ESTRO 2020 Abstract Book

S20 ESTRO 2020

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 Structures (DARS) were delineated on the planning CT images. Normal Tissue Complication Probability (NTCP) was calculated using biological modeling with Equivalent Uniform Dose (EUD). Results A total of 52 patients were included in the study. Oral cavity was the most common site with 45 patients (85%) and 77% of the patients had primary surgery prior to Re RT. The median Re RT dose, number of fractions and duration was 60Gy (IQR 60-64Gy), 30 (IQR 30-32) and 44 days (IQR 42-48 days) respectively. Median PTV volume was 480 (304-608.7)cc. Feeding tube was present in 54.9% and 25.2% at baseline, and first follow-up respectively. The QOL domain scores and swallowing scores are given in the table 1. The NTCP and EUD for TD 47 and TD 50 were 25.1%, 3.7% and 42Gy, 40.8Gy respectively. Logistic regression analysis showed a significant correlation of DARS V30, V40 and V50 with the presence of feeding tube at first follow-up. There was also a significant correlation between the DARS V30, V40, V50, mean dose and PTV volume with the first follow-up HNSW QOL score.

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