Spirulina Derivative for Radiation Esophagitis

Inclusion Criteria: 1. Patients with histopathologically confirmed malignant esophageal tumor and no distant metastasis; 2. Age ≥ 18 years; 3. ECOG (Eastern Cooperative Oncology Group) performance status score ≤ 2; 4. Scheduled to undergo definitive radiotherapy, neoadjuvant radiotherapy, or adjuvant radiotherapy for esophageal cancer; 5. Adequate hepatic, renal, and bone marrow function; 6. Signed informed consent form. Exclusion Criteria: 1. History of prior thoracic radiotherapy. 2. Known allergy to spirulina or its derivatives, any component of the thermosensitive gel, or having a history of severe allergic predisposition. 3. Presence of esophageal or oral diseases assessed by the investigator before radiotherapy initiation that may affect the analysis of this study's results (e.g., reflux esophagitis, Barrett's esophagus, severe oral infection, recurrent aphthous ulcers, oral lichen planus, etc.). 4. Use of systemic antibacterial or antifungal medications within one week prior to the start of radiotherapy. 5. Planned concurrent use of medications that may exacerbate radiation-induced mucosal injury after radiotherapy initiation (e.g., anti-EGFR monoclonal antibodies, immune checkpoint inhibitors, etc.). 6. Presence of severe underlying diseases of the cardiovascular, pulmonary, hepatic, renal, hematopoietic, or nervous systems (specific criteria for organ dysfunction are detailed in item 7 below), or conditions such as acute infection, uncontrolled autoimmune diseases, poorly controlled diabetes mellitus, etc., which, in the investigator's judgment, may increase study risks or interfere with result analysis. 7. Presence of significant organ dysfunction meeting any of the following criteria: * Hemoglobin \< 80 g/L; * Neutrophil count \< 1.0 × 10⁹/L; * Platelet count \< 80 × 10⁹/L; * Serum total bilirubin ≥ 2 times the upper limit of normal (ULN); * Aspartate aminotransferase (AST) or alanine aminotransferase (ALT) ≥ 2.5 times ULN; * Serum creatinine \> 1.5 times ULN. 8. Pregnant or lactating women. 9. History of severe mental illness, alcohol abuse, or drug abuse. 10. Participation in other clinical trials within the past 3 months. 11. Any other condition deemed by the investigator as potentially rendering the subject unsuitable for participation in this study (e.g., extremely poor oral hygiene, poor compliance, etc.).