The purpose of this study is to investigate the EBV reactivation rate in post-radiation and remission NPC patients, evaluate the safety and tolerance of EGCG and analyze the observational correlation between EBV reactivation and clinical outcome.

Patients with pathologically proven NPC, stage II-IVB and finishing curative RT ≧70 Gy within 6 months (± induction/concurrent/adjuvant chemotherapy) will be candidates for this study. Before entry, 8 CC venous blood will be obtained for EBV DNA and antibody screen tests after patient's consent. Those who have undetectable plasma EBV DNA (0 copy/ml) and fulfilled with all inclusion and exclusion criteria will be registered.

Routine re-staging work-ups after RT should show no active lesion in nasopharynx, neck and distant organs. Re-staging survey should include nasopharyngoscope, pEBV DNA assay, CBC, platelet count, renal and liver function tests, CXR, abdominal sonography or CT scan, whole body bone scan, MRI or CT scan of the head and neck region.

Within one week after finishing registration, EGCG or placebo should be started. A blood sample before taking EGCG/placebo will be collected for antibodies test and pEBV DNA assay.

Inclusion Criteria:

• Histologically proven NPC.
• 2010 AJCC stage II-IVB.
• Age ≧ 20 years old.
• Performance status of ECOG ≦ 2.
• Finished RT ≧66 Gy within 6 months (± induction/concurrent/adjuvant chemotherapy).
• Clinical complete remission by re-staging work-ups within 3 months before entry.
• Plasma EBV DNA = 0 copy/ml within 4 weeks before entry.
• Adequate liver, renal, and bone marrow function:Serum total bilirubin level ≦ 2.5 mg/dl. Serum creatinine ≦ 1.6 mg/dl. WBC ≧ 3,000/ul. Platelet count ≧ 100,000/ul.
• No intake of EGCG or similar dietary supplements.
• Signed informed consent.
• No further anti-cancer treatment.

Exclusion Criteria:

• Occurrence of locoregional recurrence or distant metastasis.
• Inadequate RT or finishing RT > 6 months.
• Not complete remission by re-staging work-ups within 3 months before entry.
• Plasma EBV DNA > 0 copy/ml within 4 weeks before entry.
• Intake of EGCG or similar dietary supplements during recent 3 months.
• Severe cardiopulmonary diseases (unstable angina and/or congestive heart failure or peripheral vascular disease requiring hospitalization within the last 12 months; chronic obstructive pulmonary disease exacerbation other respiratory illness requiring hospitalization) or clinically significant psychiatric disorders.