Dosimetric verification of dental stent efficacy in head and neck radiation therapy using modern radiation therapy techniques: quality of life and treatment compliance implications

Abstract

Objective: During radiotherapy to the head and neck, metallic dental restorations produce secondary electrons that increase dose to nearby tissue causing painful ulcers that contribute to morbidity during treatment and lead to breaks in therapy. Various protective measures have been tested with simplified phantoms and beam arrangements. Our objective was to quantitatively assess electron scatter using an anatomical phantom and modern beam configurations. Methods: A tissue-equivalent phantom was created to simulate the oral cavity with gold crowns on opposing molars. Four-millimeter ethylene copolymer dosimetric dental stents were produced. The phantom was placed in a water bath to simulate soft tissue. Radiation was delivered in opposed lateral, nine-field intensity-modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT) configurations. A GafChromic EBT3 film was used to simulate the mucosal surfaces of the tongue and the buccal mucosa. The film readings were then converted to isodose plots using DoseLab. Results: With opposed beams, a 32 % reduction in maximum dose was measured in the occlusal plane with the use of stents. In the nine-field IMRT and VMAT plans, maximum dose to the adjacent film was reduced by approximately 40 % with the use of the dental stent. Conclusions: This approximately 40 % dose reduction implies that patients’ oral mucosae adjacent to dental fixtures could receive more than 100 Gy during a course of definitive radiotherapy to the head and neck without dental stents. In this era of increasing IMRT/VMAT utilization, our results emphasize the value of stent use to improve morbidity and reduce treatment breaks for patients undergoing head and neck radiotherapy.