ESTRO 38 Abstract book

S655 ESTRO 38

nasopharynx tumor were classified according to World Health Organization (WHO) classification (2005): I type 4 pts (10%), II type 19 pts (47%) and III type 4 pts (10%). IMRT prescription dose was 54-60 Gy (elective irradiation of the neck and macroscopic disease), PT prescription dose was 10-20 Gy Relative Biological Effectiveness (RBE), for a total dose up to 70-74 Gy RBE. Local control (LC) and toxicity profile (according to Common Terminology Criteria Adverse Events -CTCAE V4.03- scale) were evaluated Results Twenty-three pts (56%) received platinum based induction chemotherapy, 39 pts (95%) received concurrent chemoradiation therapy. The median follow-up was 12 months, (range, 4-57). Treatment was well tolerated, 11 (27%) pts developed grade 3 acute radiation-related toxicity: 2 pts (5%) mucositis, 1 patient (2%) skin reaction and 5 pts (12%) dysphagia. No pts had high grade (grade 3- 4) late toxicity. Grade 2 late toxicity was xerostomia found in 12 (29%) pts. Two pts (5%) developed G1 brain radionecrosis at 14 and 16 months after the end of the treatment, respectively, in both cases it was resolved at least follow-up. LC was 83%. Four pts had local recurrence at 12, 11, 8 and 8 months after treatment, respectively. Three pts developed distant metastases at 6, 18 and 25 months after the end of the treatment. Three pts died for tumor specific-causes. Conclusion for pts with LANHC a MB approach was feasible and our results showed good short-term outcome and limited radiation-related side effects. Preliminary results are encouraging but a longer follow-up and large patient accrual are required. EP-1184 Target volume delineation for adaptive treatment in HNSCC is highly variable among experts R. Apolle 1,2 , H.P. Bijl 3 , P. Blanchard 4 , A. Laprie 5 , I. Madani 6 , A. Ruffier 4 , W. Van Elmpt 7 , E.G.C. Troost 1,2,8,9,10 1 OncoRay – National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus- Technische Universität Dresden- Helmholtz-Zentrum Dresden - Rossendorf, Dresden, Germany ; 2 Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiooncology – OncoRay, Dresden, Germany ; 3 University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands ; 4 Gustave Roussy Cancer Campus, Department of Radiation Oncology, Villejuif, France ; 5 Institut Claudius Regaud, Department of Radiotherapy, Toulouse, France ; 6 University Hospital Zürich, Department of Radiation Oncology, Zürich, Switzerland ; 7 Maastricht University Medical Centre, GROW – School for Oncology and Developmental Biology- Department of Radiation Oncology Maastro, Maastricht, The Netherlands ; 8 Faculty of Medicine and University Hospital Carl Gustav Carus- Technische Universität Dresden, Department of Radiotherapy and Radiation Oncology, Dresden, Germany ; 9 German Cancer Consortium DKTK, Partner Site Dresden- and German Cancer Research Center DKFZ- Heidelberg, Dresden, Germany ; 10 National Center for Tumor Diseases NCT, Partner Site Dresden- German Cancer Research Center DKFZ- Heidelberg- Faculty of Medicine and University Hospital Carl Gustav Carus- Technische Universität Dresden- and- Helmholtz Association / Helmholtz-Zentrum, Purpose or Objective Inter-observer variability (IOV) in target volume delineation is a well-documented phenomenon and a major source of uncertainty in radiation treatment (RT) planning. The increasing adoption of adaptive RT adds a dynamic component to IOV, which is largely unknown. We analysed IOV in the pre- and mid-treatment (PT and MT) setting using expert primary gross tumour volume (GTV)

