ESTRO 2020 Abstract book

S475 ESTRO 2020

the tongue, masseter, temporalis and pterygoid muscles. In patients with head and neck cancer (HNC), mastication may be disrupted, which can result in affected motor and oral functioning. To measure objectively the masticatory performance, the Mixing Ability Test (MAT) was developed. In this study, the test-retest reproducibility of the MAT was evaluated in patients with head and neck cancer and healthy controls, in order to make a comparison between the two groups and to calculate reference values. Material and Methods Thirty-four patients with head and neck cancer and forty two healthy controls performed the MAT twice on the same day. To assess test-retest reproducibility, the Intraclass Correlation Coefficient (ICC 2,1 ), Standard Error of Measurement (SEM and SEM%), Smallest Detectable Change (SDC and SDC%), and Limits of Agreement (LoA) were calculated. Bland-Altman plots were constructed to check for systematic bias, variability and agreement. Results A good (ICC =0.886) and a moderate correlation (ICC = 0.525) were found for patients and healthy controls, respectively. The mean test outcome for patients was 19.12, and 16.42 for healthy controls, in which a higher number corresponds to a worse mixing ability. The SEM was 0.76 (4%) for patients, and 1.45 (9%) for healthy controls, with a SDC of 2.12 (11.1%) and 4.02 (24.8%), respectively. The LoA were -4.46 to 4.42 for patients, and -3.65 to 4.59 for healthy controls.

Conclusion Patients with HNC perform significantly worse on the MAT in comparison to healthy controls. The MAT has a good reproducibility in patients with head and neck cancer and a moderate reproducibility in healthy controls. The SDC and SDC% values will be useful for clinicians and researchers to determine whether an oncological treatment or rehabilitation has an actual effect on the masticatory performance of patients. PO-0793 Does delivered OAR dose improve prediction of late toxicity in head & neck cancer patients? D. Noble 1 , K. Harrison 2 , L.E.A. Shelley 3 , A.M. Bates 4 , J.E. Bailey 5 , M.Z. Wilson 6 , M. Romanchikova 7 , S.J. Thomas 8 , A. Hoole 8 , R. Jadon 9 , G.C. Barnett 9 , R.J. Benson 9 , S.J. Jefferies 9 , N.G. Burnet 10 , R. Jena 1 1 University of Cambridge, Oncology, Cambridge, United Kingdom ; 2 University of Cambridge, Cavendish Laboratory, Cambridge, United Kingdom ; 3 Western General Hospital, Edinburgh Cancer Centre, Edinburgh, United Kingdom ; 4 Cambridge University Hospitals NHS Foundation Trust, Cambridge Clinical Trials Centre- Box 279, Cambridge, United Kingdom ; 5 Cheltenham General Hospital, Gloucestershire Oncology Centre, Cheltenham, United Kingdom ; 6 University College London, Department of Medical Physics and Biomedical Engineering, London, United Kingdom ; 7 National Physical Laboratory, Data Science Team, Teddington, United Kingdom ; 8 Cambridge University Hospitals NHS Foundation Trust, Department of Medical Physics and Clinical Engineering, Cambridge, United Kingdom ; 9 Cambridge University Hospitals NHS Foundation Trust, Oncology Centre, Cambridge, United Kingdom ; 10 University of Manchester, Manchester Academic Health Science Centre and The Christie NHS Foundation Trust, Manchester, United Kingdom ), and adapting treatment plans mid-treatment can correct for this. However, few studies directly assess whether ART improves clinical outcomes, and none link delivered OAR dose to side effects. The purpose of this study was to establish whether planned or delivered OAR dose better predicts toxicity events, thereby providing clinical data to support ART in HNC. Material and Methods 198 HNC patients were treated with standard protocols on TomoTherapy units with daily MVCT-IG. Toxicity data were prospectively collected at baseline and 12 months. Purpose or Objective Delivered radiation dose to H&N OARs (D A ) may be different from planned dose (D P