ESTRO 36 Abstract Book

S316 ESTRO 36 _______________________________________________________________________________________________

3 University Hospitals Leuven, Radiation Oncology, Leuven, Belgium 4 CHU-UCL Namur, Radiation Oncology, Namur, Belgium 5 Institut Bordet, Radiation Oncology, Brussels, Belgium 6 University Hospital Belgium, Radiation Oncology, Brussels, Belgium 7 Ghent University Hospital, Radiation Oncology, Ghent, Belgium Purpose or Objective To identify patient-related factors, treatment-related factors, genetic variations and dosimetric parameters associated with radiation-induced late dysphagia and xerostomia after (chemo)radiation for head-and-neck cancer (HNC). Material and Methods Late dysphagia and xerostomia were prospectively scored in 3 prospective academic trials at 6, 12, 18 and 24 months after (chemo)radiation using RTOG/EORTC and CTCAE- scales in 306 HNC patients. Moderate late dysphagia and xerostomia were defined as ≥1 event of grade 2; severe late dysphagia or xerostomia were defined as ≥1 event of grade 3 or ≥2 events of grade 2. Minimal (D 98 ) and maximal (D 2 ) dose, mean (D mean ) and median dose (D 50 ) and volume receiving > 50 Gy (V 50 ) for the upper, middle and lower constrictor muscles and esophagus and D mean and V 27 for the parotid glands were derived from dose-volume data. Patient and clinical characteristics included gender, age, smoking status, pack-years, drinking habits, drinks/week, tumor site, T- stage, N-stage, chemotherapy, surgery, neck dissection, radiotherapy modality, tumor dose, fractionation, overall treatment time and baseline and acute dysphagia. Genotyping was performed using restriction length polymorphism or high resolution melting. Univariate association between non-genetic variables and radiation toxicity was assessed using Mann-Whitney-U-test or chi- square-test. Association tests for genetic variants were done by logistic regression. Results Advanced T-stage, concomitant chemoradiation and grade 3 acute dysphagia are significantly associated with the development of moderate late radiation-induced dysphagia; advanced T-stage and grade 3 acute dysphagia are significantly associated with severe late radiation- induced dysphagia. The D 2 , D 98 , V 50 , the D mean and D 50 to the pharyngeal constrictor muscles and upper esophagus correlated significantly with late dysphagia. Prediction factors for late moderate and severe xerostomia were female gender, oral cavity/oropharynx primary site and absence of surgery. The D mean and V 27 to the parotid glands were also correlated with late xerostomia. Carriers of the variant A-allele of rs1800629 G>A (TNFα) show a higher risk for developing late dysphagia and xerostomia. For xerostomia this association remains statistically significant after multivariate analysis. Conclusion Besides well-known non-genetic factors, we identified genetic variation in TNFα associated with late dysphagia and xerostomia after (chemo)radiation for HNC. PO-0606 Mandible osteoradionecrosis in oropharynx carcinoma treated with IMRT: Smoking and tumor size matter F. Caparrotti 1 , S.H. Huang 1 , Y. Song 2 , S. Bratman 1 , J. Ringash 1 , A. Bayley 1 , M. Giuliani 1 , J. Kim 1 , J. Waldron 1 , A. Hansen 3 , L. Tong 1 , W. Xu 2 , B. O'Sullivan 1 , R. Wood 4 , A. Hope 1 1 Princess Margaret Cancer Centre, Radiation Oncology, Toronto, Canada 2 Princess Margaret Cancer Centre, Biostatistics, Toronto, Canada 3 Princess Margaret Cancer Centre, Medical Oncology, Toronto, Canada

4 Princess Margaret Cancer Centre, Dental Oncology, Toronto, Canada Purpose or Objective Osteoradionecrosis (ORN) of the mandible is a late toxicity affecting patients treated with radiotherapy for head and neck malignancies. There is no standardized grading system for ORN and its reporting is based on retrospective findings in heterogeneous patient populations. The rate of ORN in the intensity-modulated radiotherapy (IMRT) era is still unknown. Material and Methods We report our institutions incidence of ORN from prospectively collected data of 1223 patients diagnosed with squamous cell carcinoma of the oropharynx (OPC) treated with curative intent IMRT, with or without concomitant systemic treatment, from January 2005 to December 2014. Clinical and dosimetric comparisons were carried out between patients with ORN and a matched control cohort of non-ORN patients. Results The rate of ORN of the mandible was 3% at 1 year, 5% at 3 years, and 8% at 5 years. On multivariate analysis (MVA), smoking (HR 1.92, 95%CI 1.09-3.4; p=0.025) and T category (HR 1.23, 95%CI 1.05-3.16; p=0.033) were statistically significant risk factors. The presence of cardiovascular comorbidities, use of bisphosphonates and pre-IMRT dental extractions were found to be statistically significant differences between our matched cohorts. Mandibular V50(cc) and V60(cc) were predictive of ORN on MVA. Conclusion Smoking cessation would likely reduce the incidence of ORN. Aside from the commonly used dose constraint of maximum dose to the mandible, minimizing V50(cc) and V60(cc) should be integrated in IMRT planning optimization. PO-0607 Quality of life and xerostomia with IMRT versus 3D-CRT in postoperative head and neck radiotherapy H.P. Van der Laan 1 , H.P. Bijl 1 , J.G.M. Vemer-van den Hoek 1 , R.J.H.M. Steenbakkers 1 , D.H.F. Rietveld 2 , M.R. Vergeer 2 , C.R. Leemans 2 , J.A. Langendijk 1 1 University of Groningen- University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands 2 VU Medical Center, Department of Radiation Oncology, Amsterdam, The Netherlands Purpose or Objective With the introduction of IMRT in head and neck cancer (HNC) a more conformal delivery of dose to the target volumes was possible. A number of randomized studies reported on the added value of IMRT versus 3D-CRT regarding xerostomia, but these studies mainly included patients treated with primary (chemo) radiation. Comparisons between IMRT and 3D-CRT after postoperative radiotherapy (PORT) are very limited. Therefore the purpose of this study was to compare patient reported global quality of life (QOL), swallowing problems, xerostomia and sticky saliva at 6 months and 12 months after PORT with IMRT relative to 3D-CRT. Material and Methods We performed a retrospective analysis on prospective collected data among 275 HNC patients who received PORT for squamous cell head and neck cancer. Patients were treated at the VUMC (n=132) between August 1999 and September 2003 and at the UMCG (n=143) between May 2007 and February 2015. None of the patients received postoperative chemoradiation. All patients completed the EORTC core quality of life questionnaire (QLQ-C30) and the module for head and neck cancer patients (QLQ-H&N35) prior to RT (baseline) and at 6 and 12 months after completion of PORT. The raw component