ESTRO 36 Abstract Book

S587 ESTRO 36 2017 _______________________________________________________________________________________________

Conclusion Our data shows that IMRT-SIB with 2.25 Gy/fraction with concurrent platinum-100- based chemotherapy is a safe treatment approach without increasing toxicities. This regimen is therefore acceptable for the therapy of locally advanced oropharyngeal cancer and patients with poor prognosis as HPV negative OPSCC could benefit from it. A longer follow up is needed to fully evaluate late toxicity and survival. EP-1077 Predictive modeling for radiation-induced acute dysphagia in head and neck cancer patients. D. Alterio 1 , M. Gerardi 1 , L. Cella 2 , V. D'Avino 2 , G. Palma 2 , D. Ciardo 1 , E. Rondi 3 , A. Ferrari 1 , M. Muto 4 , R. Spoto 4 , R. Pacelli 5 , R. Orecchia 6 , B. Jereczek 7 1 European Institute of Oncology, Radiation Oncology, Milan, Italy 2 National Council of Research, Biostructures and Bioimaging, Naples, Italy 3 European Institute of Oncology, Medical Physics, Milan, Italy 4 European Institute of Oncology - University of Milan, Radiation Oncology -Oncology and Hemato-oncology, Milan, Italy 5 Federico II- University school of Medicine, Advanced Biomedical Sciences, Naples, Italy 6 European Institute of Oncology - University of Milan, Medical Imaging and Radiation Sciences - Oncology and Hemato-oncology, Milan, Italy 7 European Institute of Oncology - University of Milan, Radiation Oncology - Oncology and Hemato-oncology, Milan, Italy Purpose or Objective To explore dosimetric predictors of acute dysphagia in head and neck (H&N) cancer patients (pts) treated with definitive radiotherapy (RT). We prospectively examined correlation between doses to swallowing-associated structures and acute radiation-related side effects, in terms of dysphagia and percutaneous endoscopic gastrostomy tube (PEG) requirement. Material and Methods We analyzed all consecutive not previously treated pts with H&N cancer who underwent RT at our Department between May 2010 and March 2011. Exclusion criteria were: baseline dysphagia (functional dysphagia or enteral nutrition) and previous surgery in the H&N region. A nutritional standardized step-wedge protocol was applied. Dysphagia (grade ≥3 according to CTCAE v4.0) and indication to PEG insertion were classified as acute toxicity events. Ten swallowing-related structures were considered for the analysis: pharyngeal axis, base of tongue, constrictor muscles (superior, middle and inferior), cricopharyngeal muscle, soft palate, cervical esophagus, oral cavity and supraglottic larynx. Dosimetric parameters included mean dose (Dmean), near maximum dose (D2%) and the percentage volume exceeding X Gy (Vx) evaluated in 5-Gy steps. The correlation of clinical information along with swallowing-related structure dose parameters related to acute toxicity events was analyzed by means of Spearman’s rank correlation coefficient (Rs). Multivariate logistic regression method using resampling methods (bootstrapping) was applied to select model order and parameters for normal tissue complication probability (NTCP) modeling. Model performance was evaluated through the area under the curve (AUC) of the receiver operating characteristic (ROC) analysis. Results Patient and treatment characteristics are summarized in Table 1. Two pts required PEG, 3 pts had grade 3 dysphagia and 4 pts had both PEG and grade 3 dysphagia. A strong multiple correlation between dosimetric parameters was found. Intra-organ dosimetric parameters were strongly correlated as well as inter-organ dosimetric parameters. Accordingly, the highly correlated variables

patients over a longer follow up before dWMRI can be utilised in clinical practice. EP-1076 toxicity of concomitant chemotherapy and IMRT in locally advanced OPSCC: sequential vs SIB technique G. Abate 1 , F. De Felice 1 , A. Galdieri 1 , G. Gravina 2 , F. Marampon 3 , D. Musio 1 , V. Tombolini 1 1 Policlinico Umberto I- “Sapienza” University of Rome, radiotherapy, Roma, Italy 2 University of L'Aquila, Department of Biotechnological and Applied Clinical Sciences- Laboratory of Radiobiology, L'Aquila, Italy 3 University of L’Aquila-, Department of Biotechnological and Applied Clinical Sciences- Laboratory of Radiobiology, L'Aquila, Italy Purpose or Objective Concurrent radiochemotherapy is the standard of care for locally advanced oropharingeal squamous cell carcinoma (OPSCC) patients. Due to a substantial locoregional recurrence rate especially in human papilloma virus (HPV) negative disease, an improvement in treatment outcome is desirable. Treatment intensification with radiation dose escalation could represent a valid option by applying accelerated radiotherapy with higher dose for fraction and non- uniform dose distribution with simultaneous integrated boost (SIB). Even if radiobiological and clinical data suggest that accelerated fractionation with higher dose per fraction given in GTV may produce better locoregional control, a higher toxicity is expected especially with concomitant platinum 100 mg/mq based chemotherapy. A comparison between sequential IMRT (S-IMRT) and SIB- IMRT was planned. The aim was to evaluate the tolerability and safety of SIB regimen in HPV negative patients with locally advanced OPSCC Material and Methods Patients with histologically proven HPV negative OPSCC, staged T3-4 with or without involved lymph nodes at diagnosis, who received primary CRT, were included. S- IMRT was defined as radiotherapy equivalent to 70 Gy (2 Gy/fraction). SIB-IMRT was administered to a total dose of 67.5 Gy (2.25 Gy/fraction) to high dose volume and 60 (2 Gy/fraction) and 54 Gy (1.8 Gy/fraction) to high risk and low risk volumesrespectively.. Fusion CT–MR imaging with a deformable registration software was performed to accurately localize target volumes and organs at risk. Concomitant cisplatin (100mg/m2 on day 1 and day 22 day of treatment) was used. Results A total of 46 patients (31 males, 15 females) with a median age of 64 years (range 41-75) were examined between February 2009 and March 2016. All patients completed the programmed CRT treatment. No patients suspended planned chemotherapy and all patients received the IMRT prescribed total dose. No severe life risking complications occurred and no significant differences between S-IMRT and SIB-IMRT were observed in term of major acute toxicities. Details are shown in table 1