Objective assessment of trismus in oral and oropharyngeal cancer patients treated with intensity-modulated radiation therapy (IMRT)

Abstract

Purpose The aim of this study was to estimate the incidence of trismus in oral and oropharyngeal cancer patients (OOPC) treated with intensity-modulated radiation therapy (IMRT) and to identify the role of risk factors in patients who developed trismus. Materials and Methods A retrospective cohort study of OOPC treated with IMRT in our institution from 2009 through 2014 was performed. Patients eligible for this study had pre-RT and post-RT maximal inter-incisal opening (MIO) measurements at 6 – 48 months post-RT, treated with high-dose radiation (≥60 Gy) and pre-RT MIO ≥ 36 mm. A descriptive analysis to identify the incidence of trismus, with trismus stated as MIO ≤ 35 mm at or after 6 months post-RT measurement was performed. The role of risk factors such as age, gender, tumor site, tumor size (T), tumor stage, pre-RT MIO measurements and radiation dose to the tumor were assessed using Fisher exact test and the radiation doses to the ipsilateral muscles of mastication in patients who developed trismus were assessed by matching with control (non-trismus) patients using Wilcoxon Signed Rank test. Results The study consisted of 54 patients with a median age of 55 years and 81% were males. The median follow-up time was 10 months. The incidence of trismus was 14.8%. Patients with pre-RT MIO measurements ≤40 mm were at risk of developing trismus (P<0.001). In trismus patients, the average mean radiation dose to the masseter and medial pterygoid muscles was numerically higher but not significantly different (P=0.08; P=0.22, respectively) to matched control patients. Age, gender, radiation dose to the tumor, tumor site, size (T) and stage were also found to be not significant. Conclusion Pre-RT MIO measurement was a significant risk factor for the development of trismus. However, this is a non-modifiable factor. Limiting radiation dose to the muscles of mastication could prevent this complication.

Comparison of mean radiation dose and dosimetric distribution to tooth-bearing regions of the mandible associated with proton beam radiation therapy and intensity-modulated radiation therapy for ipsilateral head and neck tumor

“…Trismus is another well-known complication of radiotherapy 32, 33 . The condition is defined as difficulty with mouth opening secondary to spasm of the muscles of mastication; a maximal interincisal opening measurement of ≤ 35 mm is considered trismus 34 .…”

Trismus in patients with head and neck cancer and 5-year overall survival

“…All patients in our study were treated with 3DCRT, which has now been replaced in many centers with modern IMRT. Several reports demonstrate that IMRT is probably less likely to cause trismus [6,18,19]. Further studies on IMRT are required with regard to trismus and our study provides a basis for comparison with 3DCRT.…”

Radiotherapy‐induced oral morbidities in head and neck cancer patients

“…A reported prevalence of trismus was 5‐14% when IMRT was used in comparison to 25.4% when conventional radiation therapy protocol was followed for HNC patients. Although there are no clear guidelines for the prevention and/or treatment of radiation‐induced trismus, the pre‐RT maximal interincisal opening is considered a risk factor in the development of trismus 125,126 . It has also been advised not to burden the patients who undertake high doses of radiation with an intense prophylactic training program during RT and up to 12 months after the completion of RT 96 .…”