ESTRO 36 Abstract Book

S681 ESTRO 36 2017 _______________________________________________________________________________________________

p =0,72).

complete response rate, with 5 patients having an incomplete response, 4 of whom underwent salvage surgery. At the time of analysis, 5 patients had isolated local relapse following CR at 3 months. Of those, 3 went on to salvage surgery. 7 patients (8%) had distant disease of which 3 patients had both local and distant disease. 2 year colostomy free survival was 75.2%. 12 of the patients had pre-treatment stoma with 7 more patients requiring a colostomy after radiotherapy. Conclusion The outcomes in our series suggest that the excellent outcomes achieved with 3D conformal radiotherapy in ACT2 are reproducible with IMRT, delivered according to UK guidance. A larger multicentre audit of outcomes is planned to confirm our findings. EP-1281 Feasibility and Toxicity analysis of dose- escalation by SIB/VMAT schedule in rectal cancer patients A. Re 1 , G. Chiloiro 1 , M.A. Gambacorta 1 , F. Cellini 1 , A. Pesce 1 , D. Marchesano 1 , G.C. Mattiucci 1 , S. Manfrida 1 , V. Valentini 1 1 Università Cattolica del Sacro Cuore, Radiation Oncology Department, Rome, Italy Purpose or Objective Evaluation of the feasibility of an intensification of radiation dose by simultaneous integrated boost/Volumetric Modulated Arc Therapy (SIB/VMAT) technique in patients (pts) affected by Locally Advanced Rectal Cancer (LARC) based on toxicity profile. Material and Methods Pts affected by non-metastatic LARC underwent neoadjuvant chemo-radiotherapy (CRT). The CRT was delivered in 25 fractions with SIB-VMAT strategy on two volumes: Clinical target volume (CTV)2 received a total dose of 45 Gy/1.8 Gy/fraction on the total mesorectum and the nodes of drainage; CTV1 received 55 Gy/2.2Gy/fraction as a moderate hypofractionated schedule on the tumor and the corresponding mesorectum. Surgery was planned at least 8 weeks after the end of CRT. A watch and wait (WW) strategy was considered if restaging exams showed no detectable disease. Adjuvant chemotherapy (CT) was considered according to risk factors. Acute Gastrointestinal (GI), genitourinary (GU) and hematological (HE) adverse events were recorded according to CTCAE scale v4.0. Collaterally CRT efficacy in terms of pathological Complete response (pCR) was analyzed and Tumor Regression Grade (TRG) on the basis of Mandard scale was recorded.

Conclusion Pathologic response after neoadjuvant therapy for locally advanced rectal cancer is associated with better prognostic results. No correlation between immediate or delayed surgery and tumor regression was observed in this study, suggesting that tumor response depends on other factors besides surgical timing. Further studies should be carried out in order to clearly define predictive factors of tumour response. EP-1280 Clinical outcomes of anal squamous cell carcinoma, treated with IMRT, using UK guidance. S. Sengupta 1 , S. Padmanaban 2 , C. Jacobs 2 , R. Muirhead 3 1 School of Medicine, University of Oxford, Oxford, United Kingdom 2 Oxford Cancer Centre, Oxford University Hospitals, Oxford, United Kingdom 3 CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom Purpose or Objective The largest phase III trial of radical chemoradiotherapy in anal cancer to date, the ACT2 study, used a unique radiotherapy dose, fractionation and target volume to other studies and series; delivering treatment using 3D conformal radiotherapy and setting the standard for treatment delivery in the UK. Following the development of intensity modulated radiotherapy (IMRT) UK guidance was produced adapting ACT2 doses and volumes for IMRT delivery. The acute toxicity of delivery using this guidance has been published, confirming reduced toxicity with IMRT; but there is no large series looking at outcome, to confirm maintained outcomes with this new technique. We report a single series centre assessing patient outcomes when utilizing IMRT as per UK guidance. Material and Methods Between April 2013 and July 2016, 87 patients with anal carcinoma were treated with IMRT in the Oxford University Hospital NHS Trust. We retrospectively reviewed clinical notes for patients and tumour demographics, rates of recurrence and colostomy status. Data was collected and analysed using Microsoft Excel, Microsoft Office Professional Plus 2013 and IBM SPSS Software Version 23. Results The median range of the patient population in this study was 61 (range 37-90), with 29:71 male:female ratio. Rates of Tx/T1/T2 and T3/T4 were 62.1% and 37.9% respectively, node negative (N0) and node positive (N+) were 48.8% and 51.2% respectively. 96.6% of patients were free of metastatic disease prior to radiotherapy. The median follow up time after radiotherapy was 15 months (range 3 to 38 months). The 2 year disease free and overall survival was 76.5% and 83.9% respectively. 94% of patients had a 3 month

Results