Trismus following radiotherapy to the head and neck is likely to have distinct genotype dependent cause

Objectives: Trismus frequently occurs as a consequence of radiotherapy or chemo-radiotherapy to the head and neck, with a loss of function that can reduce the overall quality of life. Radiation can trigger an intense fibrosis within the masticatory muscles and transforming growth factor beta 1 (TGF beta 1) is involved in this process. As in other tissues the degree of fibrosis may be related to a single nucleotide polymorphism; C-T at position -509 in the TGF beta 1 gene. Materials and methods: Trismus was measured in 62 patients before and after radiotherapy or chemoradiotherapy, blood was taken for DNA extraction, and genotype analysis of the TGF beta 1 gene. Trismus was analysed against, patient age, sex, tumour site and stage, radiotherapy, and chemotherapy. Results and conclusions: After radiotherapy or chemo-radiotherapy the reduction in mouth opening was shown to be significantly related to the presence of the T allele (p < 0.001), with patients homozygous the most likely to be severely affected. No other patient, tumour or treatment factors were significant. Hence the TGF beta 1 genotype is likely to be an important predictor of the degree of post radiotherapy or chemo-radiotherapy trismus. (c) 2013 Published by Elsevier Ltd.