Late dysphagia after changes in high-dose clinical tumour volume margin for head and neck cancer patients

Background and purpose: One of the factors influencing disease control and toxicity risk after radiotherapy is selection of treatment volume margin. This study evaluates whether different gross tumour volume (GTV) to high-dose clinical target volume (CTV1) margins impact dysphagia in a cohort of head and neck squamous cell carcinoma (SCC) patients. Patient/material and methods: Data of patients receiving primary IMRT-based radiotherapy for SCC for the oropharynx, hypopharynx, and larynx at three treatment centres between 2010 and 2015 were retrospectively collected. Treatment planning followed two DAHANCA guideline periods: pre-2013 (varying GTV-CTV1 margins), and post-2013 (isotropic 5 mm margin). Treatment plans were collected for 1,913 patients. GTV–CTV1 margins were calculated as median surface distance from GTV to CTV1. Dysphagia was graded using modified DAHANCA ordinal scale. For each patient, the highest score of dysphagia during 5-year follow-up period was chosen for analysis. Results: Dysphagia data were available for 1,706 patients (89%). The median GTV–CTV1 margin was 9.0 mm in 2010–2012 and 4.7 mm in 2013–2015. The severity of dysphagia was more pronounced in patients treated during 2010–2012 (p = 0.003). Predictors of grade ≥ 2 dysphagia included larger GTV (odds ratio [OR]: 1.7; p < 0.001), larger GTV–CTV1 margin (odds ratio [OR] of 1.3 per cm; p = 0.04), and tumour localisation other than oropharyngeal p16+carcinomas (p = 0.002). Male sex, non/previous smoking status, and application of chemotherapy were associated with less severe dysphagia. Interpretation: Tumour volume and GTV–CTV1 margin are dominant geometric parameters influencing dysphagia risk following curative radiotherapy