The head and neck squamous cell carcinoma is the sixth most common malignant tumor worldwide. For patients with locally advanced head and neck cancer, neoadjuvant therapy is recommended before surgery, including neoadjuvant chemotherapy and immunotherapy. There is a significant variation in patients' responses to neoadjuvant therapy, with approximately 37%-52% of patients achieving a complete pathological response after neoadjuvant therapy. Current research mainly focuses on the efficacy evaluation of the primary tumor, while there is less research on the treatment efficacy evaluation of cervical lymph nodes. In clinical practice, accurate assessment of the status of cervical lymph nodes after neoadjuvant chemoimmunotherapy in patients with squamous cell carcinoma of the head and neck can directly affect the choice of treatment plan by clinicians, reducing unnecessary neck dissection. In recent years, contrast-enhanced ultrasound has been widely used in the diagnosis of thyroid cancer and other head and neck tumors, as well as in the assessment of the benign and malignant nature of cervical lymph nodes. This study aims to explore the value of contrast-enhanced ultrasound in the assessment of cervical lymph nodes after neoadjuvant chemoimmunotherapy in squamous cell carcinoma of the head and neck, in order to guide clinicians in formulating personalized treatment plans.

Inclusion Criteria:

• (1) Histopathologically confirmed head and neck squamous cell carcinoma; (2) Received neoadjuvant chemoimmunotherapy; (3) Diagnosed with cN+ by CT/MRI before treatment; (4) Underwent radical surgical treatment plus cervical lymph node dissection at this center.

Exclusion Criteria:

• (1) Did not receive a full course of neoadjuvant therapy; (2) History of treatment for head and neck; (3) Clinical evidence of distant metastasis found during preoperative examination.

Patients with HNSCC, who treated in Sun Yat-Sen Memorial Hospital of Sun Yat-Sen University