ESTRO 36 Abstract Book

S591 ESTRO 36 _______________________________________________________________________________________________

a decrease in the cellularity in the tumour & tumour response. Thus, a rising ADC value during treatment versus Pretreatment ADC values may be used to predict outcomes. The aim of this study was to investigate the role of diffusion weighted MRI derived parameters like ADC, as an imaging biomarker, to predict response to RT in locally advanced squamous cell carcinoma of the larynx and hypopharynx. Material and Methods From May 2014 to August 2015, 19 patients with locally advanced laryngeal & hypopharyngeal malignancies, treated with organ preservation intent with concurrent radiotherapy with Cisplatin (n=14), radiotherapy with Nimotuzumab (n=2) and radical radiotherapy (n=3) were recruited. The patients were all male with predominantly T3 stage. They were assessed for treatment response with dWMRI at baseline, first week, fourth week during RT and at the time of first response assessment at 6 to 8 weeks after RT. The ADC values were compared at different time points and correlated with the treatment response. Results All the 19 patients in the study showed an increasing trend in the ADC values over the chosen 4 different time points. It was observed that an abrupt rise from the pretreatment ADC to the first week ADC was characteristic of complete response while a gradual rise of ADC over the different points suggested a partial treatment response. The patients who responded to chemoradiation therapy had a higher pretreatment ADC than patients with partial response. At the last follow up, 12 patients were disease free, while 5 patients developed recurrence. Four patients with recurrence had shown a partial response while only one had exhibited a complete response during RT. One patient died during treatment of aspiration pneumonia while undergoing CRT & another did not follow up after completion of treatment. Conclusion This study suggests that an abrupt rise in the ADC value in the tumour after one week of treatment may predict complete response & long term tumour control. However this finding needs to be investigated in a larger cohort of 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 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,