Trismus assessments

Three sources of information regarding trismus, all assessed at baseline and at 3/6/12 months post-RT, were considered for the present study. Two patient-reported outcome instruments were used: the GTQ ¹⁰, and the HNC-specific module of the European Organization for Research and Treatment of Cancer quality of life Questionnaire (EORTC QLQ-H&N35) ¹³. The GTQ includes 21 items on eating limitations, jaw-related problems, muscular tension, pain and impact on quality of life (QoL), generally with a one-week-recall period and with a 1–5 answering classification (1: not at all; 5: very severe) ¹⁰. The HNC-specific module of EORTC QLQ-H&N35 ¹³ includes 35 items classified from 1 to 4, of which the two items “Did you experience pain in your jaw” and “Did you have difficulties opening your mouth” were included here. The Likert scale answering categories of both patient-reported outcome instruments are translated into equally distributed scores between 0–100 (0/100 indicates the lowest/highest symptom severity). An overview of all considered GTQ and EORTC QLQ-HN35 items, and their answering categories are given in Table S1. MIO was measured with a ruler as the distance between the edges of the incisors of the mandible and the maxilla (mm accuracy), and with the subject in an upright position ¹¹.