was no difference in the characteristics of demography, tumor burden (according to the 7th edition AJCC stage), and treatment. The same dose schedule, according to our SNI policy, was applied regardless of HPV status: 66~68.4 Gy in 30 fractions to the gross tumor volume (GTV); 60 Gy in 30 fractions to the high-risk clinical target volume (HR- CTV) that included immediately adjacent lymphatic level; and 36 Gy in 18 fractions to the low-risk CTV (LR-CTV) that included 1 additional lymphatic level, respectively. Results The median follow-up period was 35 (3~120) months. Grade ≥3 mucositis, dermatitis, weight loss, and soft tissue necrosis developed in 35 (16.4%), 7 (3.3%), 14 (6.5%), and 11 patients (5.1%), respectively, with no difference according to HPV status. The 3-year rates of locoregional control (LRC), distant control (DC), and overall survival (OS) of all patients were 91.7%, 89.6%, and 89.1%, respectively. HPV+ patients achieved significantly better LRC (93.3% vs. 78.6%, p=0.013), but no difference was apparent in DC (89.1% vs. 85.8%, p=0.542) and OS (90.6% vs. 81.6%, p=0.110), respectively. Among 14 patients who developed regional failure, the failure sites in relation to the target volume were inside the GTV/HR- CTV in 11 (78.6%), both inside and outside the GTV/HR- CTV in two (14.3%), and outside the GTV/HR-CTV in one (7.1%), respectively. Conclusion Based on favorable LRC in HPV+ patients with the equivalent acute side effect profile, coupled with infrequent outside the GTV/HR-CTV failure, the current SNI policy seems successful, both in HPV+ and HPV- patients, and additional effort to improve LRC in HPV- patients may be necessary. EP-1183 Proton therapy boost in locally advanced head and neck cancer: toxicity and clinical outcome E. D'Ippolito 1 , B. Vischioni 1 , M. Bonora 1 , S. Ronchi 1 , V. Vitolo 1 , D. Alterio 2 , M.R. Fiore 1 , R. Petrucci 1 , A. Iannalfi 1 , A. Barcellini 1 , A. MIrandola 3 , E. Mastella 1 , G. Magro 1 , G. Viselner 4 , A. Facoetti 1 , M. Ciocca 1 , L. Preda 4 , M. Krengli 5 , G. Ivaldi 6 , P.F. Franco 7 , U. Ricardi 7 , M.F. Palazzi 8 , B.A. Jereczek-Fossa 2,9 , F. Valvo 1 , R. Orecchia 1,2 1 National Center of Oncological Hadrontherapy, Radiotherapy Unit, Pavia, Italy ; 2 European Institute of Oncology, Division of Radiation Therapy, Milan, Italy ; 3 National Center of Oncological Hadrontherapy, Radiation therapy Unit, Pavia, Italy ; 4 National Center of Oncological Hadrontherapy, Diagnostic Imaging Unit, Pavia, Italy ; 5 University Hospital- Novara, Division of Radiation Oncology, Novara, Italy ; 6 ICS Maugeri Pavia, Unit of Radiation Oncology, Pavia, Italy ; 7 University of Turin, Department of Oncology- Radiation Oncology, Turin, Italy ; 8 Niguarda Ca' Granda Hospital, Unit of Radiotherapy, Milan, Italy ; 9 University of Milan, Department of Oncology and Hemato-oncology, Milan, Italy Purpose or Objective evaluation of feasibility, acute toxicity and early clinical outcome in patients (pts) with locally advanced head and neck cancer (LAHNC) treated with exclusive sequential mixed beam (MB) approach: intensity modulated radiation therapy (IMRT) followed by proton therapy (PT) boost on high risk areas. Material and Methods between July 2012 to January 2018, 41 pts (29 male,12 female), median age 51 years (range, 18-74), with histologically proven LAHNC (stage III and IV) were treated using a MB approach: IMRT of the neck and macroscopic disease, followed by PT boost on the pre- treatment macroscopic disease. Tumor sites were: nasopharynx 28 pts (69%), oropharynx 5 pts (12%), larynx 1 patient (2%), sinonasal 4 pts (10%) and oral cavity 3 pts (7%). The histology was: squamous cell carcinoma for 11 pts (28%), neuroendocrine tumor for 2 pts (5%);