Consideration of mouth opening when using positioning stents during radiotherapy for tongue cancer: a retrospective study

BACKGROUND: The aim was to clarify the range of mouth opening required to minimize the development of oral mucositis on the palate while using a positioning stent during radiotherapy in patients with tongue cancer. A positioning stent is used to reduce the severity of oral mucositis; however, requirements for fabricating the device have not been standardized. In particular, the range of mouth opening required while using a stent to prevent radiation-induced oral mucositis has not been determined. MATERIALS AND METHODS: We retrospectively analyzed medical records and computed tomography (CT) images of nine patients who had undergone radiotherapy for tongue cancer. Irradiation dose for the palate and range of mouth opening while using the positioning stent was calculated from CT images and the radiotherapy treatment planning program. RESULTS: The irradiation dose presented as medians and interquartile range (IQR) for the palate was 1.6 (IQR: 1.1–2.2) Gy with the use of the positioning stent and 37.2 (IQR: 17.5–44.1) Gy without the use of the positioning stent. The range of mouth opening was 19–37 [mean ± standard deviation (SD): 26 ± 5.6] mm, and it correlated with the attenuation amount of irradiation dose to the palate (r = 0.673, p = 0.0467). Regression equation was y = 0.21x + 19. CONCLUSIONS: Our study may be useful for deriving the relationship between the attenuation amount of irradiation of the palate with the positioning stent and the amount of mouth opening required for this attenuation.