Relationship between oral mucositis and the oral bacterial count in patients with head and neck cancer undergoing carbon ion radiotherapy: A prospective study

Radiother Oncol. 2022 Feb:167:65-71. doi: 10.1016/j.radonc.2021.12.010. Epub 2021 Dec 10.


Background and purpose: Acute adverse events, such as oral mucositis, can affect treatment success in patients undergoing head and neck radiotherapy. In this study, we aimed to identify the relationship between oral mucositis and oral bacterial counts during carbon ion radiotherapy (C-ion RT) in patients with head and neck cancer.

Materials and methods: This prospective study included patients with head and neck tumors treated with C-ion RT between 2017 and 2019. C-ion RT consisted of treatment at 57.6, 64.0, or 70.4 Gy (relative biological effectiveness) in 16 fractions. Bacterial counts in the saliva and the back of the tongue were measured using a rapid oral bacteria quantification system. The relationship between the oral bacterial count and oral mucositis was subsequently analyzed.

Results: In total, 46 patients were included in the analysis. The bacterial count in the saliva gradually increased from the commencement of C-ion RT and peaked at 16 fractions. Bacterial counts at the back of the tongue were already high at the beginning of C-ion RT; however, they decreased with continued treatment, peaked at 16 fractions, and subsequently decreased again. Patients with bacterial counts exceeding the mean before C-ion RT (high-count group) did not experience more severe mucositis than those with counts below the mean (low-count group). However, patients in the high-count group tended to experience faster-onset mucositis and slower healing than those in the low-count group.

Conclusion: Bacterial counts may aid in the development of clinical strategies for C-ion RT-induced oral mucositis.

Keywords: Carbon ion radiotherapy; Head and neck tumor; Oral bacterial count; Oral mucositis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Load
  • Head and Neck Neoplasms* / etiology
  • Head and Neck Neoplasms* / radiotherapy
  • Heavy Ion Radiotherapy* / adverse effects
  • Humans
  • Mucositis* / etiology
  • Prospective Studies
  • Radiotherapy / adverse effects
  • Stomatitis* / etiology