ESTRO 2020 Abstract book

S20 ESTRO 2020

All radiotherapy departments in this national study were invited to complete an online survey and submit OAR contours for five HNC cases. Reference contours were delineated using the guidelines and compared to the contours from the different radiotherapy departments using DICE similarity coefficients (DSC) and median Hausdorff distances (HD50). Results Fourteen of 22 centres (64%) completed the survey and delineations. Thirteen centres used delineation guidelines and six confirmed the use of guidelines of Brouwer et al. Table 1 shows the median (and range) DSC and HD50 for all OARs in all five patients. The OARs that were delineated best were the mandible and brainstem followed by the parotid glands and submandibular glands. Table 1 also shows the number of times OARs were delineated. The supraglottic larynx was delineated least often (20 times) and the left parotid gland most often (62 times). Figure 1 shows DSC for every delineated OAR compared to the reference contour and the corresponding HD50. This figure shows that DSC and HD50 are negatively related and that there is clearly more IOV in some OARs compared to others. Especially cochlea’s, upper oesophagus, PCMs, supraglottis, and glottic area did poorly.

Conclusion Delineation is a crucial step in radiotherapy and OARs should be delineated properly to allow correct evaluation of treatment plans. Furthermore, the importance of correct delineation increases with increasing accuracy of radiotherapy. With this national study we have shown that despite availability of international consensus guidelines, these are not widely implemented which could explain the large IOV in multiple OARs. This study highlights the need to further promote guidelines, to reduce IOV and benefit from more accurate radiotherapy techniques. PD-0053 Swallowing outcomes in re radiation for second primary and recurrent head neck cancers C. Johnny 1 , S. Ghosh Laskar 1 , A. Budrukkar 1 , N. Mummudi 1 , M. Swain 1 1 Tata Memorial Center, Radiation Oncology, Mumbai, India Purpose or Objective Re irradiation (Re RT) in recurrent/ second primary head neck cancers has been used judiciously and have varied success. Complication rates after Re RT vary from 7% to 50% with increased complications when the target is in close proximity to critical organs. In patients receiving Re RT for head neck cancer, aggressive treatment can significantly affect breathing, swallowing, speech or physical appearance. In patients receiving Re RT, Quality of life (QOL) related to swallowing is already impaired due to prior therapies and there is a paucity of data regarding swallowing outcomes, dose constraints and prognostic factors for morbidity. The aim of the current prospective study is to co-relate the dosimetric variables with clinical and QOL outcomes. Material and Methods Consecutive patients of recurrent or second primary head neck cancers planned for Re RT were accrued in the study. Standard treatment protocols for Re RT were followed that included a detailed history, clinical examination and documentation of functional, swallowing status. Swallowing function was assessed subjectively using the EORTC QLQ C30, HN35 questionnaire while objective assessment was done using Functional oral intake scale (FOIS) and Leipzig Pearson (LP) scale scored at baseline, radiotherapy conclusion and subsequent follow-ups. Standard organs at risk and Dysphagia Aspiration Related