ESTRO 2023 - Abstract Book

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ESTRO 2023

was 54 months (95%CI: 36–72 months) for p16- patients. Median survival was not reached for p16+ patients. Stage predited for recurrence (p<.0005) but not survival. Use of concomitant chemotherapy did not predict recurrence (p=.748) or survival (p=.550). On univariate analysis, both primary and nodal GTV predicted for overall survival (HRs (CI): 1.039 (1.023 - 1.054) and 1.007 (1.002 - 1.012), respectively). On multivariate analysis, primary GTV remained significant in predicting survival (HR: 1.036, CI 1.019 - 1.052).

Conclusion Primary GTV predicts overall survival in patients with OPSCC treated with RT. This is a measure readily available to Radiation Oncologists at treatment planning, and in the future may aid treatment de-escalation decision making. Further work is needed to identify patients for whom RT can be safely de-escalated, to reduce long term treatment morbidity. References: Adrian, G., Carlsson, H., Kjellén, E. et al. Primary tumor volume and prognosis for patients with p16-positive and p16 negative oropharyngeal squamous cell carcinoma treated with radiation therapy. Radiat Oncol 17, 107 (2022).

PO-1176 Aspiration and painful swallowing: relation to swallowing muscles and inferior brainstem dose

W. Heemsbergen 1 , L. Kramer 2 , N.D. Sijtsema 2 , G.M. Verduijn 2 , S.F. Petit 2 , J. Elbers 2

1 Erasmus MC Cancer Institute, University Medical Center Rotterdam, Dept. of Radiotherapy, Rotterdam, The Netherlands; 2 Erasmus MC Cancer Institute, University Medical Center Rotterdam, Dept of Radiotherapy, Rotterdam, The Netherlands Purpose or Objective Dysphagia is defined as difficulty in swallowing and/or altered eating, and often used as endpoint in NTCP modelling. Swallowing muscles have been described in literature as relevant organs at risk (OAR) and recently, dose to the inferior brainstem (where the swallowing center is located) has been suggested as a relevant OAR for dysphagia. However, underlying problems of dysphagia vary and can be caused by e.g. painful swallowing, aspiration, dry mouth, oral pain, passage difficulties, appetite/taste loss, dental problems, and/or trismus. Therefore, it is important to use more specific definitions for NTCP evaluations than the broad definition of dysphagia. So, we studied the relationship between late painful swallowing, aspiration, and dose to potential OARs. Materials and Methods From a retrospective cohort of oropharynx patients treated (2010-2015) with definitive (chemo)radiotherapy and disease free >1 year post-RT (n=254), we randomly selected 25 control cases without dysphagia complaints at one year (CONTR group), 25 cases with aspiration at one year (ASP group), and 25 cases with painful swallowing at one year (PSWAL group). For N=71 CT scans with dose distributions were available and OARs (swallowing muscles, inferior brainstem) were delineated. Mean dose ( α / β =3) to OARs were compared between case and control group. The hypothesis of a higher mean dose in the OAR for the cases vs controls was tested (t-test, one-sided p).

Results