Dose to medium in head and neck radiotherapy: Clinical implications for target volume metrics

作者：Nicholas Hardcastle, Atousa Montaseri, Jenny Lydon, Tomas Kron, Glen Osbourne, Georgina Casswell, David D. Taylor, Lisa Hall, Lachlan J. McDowell · 发表于：Physics and Imaging in Radiation Oncology · 年份：2019 · DOI：10.1016/j.phro.2019.08.005 · 被引用次数：13 · 研究领域：Head and Neck Cancer Studies、Advanced Radiotherapy Techniques、Radiation Dose and Imaging

Background and purpose In radiotherapy dose calculation, advanced type-B dose calculation algorithms can calculate dose to medium ( D m ), as opposed to Type-B algorithms which compute dose to varying densities of water ( D w ). We investigate the impact of D m on calculated dose and target coverage metrics in head and neck cancer patients. Methods and materials We reviewed 27 successfully treated (disease free at two-years post-(chemo)radiotherapy) human papillomavirus-associated (HPV) oropharyngeal cancer (ONC) patients treated with IMRT. Doses were calculated with Type-B and Linear Boltzman Transport Equation (LBTE) algorithms in a commercial treatment planning system, with the treated multi-leaf collimator patterns and monitor units. Coverage for primary Gross Tumour Volume (GTVp), high dose Planning Target Volume (PTV) (PTV_High), mandible within PTV_High (Mand ∩ PTV) and PTV_High excluding bone (PTV-bone) were compared between the algorithms. Results Dose to 95% of PTV_High with LBTE was on average 1.1 Gy/1.7% lower than with Type-B (95%CI 1.5–1.9%, p < 0.0001). This magnitude was inversely linearly correlated with the relative volume of the PTV_High containing bone (pearson r = −0.81). Dose to 98% of the GTVp was 0.9 Gy/1.3% lower with LBTE compared with Type-B (95%CI 1.1–1.5%, p < 0.05). Dose to 98% of Mand ∩ PTV was on average 3.4 Gy/5.0% lower with LBTE than with Type-B (95%CI 4.6–5.4%, p < 0.0001). Conclusion In OPC treated with IMRT, D m results in significant red...