Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide, with a 5-year survival rate of less than 50%. Radiotherapy is an important measure to control tumor recurrence. Although radiotherapy has been widely used in patients with head and neck squamous cell carcinoma, the 2-year local recurrence rate of patients with locally advanced disease is still as high as 50%-60%, and the distant metastasis rate is as high as 20%-30%. This is associated with a lower radiosensitivity in HNSCC. Our previous study has confirmed that type I collagen secreted by cancer-associated fibroblasts (CAFs) can enhance the radioresistance of head and neck squamous cell carcinoma. We also confirmed that pirfenidone could reduce type I collagen expression in CAFs and enhance radiosensitivity in vitro and in vivo. Therefore, we plan to translate the basic research into clinical practice and conduct a prospective interventional phase II clinical trial to investigate the safety and efficacy of pirfenidone as a radiosensitizer in HNSCC.

Inclusion Criteria:

1. be at least 18 years old;
2. provide written informed consent;
3. head and neck squamous cell carcinoma confirmed by biopsy (2022 WHO criteria);
4. no previous head and neck radiotherapy;
5. The presence of measurable lesions: no surgical treatment or postoperative imaging evaluation indicated that the tumor was not completely resected;
6. ECOG PS: 0/1;
7. Laboratory confirmation of good organ function. It should be given within 10 days before the first dose of treatment; 8) expected survival time ≥3 months.

Exclusion Criteria:

1. no indications for or contraindications to radiotherapy after evaluation;
2. no oral medication;
3. pregnancy or lactation;
4. patients with known allergy to pirfenidone or other contraindications;
5. concurrent tumors (except cured basal cell or squamous cell skin cancer, and cervical cancer in situ);
6. patients had any serious coexisting medical conditions that could pose an unacceptable risk or negatively affect trial adherence. "For example, unstable heart disease requiring treatment, chronic hepatitis, kidney disease, poor condition, uncontrolled diabetes (fasting blood glucose > 1.5 × ULN), and mental illness."