Abstract
Simple SummaryPatients who receive carbon ion radiotherapy (C-ion RT) for tumors near the temporomandibular joint are likely to experience trismus, a condition characterized by reduced jaw opening. However, the relationship between the dose of carbon ion and the onset of trismus remains unclear. Therefore, we conducted a subgroup analysis of a prospective observational study to understand the relationship between the dose of carbon ion and the occurrence of trismus. Of 35 patients included in the study, six developed grade 2 trismus, and the median onset time was 12 months. The affected muscles included masticatory muscles and the coronoid process. Our findings suggest better treatment planning, such as dose optimization, to minimize the occurrence of muscle-related adverse effects associated with C-ion RT.Carbon ion radiotherapy (C-ion RT) provides a highly localized deposition of energy that can increase radiation doses to tumors while minimizing irradiation of adjacent normal tissues. For tumors located near the temporomandibular joint, C-ion RT-induced trismus may occur. However, the relationship between the carbon ion dose and the onset of trismus is unclear. In this prospective observational study, we assessed the trismus/carbon ion dose relationship using dose−volume histograms in 35 patients who received C-ion RT in their head and neck regions between 2010 and 2014. Trismus was evaluated in patients according to the Common Terminology Criteria for Adverse Events, version 4.0. All patients were treated with 57.6 or 64.0 Gy (relative biological effectiveness (RBE)) in 16 fractions, and the median follow-up time was 57 months. Grade 2 trismus was observed in six patients. The median onset time was 12 months. At maximum radiation doses, all masticatory muscles and coronoid processes, particularly the masseter muscle, were significantly different (p = 0.003). The contouring of the masseter muscle and coronoid process requires different treatment planning. The maximum radiation doses of the coronoid process can be proposed as a guideline for treatment planning, considering the ease of contouring in C-ion RT.
Highlights
Head and neck tumor patients undergoing radiotherapy suffer from acute adverse events, and late adverse events.Usually it is challenging to improve late adverse events that reduce the patient’s quality of life (QOL).Radiation-induced trismus impacts the patient’s QOL, making it difficult for them to open their mouths, to eat, to talk, and to maintain oral hygiene [1,2]
C-ion RT-induced trismus was evaluated using the Common Terminology Criteria for Adverse Events (CTCAE), version 4.0. [21], and grade 2 or higher was considered as trismus
Trismus onset showed no significant difference between the age, sex, primary site, histological type, T stage, and gross tumor volume (Table S1)
Summary
Head and neck tumor patients undergoing radiotherapy suffer from acute adverse events (mucositis and dermatitis), and late adverse events (dysgeusia, osteoradionecrosis, and trismus).Usually it is challenging to improve late adverse events that reduce the patient’s quality of life (QOL).Radiation-induced trismus impacts the patient’s QOL, making it difficult for them to open their mouths, to eat, to talk, and to maintain oral hygiene [1,2]. Previous studies showed trismus onset by X-ray correlated significantly with the radiation dose received in the masseter muscles [1,2,6,10,12], pterygoid muscles [1,13,14], and in the temporomandibular joint [2,15], focusing efforts on reducing the radiation dose received by the above structures to mitigate the X-ray-induced onset of trismus This is difficult when the tumor has invaded near the temporomandibular joint structures, increasing the concentration area of radiation-induced adverse events, since radiotherapy has become highly precise. The relationship between C-ion RT and trismus is unclear
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