Trismus in patients with oropharyngeal cancer: relationship with dose in structures of mastication apparatus.

Abstract

Our aim was to assess the correlation between the radiation therapy (RT) dose to the mastication apparatus and trismus of oropharyngeal cancer patients. Eighty-one patients treated with RT were analyzed. The masseter, pterygoid, and temporalis muscles and the coronoid and condyl were delineated on axial CT slices. The mean dose in these structures was correlated with outcome of quality of life questionnaires. Fifty-six (88%) patients responded; 16% of the patients scored grade 3/4 on the Head & Neck 35 "opening mouth" question. A significant correlation was observed between dose in masseter and pterygoid muscles and trismus (p= .02). Patients treated with brachytherapy received a lower dose in masticatory muscles. A steep dose-effect relationship between mean dose in masseter muscle and pterygoid muscles and the probability of having trismus complaints was observed; with every additional 10 Gy to the pterygoid muscle, an increase of the probability of trismus of 24% was observed.