ESTRO 2020 Abstract book

S488 ESTRO 2020

thermoplastic masks covered by flexible coils were used. Dedicated questionnaires were completed by each patient to screen for MR-eligibility (10 questions) and document feasibility and comfort (15 questions, score 0-10 “very negative” – “very positive”). MLC based step-and-shoot IMRT was performed with the MRIdian inverse treatment planning system (Viewray). Nine to eleven fields per plan were used with a total number of segments ranging from 80 to 120. All plans were verified on a Delta4 phantom (ScandiDos) prior to treatment using a gamma analysis with a 2%/2mm dose difference and distance to agreement. Results All five patients completed treatment including MR- simulation, daily image guidance and weekly offline plan- adaptation without break or delay. The mean gamma score for adaptive replanning was 98.3% ± 2.1 %. Median time for each fraction amounted to 30 minutes, including 5 minutes (+/- 1) for set up and 11 minutes (+/- 2) for beam delivery. No patient scored the overall experience of the comfort questionnaire less than 7/10. A prospective trial protocol including weekly plan-adaptation, daily MR-image guidance, 3mm CTV to PTV margins, and salivary flow measurements was developed. The primary endpoint of this study is to reduce the rate of radiation-induced xerostomia of grade 2 or worse, 12 months after treatment from 38% (landmark IMRT data) to 20% or less. The protocol has been recently approved by the institutional review board and can be found under the ClinicalTrials.gov identifier: NCT03972072. Conclusion Normofractionated head and neck radiotherapy over 6-7 weeks implementing flexible coils over thermoplastic masks, daily MR-image guidance, and weekly MRI-guided adaptive re-planning is feasible and is associated with good comfort for the patients. The MARTHA-trial is the first prospective protocol for head and neck cancer patients to explore possible benefits of MRI-guided adaptive radiotherapy in terms of toxicity PO-0819 Repeated short-course radiotherapy regimen in elderly patients with advanced head and neck cancer M. Ferro 1 , G. Macchia 1 , A. Re 1 , A. Ianiro 2 , M. Boccardi 1 , C. Romano 2 , V. Picardi 1 , M. Ferioli 3 , A. Arcelli 3 , A. Zamagni 3 , S. Cammelli 3 , S. Mignogna 4 , M. Ferro 1 , M. Missere 5 , M. Buwenge 3 , C. Pozzo 4 , S. Cilla 2 , V. Valentini 6 , A.G. Morganti 3 , F. Deodato 1 1 Università Cattolica del Sacro Cuore, Radiation Oncology Department- Fondazione di Ricerca e Cura "Giovanni Paolo II", Campobasso, Italy ; 2 Università Cattolica del Sacro Cuore, Medical Physics Unit- Fondazione di Ricerca e Cura "Giovanni Paolo II", Campobasso, Italy ; 3 University of Bologna- S. Orsola-Malpighi Hospital, Radiation Oncology Center- Dept. of Experimental- Diagnostic and Specialty Medicine – DIMES, Bologna, Italy ; 4 Università Cattolica del Sacro Cuore, Oncology Department- Fondazione di Ricerca e Cura "Giovanni Paolo II", Campobasso, Italy ; 5 Università Cattolica del Sacro Cuore, Radiology Department- Fondazione di Ricerca e Cura "Giovanni Paolo II", Campobasso, Italy ; 6 Università Cattolica del Sacro Cuore- Policlinico Universitario “A. Gemelli”, Radiotherapy- Radiology and Hematology Department – Gemelli ART Advanced Radiation Therapy, Roma, Italy Purpose or Objective To assess the feasibility and safety of a repeated SHort- course Accelerated RadiatiON therapy (SHARON) regimen in the palliative setting of Head and Neck (H&N) locally advanced or metastatic cancer in elderly patients. Material and Methods Patients with histological confirmed H&N cancers, age ≥ 80 years, expected survival > 3 months and Eastern Cooperative Oncology Group (ECOG) performance status of ≤ 3 entered the study. Patients were treated in cohorts of six patients: a total dose of 20 Gy was delivered in 2

PO-0817 Implication of BRAF mutations in well- differentiated thyroid carcinoma. J.A. Dominguez Rullan 1 , R. Hernanz Lucas 2 , C. Vallejo Ocaña 2 , M. Martín Martín 2 , S. Sancho García 2 1 Hospital Universitario Ramón y Cajal, Radiation Oncology, Boadilla del Monte, Spain ; 2 Hospital Universitario Ramón y Cajal, Radiation Oncology, Madrid, Spain Purpose or Objective Differentiated thyroid cancer has an excellent prognosis and can be successfully treated with surgery, radioiodine ablation and thyroid suppression therapy. However, tumor recurrence occurs in 7-20% of patients. The BRAF V600E mutation is the most common genetic alteration and occurs in approximately 45-50% of patients and the presence of this mutation has been related with worst prognosis and response to radioiodine ablation and more advanced disease at diagnosis. The purpose of this study was to evaluate the results of loco-regional advanced PTC treated with adjuvant radiotherapy and the impact of BRAF status in clinical outcomes. Material and Methods Between 2007 and 2015, 24 patients with PTC were treated in our institution with adjuvant RT after surgery and radioiodine ablation for pT4 disease or/and positive surgical margins. We assessed BRAF status in FNA biopsy and pathology in thyroidectomy specimen. Overall survival (OS) and progression-free survival (PFS) were calculated using de Kaplan-Meier and patterns of recurrence were reported. Results Mean age at diagnosis was 64 years (43-85). Sixteen patients were PTC (papillary thyroid cancer), seven FTC (follicular thyroid cancer) and one Hurthle cell carcinoma. Most patients were treated with total thyroidectomy (95.9%) and lymph node dissection was developed in 70.8% of patients (central-compartment neck dissection in 83.4% and lateral neck dissection in 29.2%). There were 13 patients pT3 and 10 patients pT4a and N stage was pN0 in 3 patients, pN1a in 11 and pN1b in 6. 68.2% and 13.6% of patients had microscopic and macroscopic residual disease, respectively. BRAF mutation was seen in 9 of 12 patients with molecular testing. Radioiodine ablation and adjuvant EBRT was used in all patients. Mean RT dose was 62.4 Gy (60-70 Gy). Regional recurrence was seen in 13% and distant metastasis in 42.9% of patients, no local relapse was observed. Mean follow-up was 49 months. 3- year OS was 80.2% and 3-year PFS was 67.3%. No significant differences in distant metastasis or regional relapse were found in patients who carried BRAF V600E mutation in our series. Conclusion In our series BRAF V600E mutation was not related with poorer outcomes in locally advanced thyroid carcinoma although it could be useful to select patients that may benefit from more intensive treatment. PO-0818 Feasibility and first experience of MR-guided adaptive radiotherapy for head and neck cancer P. Balermpas 1 , J. Krayenbühl 1 , M. Chamberlain 1 , M. Bogowicz 1 , H.I. Garcia-Schüler 1 , N. Andratschke 1 , A.K. Moreira 1 , L. Wilke 1 , S. Tanadini-Lang 1 , M. Guckenberger 1 1 University Hospital Zurich, Radiation-Oncology, Zurich, Switzerland Purpose or Objective To demonstrate feasibility and provide the first prospective clinical protocol for MR-Linac-guided, adaptive IMRT for patients treated with bilateral radiotherapy for head and neck cancer. Material and Methods Five patients with curative intended primary, bilateral radiotherapy for head and neck cancer have been treated as pilot patients at the MRIdian platform. Standard