Quality assurance of dysphagia-optimised intensity modulated radiotherapy treatment planning for head and neck cancer

Abstract

This study aimed to assess the impact of the margin applied to the clinical target volume, to create the planning target volume, on plan quality of a novel dysphagia-optimised intensity modulated radiotherapy technique developed within a head and neck cancer multicentre randomised controlled trial. Protocol compliant plans were used for a single benchmark planning case. Larger margins were associated with higher doses to adjacent organs at risk, particularly the inferior pharyngeal constrictor muscle, but coincided with some improved low dose target coverage. A 3 mm margin is recommended for this technique if local practices allow.

Keywords: CERR, Computational Environment for Radiotherapy Research; DARS, dysphagia/aspiration related structures; DICOM, Digital Imaging and Communications in Medicine; DO-IMRT, dysphagia optimised intensity modulated radiotherapy; Dysphagia; Head and neck cancer; ICR-CTSU, Clinical Trials and Statistics Unit and the Institute of Cancer Research; IPCM, inferior pharyngeal constrictor muscle; Intensity modulated radiotherapy (IMRT); NIHR, National Institute for Health Research; PAF, plan assessment form; Quality assurance; RTQA, radiotherapy quality assurance; RTTQA, UK’s National Radiotherapy Trials Quality Assurance Group; Randomised controlled trial; S-IMRT, standard intensity modulated radiotherapy; SMPCM, superior and middle pharyngeal constrictor muscles; TMG, Trial Management Group; Volumetric arc therapy (VMAT).