De-Escalation Postoperative Radiotherapy for Oral Squamous Cell Carcinoma With pCR/MPR.

Inclusion criteria

• Untreated, histologically confirmed oral cavity carcinoma, staging T2-4N0M0 or T1-4N1-3M0, II-IVB, according to the eighth edition of the AJCC staging system.
• Pathological evaluation of surgical specimens was pCR (pathologic complete response, no viable tumor cells) or MPR (Major pathologic response, residual viable tumor cells≤10%).
• Negative surgical margin.
• No extranodal extension.
• Aged ≥ 18 years and ≤ 80 years.
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1.
• Life expectancy of more than 6 months.
• Women of childbearing age should agree to the use of contraception (e.g., intrauterine devices, birth control pills, or condoms) during treatment and for 3 months thereafter.
• The regimen of neoadjuvant therapy can be determined by the clinician.
• Subjects voluntarily join the study and sign an informed consent form, with good compliance.

Exclusion criteria

• Pregnant or lactating women.
• A history of other malignant tumors within the previous 5 years or at the time of enrollment, except for cured skin basal cell carcinoma and cervical in situ cancer, as well as thyroid papilloma.
• Neoadjuvant therapy or radical surgery was not completed.
• Recurrence or distant metastasis occurred before postoperative radiotherapy.
• There are contraindications for radiotherapy, chemotherapy, immunotherapy and targeted therapy.
• Uncontrolled cardiac clinical symptoms or diseases.
• Serious infections.
• A history of immunodeficiency, including HIV-positive status or other acquired congenital immunodeficiency diseases, or a history of organ transplantation and bone marrow transplantation.
• Patients with active tuberculosis infection found by history or CT examination, or patients with active tuberculosis infection history within 1 year prior to enrollment, or patients with active tuberculosis infection history before 1 year without formal treatment.
• Active hepatitis B (HBV DNA ≥ 2,000 IU/mL or 10,000 copies/mL) or hepatitis C (positive HCV antibody test and HCV RNA above the lower limit of detection).
• Known history of psychotropic drug abuse, alcoholism and drug use.
• Not suitable for inclusion, as judged by the investigator.