ESTRO 36 Abstract Book

S586 ESTRO 36 _______________________________________________________________________________________________

5 National Center for Tumor Diseases partner site Dresden, Dresden, Germany

Purpose or Objective To perform a dosimetric evaluation of the brachial plexus (BP) dose in locally advanced H&N cancer patients undergoing moderate hypofractionated-accelerated chemoradiation performed by a SIB-VMAT technique. Material and Methods Patients with locally advanced H&N cancer receiving induction chemotherapy (ICT) and subsequent platinum based concurrent radiotherapy were included in this retrospective analysis. Toxicity and outcomes data were recorded during the routine follow-up. In all patients, right (RBP) and left (LBP) BP were delineated according to RTOG guidelines by the same radiation oncologist. RBP and LBP mean doses, V50, V55 and V60 were recorded and correlated with late neurological toxicity. Results From July 2010 to January 2015, 50 patients [M/F: 40/10; median age: 57y, range 30-77; stage III: 11 (22%), stage IV: 39 (78%)] were treated and represent the object of the analysis. ORL subsites were as follows: oropharynx (22; 44%), epipharynx (8;16%), oral cavity (9; 18%), larynx (4; 8%) and hypopharinx (7; 14%). Cisplatin plus 5-fluorouracil chemotherapy schedule was administered as ICT in 72% of cases, while 22% of patients received a 3-drugs protocol (cisplatin, 5-fluorouracil and docetaxel). A moderate accelerated hypofractionation was delivered by using a 2 arc SIB-VMAT technique. Doses to macroscopic disease (T and N) ranged from 67.5/2.25 Gy (8 patients; 16%) to 70.5/2.35 Gy (42 patients; 84%), while the high and low risk nodal areas received 60/2 Gy/die and 55.5/1.85 Gy in 30 fractions, respectively. As per DVH analysis, LBP and RBP mean dose were 48.4 Gy and 48 Gy, V50 were 68.5% and 68.9%, V55 were 56.1%and 58.9%, V60 were 28% and 32.6%, respectively. In 44% of cases part of the LBP was included within the high dose PTV (67.5Gy in 12% and 70.5 Gy in 32% of patients). Conversely, in 46% of cases part of the RBP was included within the high dose PTV (67.5Gy in 8% and 70.5 Gy in 38% of patients). With a median follow- up of 19 months (range 3-53) no symptoms of brachial plexopathy were reported, although in 87% of cases doses to BP exceeded the suggested literature constraint of 60 Gy. Conclusion A SIB-VMAT moderate accelerated hypofractionation at the doses reported in this analysis seems to be tolerable and safe, without cases of neurological toxicity. Longer follow-up and further prospective studies in larger series are warranted to confirm these findings. EP-1067 is adenoid cystic carcinoma (ACC) radioresistant?: the effect of radiotherapy for ACC of head and; neck I. Jung 1 , J. Kim 1 , S. Ahn 1 , S. Song 1 , S. Yoon 1 , S. Kim 1 , J. Park 1 , E. Choi 1 , S. Lee 1 1 Asan Medical Center- Univ of Ulsan, Radiation oncology, Seoul, Korea Republic of Purpose or Objective The adenoid cystic carcinoma (ACC) of head and neck showed insidious onset and usually advanced at initial presentation. Because of limitation of anatomy of head and neck, in some cases, wide excision may not be possible. And even further, in other cases surgical excision may not be possible. Therefore we evaluated efficacy and safety of definitive radiation therapy in head and neck ACC. Also, we analyzed prognostic factors in adjuvant radiation therapy of it. Material and Methods From January 1995 to December 2013, 94 patients received radiotherapy for head and neck adenoid cystic carcinoma in Asan medical center. Fourteen patients were excluded because of systemic metastasis (n=7), other primary cancer (n=3), incomplete RT (n=2), and previous

Purpose or Objective Radiochemotherapy (RCT) for patients with head and neck squamous cell carcinoma (HNSCC) frequently causes xerostomia and dysphagia, which may be alleviated by treatment adaption, e.g., modulation of dose distribution to the salivary glands. Current clinical models, which are based on dosimetric parameters, mostly achieve moderate prediction accuracy. Therefore, we aimed to improve the prediction of xerostomia and dysphagia by using additional imaging biomarkers based on computed tomography (CT) scans. Material and Methods In this study 46 patients with UICC stage III/IV advanced head and neck squamous cell carcinoma (HNSCC) were considered (NCT00180180, [1]). All patients received primary RCT and underwent a pre-treatment CT scan without intravenous contrast agent. Patient-reported xerostomia and dysphagia were evaluated at baseline, every week during RCT, four weeks after treatment and three monthly thereafter. 5040 imaging features were extracted from the parotid and submandibular glands. Feature reproducibility tests based on the RIDER re-test data set [2] were performed leading to 1513 imaging features in total. The most informative features were selected by a univariate logistic regression analysis. The developed radiomic signature was used to train and validate multivariate logistic regression and random forest models using repeated 5-fold cross validation. The predication accuracy was assessed by the area under the curve (AUC). Results The logistic regression and the random forest model achieved similar performance in predicting xerostomia (AUC=0.71). The developed signature consisted of one dosimetric parameter and one imaging feature. For the prediction of dysphagia both models achieved only a moderate prediction accuracy (AUC=0.55). Conclusion For prediction of xerostomia, a signature was developed and showed a good performance. For dysphagia only moderately performing models could be obtained in this cohort. Based on our results, subgroups of patients at a high risk of xerostomia may be identified and offered treatment adaption. However, further investigations are currently ongoing, i.e., externally validating the developed signature, which is an important step in developing clinically relevant prediction models. EP-1066 Hypofractionated accelerated SIB-VMAT radiotherapy for H&N cancer: brachial plexus constraint M. Nuzzo 1 , L.P. De Vivo 1 , F. Deodato 1 , G. Macchia 1 , M. Ferro 1 , M. Ferro 1 , L.G. Serino 1 , S. Cilla 2 , S. Cammelli 3 , A. Farioli 4 , A. Arcelli 3,5 , A. Veraldi 3 , G.P. Frezza 5 , V. Valentini 6 , A.G. Morganti 3 1 Fondazione di ricerca e cura "Giovanni Paolo II", Radiotherapy Unit, Campobasso, Italy 2 Fondazione di ricerca e cura "Giovanni Paolo II", Medical Physics Unit, Campobasso, Italy 3 University of Bologna, Radiation Oncology Center- Department of Experimental- Diagnostic and Speciality Medicine - DIMES, Bologna, Italy 4 University of Bologna, Department of Medical and Surgical Sciences - DIMEC, Bologna, Italy 5 Ospedale Bellaria, Radiotherapy Department, Bologna, Italy 6 Policlinico Universitario "A. Gemelli"- Universtà Cattolica del Sacro Cuore, Department of Radiotherapy, Rome, Italy