2862 - Potential Contribution of Specific Oral Bacteria to Radiation-Induced Mucositis in Head and Neck Cancer

Purpose/Objective(s): To investigate the association between changes in oral bacterial flora and the development of oral mucositis resulting from radiotherapy for head and neck cancer.

Materials/Methods: This prospective observational study enrolled patients receiving radiotherapy for head and neck cancer. Oral samples were collected at three time points: before, during, and after radiotherapy. The composition of oral bacteria was analyzed using 16S rRNA gene sequencing. Oral mucositis was assessed based on the Radiation Therapy Oncology Group (RTOG) criteria. The relationship between changes in oral bacterial flora and the severity of oral mucositis was analyzed.

Results: A total of 43 patients were included in the study. Before treatment, 15 genera were identified as core bacteria (defined as those with a relative abundance of =1%). Throughout the treatment period, more than 50% of the oral microbiota was composed of the four predominant genera: Streptococcus, Prevotella, Veillonella, and Rothia. A statistically significant decrease (p<0.05) in the relative abundance of Rothia, Haemophilus, Neisseria, and Lautropia was observed after treatment. The study then compared changes in core bacterial abundance before and after treatment between two groups: patients with oral mucositis of Grade 3 or higher and those with Grade 2 or lower. The results showed that three genera (Fusobacterium, Capnocytophaga, and Parvimonas) significantly increased in the Grade 3 or higher group (p < 0.05). Furthermore, the extent of these changes positively correlated with the severity of oral mucositis (p < 0.05).

Conclusion: Oral mucositis associated with radiotherapy for head and neck cancer was significantly associated with an increase in the relative abundance of specific oral bacteria. In particular, an increase in Fusobacterium, Leptotrichia, Capnocytophaga, and Parvimonas was correlated with mucositis severity.