Utility of intraoral stents in external beam radiotherapy for head and neck cancer.

Abstract

This study aimed to assess the utility and stability of intraoral stent during intensity-modulated radiation therapy (IMRT). The benefits of intraoral stents in radiotherapy are unclear. We analyzed 386 setup errors in 12 patients who received IMRT for head and neck cancers without intraoral stents (intraoral stent [-]) and 183 setup errors in 6 patients who received IMRT with intraoral stents (intraoral stent [+]). All patients were matched according to the immobilization method (masks and boards). Setup errors were measured as the distance from the initial setup based on the marking on the skin and mask to the corrected position based on bone matching on cone beam computed tomography. The mean interfractional setup errors in the right-left, craniocaudal, anterior-posterior (AP), and three-dimensional (3D) directions were -0.33, 0.08, -0.25, and 2.75mm in the intraoral stent (-) group and -0.37, 0.24, -0.63, and 2.42mm in the intraoral stent (+) group, respectively (P=0.50, 0.65, 0.01, and 0.02, respectively). The systematic errors for the same directions were 0.89, 1.46, 1.15, and 0.88mm in the intraoral stent (-) group and 0.62, 1.69, 0.68, and 0.56mm in the intraoral stents (+) group, respectively. The random errors were 1.43, 1.43, 1.44, and 1.22mm in the intraoral stent (-) group and 1.06, 1.11, 1.05, and 0.92mm in the intraoral stents (+) group, respectively. Setup errors can be significantly reduced in the AP and 3D-directions by using intraoral stents.