Induction Chemoimmunotherapy Followed by Deescalated Definitive Radiotherapy in Head and Neck Cancer

Prior treatment

• Occurrence of ≥ G4 toxicities during induction therapy and not suitable to receiving subsequent concurrent chemoradiotherapy or immunotherapy.
• Prior treatment with any PD-1/PD-L1 inhibitor.
• Major surgery for non-tumor reasons without full recovery of toxicity/complications before starting study treatment.

Other illness

• History of another active malignancy within 5 years, except cured basal cell carcinoma of skin, cervical carcinoma in situ, papillary thyroid carcinoma, or superficial bladder cancer.
• Active or history of autoimmune disease (e.g., interstitial pneumonia, uveitis, colitis, hepatitis, hypophysitis, vasculitis, myocarditis, nephritis, hyperthyroidism/hypothyroidism requiring hormone replacement). Exceptions: vitiligo, childhood asthma fully resolved without intervention; asthma requiring bronchodilator medical intervention is excluded.
• Active infection or unexplained fever \>38.5°C during screening (tumor fever allowed if judged by investigator).
• Congenital or acquired immunodeficiency (e.g., HIV infection), active hepatitis B (HBV-DNA ≥ 10\^4 copies/mL), or active hepatitis C (HCV-RNA above lower limit of detection).
• Allergy to cisplatin, macromolecular protein preparations, or any component of anti-PD-1 antibodies.

Lab values

• Uncontrolled cardiovascular disease: myocardial ischemia grade II or higher, myocardial infarction, poorly controlled arrhythmia (including QTc ≥ 470 ms), NYHA class III-IV heart failure, LVEF \< 50%, or myocardial infarction within 1 year.
• Any other condition that, in the investigator's judgment, would interfere with study participation or data collection (e.g., severe psychiatric illness, abnormal laboratory values, family or social factors).

Other

• Pregnancy or breastfeeding.

• Patients with head and neck squamous cell carcinoma (HNSCC) who have completed 2-3 cycles of induction chemotherapy plus PD-1 inhibitor and achieved deep response.
• Within 1 month of achieving deep response, subsequent concurrent chemoradiotherapy is determined by integrating MDT recommendation and patient's discretion.
  • 2\. Age 18 to 75 years (including 75). 3. Histopathologically confirmed HNSCC (excluding nasopharyngeal carcinoma). 4. Clinical stage T1-2N2-3M0 or T3-4N0-3M0 (AJCC 8th edition). 5. HPV or P16 negative. 6. ECOG performance status 0 or 1. 7. No contraindications to immunotherapy or radiotherapy. 8. Adequate organ function as defined by:
• WBC ≥ 3.0×10\^9/L, ANC ≥ 2.0×10\^9/L, PLT ≥ 100×10\^9/L, HGB ≥ 90 g/L (no transfusion or G-CSF within 14 days).
• TBIL ≤ 2.0×ULN, ALT/AST ≤ 2.5×ULN, BUN/CRE ≤ 1.5×ULN or creatinine clearance ≥ 60 mL/min.
• INR or PT ≤ 1.5×ULN (or within therapeutic range for anticoagulation).
• Myocardial enzymes within normal limits. 9. For women of childbearing potential: negative pregnancy test within 7 days prior to enrollment and use of effective contraception during treatment and for 2 months after last dose. Male participants must agree to use effective contraception for the same period.
  • 10\. Willing to sign informed consent and comply with follow-up.