Topical dexamethasone mouthwash reduces oral mucositis severity in head and neck cancer radiotherapy patients

PURPOSE: Radiation-induced oral mucositis is a frequent and debilitating complication of curative radiotherapy for head and neck cancer. This randomized, triple-blind, placebo-controlled, parallel-group trial evaluated whether a topical dexamethasone oral solution (0.5 mg/10 mL) used as a prophylactic mouthwash reduces the incidence and severity of radiation-induced oral mucositis. METHODS: Fifty-four patients with non-metastatic head and neck squamous cell carcinoma scheduled to receive ≥ 60 Gy radiotherapy were randomized 1:1 to dexamethasone mouthwash or placebo and instructed to gargle 10 mL four times daily during radiotherapy. The primary endpoint was the incidence and maximum severity of oral mucositis occurring during radiotherapy, defined as the highest grade recorded using the WHO Oral Toxicity Scale and NCI-CTCAE criteria v. 5. Secondary endpoints included patient-reported pain (VAS), dysphagia, treatment discontinuation, and mucositis status at 2 months. Fifty patients completed the study (25 per arm); four patients discontinued (reasons reported in Results). RESULTS: The dexamethasone group had significantly lower mucositis severity at all time points by WHO and CTCAE scales (all p < 0.01), a delayed peak severity (week 5 vs week 3), lower pain scores from weeks 4-7 (median VAS 0-3 versus 4-6; p < 0.01), and lower dysphagia at 2 months (32% vs 72%; p = 0.01). No grade 4 mucositis occurred in the dexamethasone arm; two grade 4 events occurred in placebo. There were no statistically significant differences in treatment discontinuation. Topical dexamethasone was well tolerated; no signal of treatment-related systemic steroid toxicity or increased oral infections was observed. CONCLUSION: In this phase II study, prophylactic topical dexamethasone mouthwash reduced the severity and delayed the onset of radiation-induced oral mucositis and improved patient-reported pain. These findings are promising but require confirmation in larger multicenter trials with longer follow-up and formal patient-reported outcomes (e.g., EORTC QLQ-H&N35, OMAS) and comparison with guideline-recommended strategies such as photobiomodulation. TRIAL REGISTRATION NUMBER: Iranian Registry of Clinical Trials; trial registration number: IRCT20240525061893N1; date of registration: 21 July 2024.