Effect of the Plasma EBV DNA Change During Chemoradiotherapy in Nasopharyngeal Carcinoma

Inclusion Criteria: 1. Histological proven NPC. 2. 2010 American Joint Committee on Cancer (AJCC) stage II-IVB. 3. Age ≧ 20 years old. 4. Performance status of Eastern Cooperative Oncology Group (ECOG) ≦ 2. 5. Adequate liver, renal, and bone marrow functions 5.1 Serum total bilirubin level ≦ 2.5 mg/dl. 5.2 Serum creatinine ≦ 1.6 mg/dl or calculated creatinine clearance rate (CCr) ≧ 60 cc/min. 5.3 White blood cell count (WBC) ≧ 3,000/micro-ml. 5.4 Platelet count ≧ 100,000/micro-ml. 6. Pre-treatment plasma EBV DNA \> 0 copies/mL 7. Signed informed consent. Exclusion Criteria: 1. Presence of distant metastasis. 2. Previous radiotherapy or chemotherapy. 3. History of a malignancy except those treated with curative intent for skin cancer (other than melanoma), in situ cervical cancer, ductal carcinoma in situ (DCIS) of the breast. 4. 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 or other respiratory illness requiring hospitalization) or clinically significant psychiatric disorders. 5. Female patients who are pregnant or lactating.