Predicting the Severity and Prognosis of Trismus after Intensity-Modulated Radiation Therapy for Oral Cancer Patients by Magnetic Resonance Imaging

Abstract

To develop magnetic resonance imaging (MRI) indicators to predict trismus outcome for post-operative oral cavity cancer patients who received adjuvant intensity-modulated radiation therapy (IMRT), 22 patients with oral cancer treated with IMRT were studied over a two-year period. Signal abnormality scores (SA scores) were computed from Likert-type ratings of the abnormalities of nine masticator structures and compared with the Mann-Whitney U-test and Kruskal–Wallis one-way ANOVA test between groups. Seventeen patients (77.3%) experienced different degrees of trismus during the two-year follow-up period. The SA score correlated with the trismus grade (r = 0.52, p<0.005). Patients having progressive trismus had higher mean doses of radiation to multiple structures, including the masticator and lateral pterygoid muscles, and the parotid gland (p<0.05). In addition, this group also had higher SA-masticator muscle dose product at 6 months and SA scores at 12 months (p<0.05). At the optimum cut-off points of 0.38 for the propensity score, the sensitivity was 100% and the specificity was 93% for predicting the prognosis of the trismus patients. The SA score, as determined using MRI, can reflect the radiation injury and correlate to trismus severity. Together with the radiation dose, it could serve as a useful biomarker to predict the outcome and guide the management of trismus following radiation therapy.

Trismus and reduced quality of life in patients with oral squamous cell carcinoma, who received post-operative radiotherapy alone or combined with chemotherapy

“…The absence of specific criteria for the definition of trismus and the non-homogeneous group of patients in the different studies are also some of the main reasons for the above wide variation of the prevalence of trismus in head and neck cancer patients [6,9,12,13].…”

“…Trismus to the head and neck area is related to the total RT dose [9]. Radiation dose equal to or higher than 60 Grays in patients, who had received IMRT, was related with an increased risk for development of trismus.…”

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

“…In another study of head and neck cancer patients treated with 3D-CRT or IMRT, the incidence of trismus was 28.3% (Steiner et al, 2015). Hsieh et al reported that 77.3% of the patients with oral cancer treated with IMRT experienced trismus over a course of 2 years (Hsieh et al, 2014). The result of the study was probably overestimated as there was a limited sample size of 22 patients; furthermore, the study failed to indicate the cut-off value for trismus and the approximate time interval between radiation and the measurement of MIO.…”

“…Reported incidences of trismus in oral and oropharyngeal cancer patients treated with IMRT can range from 4% to 77.3% (Hsieh et al, 2014; Rao et al, 2015; Ingle et al, 2010; Chao et al, 2004; Gomez et al, 2009). This wide range is likely due to different inclusion criteria; subjective or objective assessments of trismus, cut-off values for trismus, and follow-up periods.…”

A magnetic resonance imaging-based approach to quantify radiation-induced normal tissue injuries applied to trismus in head and neck cancer

“…Furthermore, five recent studies have pointed out that trismus is in particular explained by the dose to tumor-ipsilateral masticatory muscles [5, 8–11]. By means of magnetic resonance imaging (MRI) both Bhatia et al [12], and Hsieh et al [13] qualitatively identified abnormalities in multiple masticatory muscles that were associated with trismus. However, quantitative image measures may provide additional information, and identified metrics are likely to be more reproducible compared to qualitatively identified metrics [14, 15].…”