This study is a prospective, randomized, parallel-controlled clinical trial, with the primary objective to evaluate the efficacy and safety of nano-crystalline megestrol acetate combined with standard treatment compared to standard treatment alone for adjuvant therapy in patients with high-risk squamous cell carcinoma of the head and neck (excluding nasopharyngeal carcinoma) after surgery.

Inclusion Criteria:

• ≥18 years at the time of enrollment.
• Eastern Cooperative Oncology Group (ECOG) performance status score of 0-2.
• Life expectancy ≥6 months.
• Patients with histologically or cytologically confirmed squamous cell carcinoma of the head and neck (oral cavity, oropharynx, larynx, and hypopharynx).
• Patients who have undergone surgery for head and neck squamous cell carcinoma within 6 weeks and are assessed postoperatively as having high-risk factors requiring radiotherapy ± chemotherapy.

Exclusion Criteria:

• Suffering from tumors in areas other than the oral cavity, oropharynx, larynx, and hypopharynx, such as nasopharyngeal carcinoma or other unknown primary head and neck tumors.
• Having any condition that affects gastrointestinal absorption, such as dysphagia, malabsorption, or uncontrollable vomiting; currently undergoing tube feeding or parenteral nutrition.
• Suffering from anorexia due to neurosis, mental illness, or difficulty eating due to pain.
• Suffering from Acquired Immune Deficiency Syndrome (AIDS).