This retrospective observational study will evaluate clinical data already available from adult cancer patients who developed cancer therapy-related oral mucositis during radiotherapy and/or chemotherapy and who were managed in routine clinical practice with combined chairside and domiciliary ozone therapy.

The study will not assign participants to any treatment and will not involve any new intervention, visit, examination, or change in patient care. Data will be extracted from existing medical records and clinical documentation.

The main purpose of the study is to describe the clinical course of oral mucositis and to evaluate the time needed to reach oral mucositis grade 1 or lower according to the World Health Organization Oral Toxicity Scale. The study will also assess changes in oral pain intensity, measured using a 0 to 10 Visual Analogue Scale, from baseline to follow-up visits up to 15 days.

Exploratory analyses will compare clinical trends between patients with head and neck cancers and patients with cancers in other anatomical sites. The results will be interpreted as descriptive and exploratory because the study is retrospective, single-arm, and has no control group.

Oral mucositis is a clinically relevant complication of anticancer treatments, especially radiotherapy and chemotherapy. It can cause erythema, ulcerations, oral pain, dysphagia, impaired oral intake, and reduced quality of life. In routine clinical practice, selected patients with cancer therapy-related oral mucositis were managed with a combined ozone-based protocol including professional chairside ozone application and domiciliary ozonized oral care products.

This study is designed as a retrospective observational analysis of data already available from medical records and clinical documentation. No prospective enrollment, treatment allocation, randomization, study-specific intervention, biological sampling, imaging, or additional clinical visit will be performed.

The study will include adult oncological patients with documented cancer therapy-related oral mucositis grade 1 or higher according to the World Health Organization Oral Toxicity Scale. Available data will include demographic and clinical information, oncological disease site, oral mucositis severity, and oral pain intensity measured using a 0 to 10 Visual Analogue Scale.

The retrospective observation period includes clinical data collected during routine care between November 2023 and September 2025. Outcome data will be analyzed from baseline to available follow-up visits up to 15 days. Additional exploratory analyses will describe clinical trends according to cancer site, comparing patients with head and neck cancers with patients with malignancies in other anatomical sites.

The findings will be interpreted as descriptive and exploratory, because the study is retrospective, single-arm, and does not include a control group.

Inclusion Criteria:

• Age 18 years or older
• Oncological patients undergoing radiotherapy and/or chemotherapy
• Clinical diagnosis of cancer therapy-related oral mucositis grade 1 or higher according to the World Health Organization Oral Toxicity Scale
• Availability of clinical documentation including World Health Organization Oral Toxicity Scale assessments and Visual Analogue Scale pain scores at baseline and at one or more follow-up timepoints
• Availability of relevant demographic and clinical information required for the retrospective analysis

Exclusion Criteria:

• Age younger than 18 years
• Absence of a documented diagnosis of cancer therapy-related oral mucositis
• Incomplete or unavailable clinical documentation for the primary and/or main secondary outcome
• Missing baseline World Health Organization Oral Toxicity Scale assessment
• Missing baseline Visual Analogue Scale pain assessment
• Any condition making the available data unsuitable for retrospective analysis

Adult oncological patients with cancer therapy-related oral mucositis whose clinical data are already available in medical records and/or clinical documentation. Patients were previously managed in routine clinical practice for oral mucositis occurring during radiotherapy and/or chemotherapy. The study population includes patients with documented oral mucositis grade 1 or higher according to the World Health Organization Oral Toxicity Scale and available baseline and follow-up assessments of oral mucositis severity and oral pain intensity. No prospective enrollment, treatment assignment, or study-specific intervention will be performed.

Data will be available upon motivated request to the corresponding authors.