Investigating the Relationship Between Oral Microbiome Alterations and Tumor Markers in Locally Advanced Oral Squamous Cell Carcinoma (LA-OSCC) After Neoadjuvant Chemoimmunotherapy: Implications for Therapeutic Efficacy, Chemoresistance, and Prognostic Assessment

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.

Patients with locally advanced oral squamous cell carcinoma (OSCC) attending the Department of Stomatology, Zhujiang Hospital.