Prospective Cohort Study on Oral Microbiome Changes in Patients With Locally Advanced Oral Squamous Cell Carcinoma Following Neoadjuvant Chemoimmunotherapy

Inclusion Criteria: 1. Oral squamous cell carcinoma (OSCC) diagnosed as locally advanced (T3N0M0, T1-3N1M0, T4aN0-2M0, T1-4aN3M0, or T4bN0-3M0) according to AJCC staging criteria. 2. Their age ranged from 18 to 80 years;regardless of gender. 3. Absence of prior head and neck radiation therapy or chemotherapy. 4. Adequate blood function: white blood cell count (WBC) \>＝3.5×10\^9/L, platelet count (PLT) \>＝75×10\^9/L：Hemoglobin concentration (HGB) \>＝90g/L. 5. Adequate liver function： total bilirubin (TBIL) \<＝ the upper limit of normal, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) \<＝2.5 times the upper limit of normal. 6. Adequate renal function：estimated glomerular filtration rate (eGFR) greater than 45 mL/min per 1.73 m². 7. The heart, brain, lung and other vital organs function and general condition can tolerate NACI. 8. PS score \<＝2. 9. Signed informed consent form and voluntarily agreeing to participate in this study. Exclusion Criteria: 1. Pregnancy or lactation (for female participants). 2. Patients with a history of epilepsy or psychiatric disorders that were not well-controlled. 3. Patients with severe allergic diathesis or suspected or confirmed alcohol or drug addiction. 4. Patients who had taken antibiotics within 7 days before enrollment.