypopharynx, or larynx

          -  Patients with no history of chemotherapy, radiotherapy, or chemoradiotherapy for head
             and neck cancer

          -  Patients with an Eastern Cooperative Oncology Group (ECOG) performance status score of
             0 or 1

          -  Patients who are able to hold fluid in the mouth

          -  Patients who are able to swallow the investigational medicinal product (IMP)

          -  Patients expected to survive for at least 3 months

          -  Patients who have given written informed consent in person

          -  Patients who can stay at or visit the hospital for scheduled examinations and
             observations

          -  Patients who are able to take contraceptive measures to avoid pregnancy of the patient
             or their partner from the time of informed consent until 4 weeks after completion of
             IMP administration

        Exclusion Criteria:

          -  Patients with primary malignant tumors other than head and neck cancer.

          -  Patients with symptomatic viral, bacterial, or fungal infection

          -  Patients with serious renal impairment

          -  Patients with distant metastasis

          -  Patients with severe complications (uncontrolled cardiac disease, diabetes,
             hypertension, etc)

          -  Patients with any of the following laboratory test results:

               1. Neutrophil count: <1500 L

               2. Platelet count: <75000 L

               3. Hemoglobin: <10.0 g/L

               4. Aspartate aminotransferase (AST): >3 times the upper limit of the reference value
                  at the trial site

               5. Alanine aminotransferase (ALT): >3 times the upper limit of the reference value
                  at the trial site

               6. Serum bilirubin: >1.5 times the upper limit of the reference value at the trial
                  site

               7. Serum albumin: <3.0 g/dL

               8. Serum creatinine: >1.5 the upper limit of the reference value at the trial site

               9. Creatinine clearance : <30 mL/min

          -  Patients complicated with autoimmune disease

          -  Patients requiring continuous systemic administration of glucocorticoid

          -  Female patients who are pregnant or lactating, who may possibly be pregnant, or who
             wish to become pregnant

          -  Patients who have participated in any other clinical trial within 4 weeks prior to
             initiation of chemoradiotherapy

          -  Patients who have a history of drug allergy to rebamipide, cisplatin, or other
             platinum compounds

          -  Patients who are otherwise judged by the investigator or sub-investigator to be
             inappropriate for inclusion in the trial
      