To explore the efficacy of Houyanqing Oral Liquid combined with conventional treatment in preventing and treating radiation-induced oral mucositis, so as to improve the quality of life of nasopharyngeal carcinoma patients received radiotherapy.

Nasopharyngeal carcinoma (NPC) is a highly prevalent malignant tumor in China. Radical radiotherapy serves as its core treatment modality, yet radiation-induced oral mucositis (RIOM) is the most common adverse reaction of radiotherapy, with an incidence rate as high as 85%-100%, among which 34% of patients develop grade 3-4 mucositis. RIOM can cause oral pain, ulcers, and dysphagia, which not only severely reduce patients' quality of life but also may lead to radiotherapy interruption, increased infection risk, and elevated treatment costs. Therefore, the prevention and treatment of RIOM are of great significance.

At present, conventional clinical prevention and treatment methods include oral hygiene maintenance, epithelial repair-promoting drugs (e.g., recombinant human epidermal growth factor spray, sodium aescinate for injection), and symptomatic supportive care, but there is no universally recognized standard regimen. Houyanqing Oral Liquid is a traditional Chinese medicine preparation composed of Achyranthes aspera L., Kalimeris indica (L.) Sch.-Bip., Plantago asiatica L., and Carpesium abrotanoides L. It possesses the effects of clearing heat and detoxifying, relieving sore throat and pain. Previous studies have confirmed that it exhibits significant efficacy in anti-inflammation, bacteriostasis, and mucosal injury repair, which can shorten the course of oral ulcers and reduce the recurrence rate.

This study intends to conduct a randomized controlled clinical trial to compare the efficacy of Houyanqing Oral Liquid combined with conventional treatment versus conventional treatment alone in preventing RIOM in NPC patients. It aims to verify the advantages of the combined regimen in reducing the incidence of ≥ grade II RIOM, delaying the onset time, alleviating the severity of injury, and improving patients' quality of life, so as to provide a more effective and safe prevention and treatment strategy for RIOM in clinical practice.

Inclusion Criteria:

1. Staged as Stage I-IV according to the 9th edition of the TNM Classification of Malignant Tumors formulated by the American Joint Committee on Cancer (AJCC) and the Union for International Cancer Control (UICC);
2. Age: 18 to 75 years old;
3. Karnofsky Performance Status (KPS) score ≥ 80 before treatment;
4. No oral diseases (such as oral mucositis or salivary gland damage) before radiotherapy;
5. Requiring radical radiotherapy;
6. The patient has signed the informed consent form and is willing and able to comply with the study's follow-up visits, treatment plan, laboratory tests, and other research procedures.

Exclusion Criteria:

1. Patients with confirmed tumor recurrence, distant tumor metastasis, or who have received other anti-tumor treatments;
2. Previous history of head and neck radiotherapy;
3. Known allergy to the drugs used in this study (Houyanqing Oral Liquid, any conventional treatment drugs);
4. Local use of Houyanqing Oral Liquid, Recombinant Human Epidermal Growth Factor (rhEGF) Topical Solution, Vitamin B12 Solution, or Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) mouthwash in the oral cavity within one month before enrollment;
5. Comorbidities requiring long-term treatment with immunosuppressive drugs, or systemic/local use of corticosteroids at immunosuppressive doses before enrollment;
6. HIV-positive patients;
7. Pregnant women or lactating women;
8. Patients with severe mental illnesses;
9. Patients with severe cardio-cerebrovascular diseases, endocrine disorders, infectious diseases, or other tumors.