This study aims to evaluate the efficacy and safety of concurrent chemoradiotherapy based of cisplatin with sintilimab as first-line therapy for patients with advanced oral cavity squamous cell carcinoma.

Inclusion Criteria:

1. Volunteer to participate in clinical research; fully understand and know the research and sign informed consent.
2. Age ≥18 years, and ≤75years , either sex.
3. Eastern Collaborative Oncology Group Performance status (ECOG PS) 0 ,1 or 2.
4. Eastern Collaborative Oncology Group Performance status (ECOG PS) 0 ,1 or 2.
5. Patients with oral squamous cell carcinoma (including gingival cancer, tongue cancer, lip cancer, buccal cancer, oral cancer, etc) diagnosed by histopathology (according to the 8th edition of AJCC).
6. Initial diagnosis patients unable to perform surgery.
7. Have at least one measurable lesion as defined by RECIST 1.1.
8. Normal hepatic function: total bilirubin≤1.5×normal upper limit (ULN); Alanine aminotransferase and Aspartate aminotransferase levels ≤2.5×ULN or ≤5×ULN if liver metastasis is present.
9. Normal renal function ：Creatinine ≤1.5×ULN or calculated creatinine clearance ≥45 mL/min (using Cockcroft/Gault formula to calculate ).
10. Normal hematological function：absolute neutrophil count ≥1.5×109/L, platelet count ≥70×109/L, hemoglobin≥80g/L [no blood transfusion or erythropoietin (EPO) within 7 days] Dependency].
11. Has a life expectancy of at ≥3 months.

Exclusion Criteria:

1. ECOG PS >2.

2. Patients who received radiotherapy, chemotherapy, monoclonal antibody and oral EGFR-TKI therapy within three months.

3. Patients who are receiving any other investigational agents within 30 days prior to entering the study.

4. The tumor has metastasized to the brain and / or pia mater.

5. History of other malignancies (except for cured cervical carcinoma in situ or skin basal cell carcinoma and other malignancies that have been cured for more than 5 years).

6. Accompanied by other serious diseases, including but not limited to:

   Uncontrollable congestive heart failure (NYHA grade Ⅲ or Ⅳ), unstable angina, poorly controlled arrhythmia, uncontrolled moderate or above hypertension (SBP > 160mmhg or DBP > 100mmhg) ; Severe active infection; Uncontrollable diabetes (refers to the high fluctuation of blood glucose, the impact on patients' life and the frequent occurrence of hypotension despite the standard insulin treatment and frequent blood glucose monitoring) ; Mental illness affecting informed consent and / or program compliance.

7. Those who are allergic to the drug or its components used in the program.

8. Pregnancy (confirmed by hCG test in blood or urine) or lactating women, or childbearing age subjects are unwilling or unable to take effective contraceptive measures (applicable to both male and female subjects) until at least 6 months after the last trial treatment.

9. Those who are not considered suitable for the study by the researchers.

10. Unwilling to participate in this study or unable to sign informed consent.