Sequencing-based Counting of Plasma Epstein-Barr Virus DNA in Non-metastatic Nasopharyngeal Carcinoma

Inclusion Criteria: 1. Newly diagnosed, pathologically proven World Health Organization (WHO) type II/III untreated NPC; 2. Non-metastatic NPC (I-IVA, according to the 8th edition of the AJCC/UICC clinical staging system); 3. Age at diagnosis: over 18 years old; 4. Eastern Cooperative Oncology Group (ECOG) score: 0-1 5. Receiving recommended curative intention treatments：definitive radiotherapy w/wo three cycles of induction chemotherapy (IC) (gemcitabine-cisplatin \[GP\] or paclitaxel-cisplatin \[TP\] regimen); 6. Pre-treatment and post-IC1 cell-free Epstein-Barr virus (cfEBV) DNA \> 0 copy/mL; systemic cfEBV DNA monitoring during IC phase for risk stratification; 7. Normal hematic, liver, and kidney function: hemoglobin (HG) \> 90 g/L; neutrophil \> 1.5 × 109/L; platelet \> 100 × 109/L; total bilirubin (TBIL) ≤ 1.5 × upper limit of normal (ULN); alanine transaminase (ALT) and aspartate transaminase (AST) ≤ 2.5 × ULN; alkaline phosphatase (ALP) ≤ 2.5 × ULN; creatinine clearance (Ccr) ≥ 60 mL/min; 8. Female subjects capable of becoming pregnant agree to use reliable contraceptive measures from screening to 1 year after treatment; 9. Patients will be required to sign informed consent forms and be willing and able to comply with the requirements for visits, treatment, laboratory tests, and other research requirements stipulated in the research schedule. Exclusion Criteria: 1. Receiving surgery, target therapy, and/or immunotherapy during or before induction phase; 2. Other previous or concurrent malignant tumors, except adequately treated non-melanoma skin cancer, cervical carcinoma in situ, and thyroid papillary cancer; 3. Pregnant or lactating women (a pregnancy test should be considered for fertile women with an active sex life); 4. Previously treated with radical radiotherapy (RT), except non-melanoma skin cancers outside intended RT treatment volume; 5. Uncontrolled heart disease, e.g.: 1) Heart failure, New York Heart Association (NYHA) level ≥ 2; 2) unstable angina; 3) myocardial infarction in the past 1 year; 4) supraventricular or ventricular arrhythmia requiring treatment or intervention.