ESTRO 36 Abstract Book

S565 ESTRO 36 2017 _______________________________________________________________________________________________

3 Oxford University NHS Foundation Trust, Department of Oncology, Oxford, United Kingdom Purpose or Objective Squamous cell carcinomas (SCC) of the oropharynx are potentially curable cancers with a combination of surgery, radiotherapy or chemoradiotherapy. Osteoradionecrosis (ORN) is a significant late side effect of radiotherapy. Recent data suggests the risk of mandible ORN increases significantly if the mean dose is >37.5Gy. The anterior mandible is an important structure for dental rehabilitation, with implants in this area regarded as the standard of care. Our study had two aims; firstly to accurately describe the dose distribution to defined areas of the mandible and maxilla in a population of oropharyngeal patients receiving radical (chemo)radiation. Secondly, to test in silico the hypothesis that it is possible to limit the dose to the anterior mandible to facilitate implant-based rehabilitation. Material and Methods All radically treated oropharyngeal patients between March 2014 and March 2015 treated at our centre were reviewed. The inclusion criteria were patients over the age of 18, with an oropharyngeal primary (tonsil or tongue base) SCC, who had treatment with primary (chemo)radiotherapy dose of 65Gy in 30 fractions and who required nodal irradiation. Only patients treated using a volumetric arc therapy dose solution were included, and static gantry IMRT was excluded. Treatment records were reviewed for patients’ characteristics including age, primary site, tumour size, nodal stage, HPV status, dentate status and use of cisplatin based chemotherapy. A published mandible and maxilla contouring atlas was used to create 6 sextant volumes; 3 in each structure. Plans were selected for replanning if the anterior mandible sextant received a mean dose of >37.5Gy. Ethical approval for the study was obtained by the West Midlands Research Ethics Committee. Radiotherapy planning was performed on Varian Eclipse RapidArc v.11 and calculated using Varian’s Analytical Anisotropic Algorithm (AAA) 10.0.28. All replans were approved by a Consultant Clinical Oncologist who specialises in Head and Neck treatment. Results 60 patients were included. Patient characteristics are outlined in Table 1 and dose metrics to each mandible sextant, by primary site, are described in Table 2. Patients who had Level I nodal irradiation received significantly higher doses to the anterior mandible (Wilcoxon rank sum, p<0.0001). 11 patients were included in the planning study as per study protocol. 91% were successfully re-optimised to a Mean Dose < 37.5Gy. Replanned patients had statistically significant increased doses in spinal cord D1cc (Wilcoxon signed rank, p = 0.005) and spinal cord PRV D1cc (Wilcoxon signed rank, p = 0.002), but remained within absolute tolerances. Other organs at risk received no statistically significant increase in dose.

The data of 21 patients with locoregionally recurrent differentiated thyroid papillary carcinoma who underwent external beam radiation therapy between 2001 and 2010 were analyzed retrospectively. External beam radiation therapy was considered for locoregional recurrence that is unresectable or with extranodal extension or involvement of soft tissues. The primary endpoint was the locoregional recurrence-free survival rate. Results The median follow-up time was 87 months (range, 38 to 173 months). Six (28.6%) patients developed treatment failure: Two (9.5%) patients had locoregional failure and 4 (19.4%) patients had distant failure. The 10- and 14-year locoregional relapse-free survival rates were 89.9% and 89.9%, respectively. The 10- and 14-year distant relapse- free survival rates were 77.3% and 51.6%, respectively. The 10- and 14-year overall survival rates were 95.2% and 71.4%, respectively. Conclusion External beam radiation therapy can achieve favorable treatment outcomes. External beam radiation therapy should be considered for locoregional recurrence that is unresectable or with extranodal extension or involvement of soft tissues. EP-1031 FDG-PET/CT as a guide for Intensity-Modulated Radiation Treatment of advanced head and neck cancer F. Ricchetti 1 , R. Mazzola 1 , S. Fersino 1 , N. Giaj-Levra 1 , A. Fiorentino 1 , U. Tebano 1 , D. Aiello 1 , R. Ruggieri 1 , F. Alongi 1 1 Sacro Cuore Don Calabria Cancer Care Center, Radiation Oncology Department, Negrar, Italy Purpose or Objective To analyze the impact of Fluorodeoxyglucose-PET/CT (PET/CT) in the radiotherapy (RT) planning-strategy in head and neck cancer, focusing on neck-nodes treatment planning and correlating CT-scan and PET/CT performances. Material and Methods Inclusion criteria of this retrospective analysis were: age > 18 years old, histologically proven squamocellular head and neck cancer, patients candidate to curative Intensity- Modulated Radiation Treatment ± chemotherapy, evaluation of stage of disease by means of PET/TC and CT- scan performed at our Institution. Results Sixty patients, treated between October 2011 and February 2016, were included in the analysis. Primary tumor site was represented as follow: Nasopharynx in 8 patients (13%), Oropharynx in 25 (42%), Oral Cavity in 19 (32%) and Larynx non-glottic in 8 (13%). Oral cavity tumors revealed to be at particular risk of nodal stage migration, occurring in 21% of cases (5/19). PET/CT findings caused changes in the management of RT volumes in 10% of patients. In one case of nasopharynx cancer, PET/CT allowed to detect the primary tumor previously unknown at CT-scan, in 5 cases of oral cavity tumors neck-nodes PET/CT positive from one side and/or the opposite (not detected at CT-scan) were included in the high-risk volume, and in 2 cases of oropharyngeal cancer RT was avoided because of distant metastases. Conclusion Present findings show that PET/CT images could be a guide in head and neck cancer in order to individualize the RT curative strategy. Further investigations are advocated to evaluate if this strategy could impact on long-term outcomes in these patients. EP-1032 Optimising head and neck radiotherapy for dental rehabilitation S. O'Cathail 1 , N. Karir 2 , K. Shah 3 1 CRUK/MRC Institute for Radiation Oncology University of Oxford, Oncology, Oxford, United Kingdom 2 Oxford University NHS Foundation Trust, Department of Dentistry, Oxford, United Kingdom