This randomized trial evaluates a multimodal surveillance strategy in nasopharyngeal carcinoma patients with high-risk N3 cervical lymph node involvement after radiotherapy. Patients are assigned to standard follow-up or an enhanced strategy using CEUS, imaging, and EBV DNA for risk assessment. The intervention group uses multimodal evaluation to identify high-risk patients who may undergo multidisciplinary review and selective neck dissection when indicated. The primary endpoint is failure-free survival (FFS). Secondary endpoints include OS, LRRFS, DMFS, and safety .

This is a multicenter, randomized controlled clinical trial evaluating a multimodal evaluation-guided surveillance and intervention strategy in patients with nasopharyngeal carcinoma (NPC) with high-risk N3-stage cervical lymph node involvement after radiotherapy. The study investigates whether combining contrast-enhanced ultrasound (CEUS), conventional imaging (CT/MRI), and Epstein-Barr virus (EBV) DNA monitoring can improve risk stratification, early detection of residual disease, and optimize subsequent treatment decision-making.

Eligible patients will be randomly assigned in a 1:1 ratio to receive either standard post-radiotherapy follow-up or a multimodal evaluation-guided surveillance and intervention strategy. In the control group, patients will receive standard follow-up care according to clinical guidelines. No CEUS or structured multimodal risk stratification will be applied in this group. In the intervention group, patients will undergo an enhanced follow-up strategy based on multimodal evaluation, which integrates CEUS, conventional imaging, and EBV DNA to stratify the risk of residual lymph node disease. Patients identified as high/ very high-risk may receive further multidisciplinary evaluation, and endoscopic selective neck dissection will be performed when indicated.

The primary endpoint is failure-free survival (FFS), defined as the time from randomization to the first occurrence of locoregional recurrence, distant metastasis, or death from any cause, whichever occurs first. Secondary endpoints include overall survival (OS), locoregional relapse-free survival (LRRFS), distant metastasis-free survival (DMFS), and treatment-related safety. Safety will be evaluated according to CTCAE version 5.0. A total of 80 patients will be enrolled across multiple centers in China.

Inclusion Criteria:

1. Aged 18 to 70 years.
2. Pathologically confirmed nasopharyngeal non-keratinizing carcinoma (differentiated or undifferentiated, i.e., WHO Type II or III).
3. Tumor staged as TanyN3M0 according to the 9th Edition of the American Joint Committee on Cancer/Union for International Cancer Control (AJCC/UICC) staging system.
4. ECOG performance status 0-1.
5. No previous neck dissection.
6. Adequate hematologic, hepatic, and renal function, defined as: white blood cell count ≥4.0 × 10^9/L, absolute neutrophil count ≥2.0 × 10^9/L, hemoglobin ≥90 g/L, platelet count ≥100 × 10^9/L, aspartate aminotransferase and alanine aminotransferase ≤2.5 × the upper limit of normal, and creatinine clearance ≥60 mL/min
7. Written informed consent provided prior to study enrollment

Exclusion Criteria:

1. Ongoing receipt of other antitumor treatment or concurrent participation in another interventional clinical trial.
2. Pregnancy or breastfeeding.
3. Severe concomitant disease that may, in the investigator's judgment, pose an unacceptable risk or compromise study compliance, including severe cardiac disease, severe pulmonary dysfunction, significant renal disease, or severe psychiatric illness.
4. History of another invasive malignancy within 5 years before enrollment, except for adequately treated basal cell carcinoma of the skin, cervical carcinoma in situ, or superficial bladder tumors (Ta, Tis, or T1).