This prospective, single-arm, Phase II clinical trial aims to evaluate the efficacy and safety of tislelizumab combined with chemotherapy as neoadjuvant therapy and postoperative adjuvant immunotherapy in patients with skull base-invading head and neck squamous cell carcinoma. The primary objectives are to address the following questions:

• What are the objective response rate and pathological response of tislelizumab combined with chemotherapy as neoadjuvant therapy in patients with skull base-invading head and neck squamous cell carcinoma?
• Can neoadjuvant therapy convert unresectable skull base-invading head and neck squamous cell carcinoma into a resectable condition?
• Can adjuvant immunotherapy after neoadjuvant therapy prolong patients' recurrence-free survival and overall survival? The researchers will administer neoadjuvant therapy (tislelizumab combined with chemotherapy) and adjuvant immunotherapy to patients with skull base-invading head and neck squamous cell carcinoma and assess the treatment's efficacy and safety.

Participants will:

• Receive neoadjuvant therapy every 3 weeks (tislelizumab 200mg on Day 1, nab-paclitaxel 260mg/m² on Day 1, cisplatin 75mg/m² on Days 1-3) for 3 cycles.
• Undergo surgical treatment within 3 weeks after completing neoadjuvant therapy.
• Receive (chemo)radiotherapy 4-6 weeks after surgery.
• Receive adjuvant immunotherapy (tislelizumab 200mg) every 3 weeks after (chemo)radiotherapy for 8 cycles.

Inclusion Criteria:

• Age 18 to 80 years, regardless of gender;
• Histologically confirmed squamous cell carcinoma (including gingiva, buccal mucosa, palate, oropharynx, maxillary sinus, or maxilla/mandible) with radiological evidence of skull base invasion;
• Measurable tumor lesions (meeting RECIST v1.1 criteria);
• Treatment-naïve primary T4b-stage patients (N any, per AJCC 8th Edition, 2017);
• ECOG PS score: 0-1;
• Medically fit for surgery and chemotherapy, with no surgical contraindications;
• Women of childbearing potential (18-49 years) must have a negative pregnancy test within 7 days before treatment. Sexually active men and women must agree to use effective contraception during the trial and for 3 months after treatment cessation;
• Willing to provide written informed consent and comply with scheduled follow-ups, treatments, lab tests, and other study requirements.

Exclusion Criteria:

• Previous anti-tumor treatments including chemotherapy, radiotherapy, or immunotherapy; Refusal to sign informed consent;
• Patients who refuse the study treatment protocol; patients unable to complete treatment as planned; or patients unable to comply with regular follow-up due to psychological, social, familial or geographical reasons;
• Patients with known allergies to any study medications;
• Patients with poor systemic conditions unfit for treatment: as determined by routine tests (complete blood count, blood biochemistry, ECG, chest X-ray, etc.). Poor systemic conditions include: hemoglobin <60g/L, WBC <3.0×10⁹/L, platelets <80×10⁹/L, or serum creatinine >133μmol/L - such patients may be recommended for conservative treatment;
• Patients with autoimmune diseases requiring long-term immunosuppressive or corticosteroid therapy;
• Pregnant or lactating women (pregnancy testing should be considered for sexually active women of childbearing potential);
• Patients with current or previous malignancies (except adequately treated non-melanoma skin cancer, cervical carcinoma in situ, or papillary thyroid carcinoma);
• Participation in other clinical trials within 30 days prior to enrollment;
• Other conditions that may compromise patient safety or compliance as assessed by investigators, including: severe comorbidities (including psychiatric disorders), significantly abnormal laboratory results, or other high-risk familial/social factors.

Study Protocol Statistical Analysis Plan (SAP) Informed Consent Form (ICF) Clinical Study Report (CSR) Analytic Code

Starting 6 months after publication

The researchers obtained study protocol, statistical analysis plan, informed consent form, clinical study report, analytic code via email communication.