ESTRO 2020 Abstract Book

S13 ESTRO 2020

(p=0.029 and 0.037) as well as constraint-violations to the optic nerve (p=0.002 and <0.001). Pituitary toxicity: Six patients (22%) had abnormal hormonal functioning in the gonadal-, and the thyroid axis, but no dose-response correlation was detected. One patient exhibited pan- hypopituitarism and substitutional therapy was initiated. Olfactory function: Sixteen patients (59%) had age- adjusted impaired olfactory function, which was worse in patients who underwent surgery compared with those treated with IMRT alone (p=0.01). Diffusion MRI: Voxel-by- voxel analyses on several functional diffusion parameters and analyses of atrophy and dose-distribution will be undertaken. Patient reported outcomes: In the global quality of life analysis, the most affected domains were social and emotional functions, while fatigue and insomnia were the most severely reported symptoms. Conclusion We found substantial long-term morbidity after radiation therapy for SNC across different organs at risk. Based on the current findings, a nationwide prospective registration of morbidity following treatment for SNC has been initiated by the Danish Head and Neck Cancer (DAHANCA) group, and a prospective trial of proton therapy for sinonasal cancer is currently being implemented (DAHANCA36b). PH-0042 Aspiration related OARs are relevant predictors of silent aspiration after (chemo)radiation. A. Gawryszuk 1 , H.P. Van der Laan 1 , R.J.M. Steenbakkers 1 , J.G.M. Van den Hoek 1 , M. Holwerda 2 , I.M. Verdonck-de Leeuw 3 , R.N. Rinkel 3 , H.P. Bijl 1 , J.A. Langendijk 1 1 University Medical Center Groningen- Groningen, Department of Radiation Oncology, Groningen, The Netherlands ; 2 University Medical Center Groningen- Groningen, Department of Otolaryngology- Speech Language Pathology, Groningen, The Netherlands ; 3 Amsterdam University Medical Center, Department of Otolaryngology – Head & Neck Surgery, Amsterdam, The Netherlands Purpose or Objective Late (silent) aspiration, potentially leading to pneumonia, is one of the most hazardous complications after (chemo)radiation ((CH)RT) for head and neck cancer. Due to its silent nature, it can only be captured during objective examination. Videofluoroscopy (VF) is the golden standard. Radiation dose to the supraglottic larynx is known to be associated with aspiration, but the role of muscular dysfunction responsible for reduced hyolaryngeal elevation (= underlying mechanism of aspiration) is not widely assessed and addressed. The purpose of this analysis was to identify the best predictors of RT-induced silent aspiration captured on VF. Material and Methods This prospective cohort study included 189 head and neck cancer patients receiving definitive (CH)RT. Patients underwent a comprehensive dysphagia assessment (including VF) at baseline and 6 months after treatment. Three primary endpoints of silent aspiration (SA) were considered at 6 months after treatment. The endpoints corresponded to aspiration with 3 different bolus viscosities: liquid (SA_LIQ), pudding (SA_PUD) and solid (SA_SOL). SA was defined as a VF-based Penetration Aspiration Scale (PAS) score 8. Swallowing structures (SWOARs) and Functional Swallowing Units (FSUs) were delineated according to published and/or international consensus guidelines (Brouwer et al. 2015, Gawryszuk et al. 2019). Baseline features relevant for SA and average doses (D mean ) of all delineated structures were selected as candidate variables. Multivariable normal tissue complication probability (NTCP)-models were developed using logistic regression with bootstrapping, dealing with non-linear dose-effect relations and multicollinearity. Results

The prevalence of SA_LIQ, SA_PUD, and SA_SOL were 19%, 17%, and 16%, respectively. The best performing models for the 3 endpoints included the following prognostic factors: SA_LIQ: Supraglottic Larynx (SG D mean ), Upper Esophageal Sphincter, consisting of pharyngeal constrictor inferior, cricopharyngeal muscle and esophagus inlet muscle (UES D mean ), Anterior Complex, consisting of floor of mouth and thyrohyoid muscles (AC D mean ), disease stage 3-4; SA_PUD: SG D mean , UES D mean , disease stage 3-4; SA_SOL: SG D mean , AC D mean , disease stage 3-4. All models had good calibration and model performance (apparent ROC-AUC: 0.71, 0.79 and 0.82 respectively). Table 1.

Conclusion Patients with more advanced disease are at the highest risk of silent aspiration for all bolus viscosities after (CH)RT. Beside the dose to the Supraglottic Larynx also the dose to the UES and AC (Fig. 1) contribute to a greater risk of silent aspiration. Additional sparing of the Anterior Complex could potentially reduce the risk of silent aspiration after (CH)RT for head and neck cancer.

PH-0043 Age related toxicity and outcome in oropharyngeal and nasoparyngeal cancer patients E. IvaldI 1 , G. Infante 2 , N. Facchinetti 1 , P. Bossi 3 , N.A. Iacovelli 1 , A. Cavallo 4 , R. Ingargiola 1 , L.D. Locati 5 , C. Bergamini 5 , C. Resteghini 5 , L. Licitra 5 , F. Platini 5 , G. Calareso 6 , C. Fallai 1 , E. Orlandi 7 1 Fondazione IRCCS Istituto Nazionale dei Tumori di