ESTRO 36 Abstract Book

S688 ESTRO 36 _______________________________________________________________________________________________

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 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.

Results Thirty-nine pts treated from May 2015 to February 2016 were included in this analysis. The median age was 64 years [range 44-77years]; Male-Female ratio was 2.2. Clinical involvement of mesorectal fascia was detected in 18 pts (46%). CTV2 included always presacral space and internal iliac nodes, in 30 pts (77%) and in 4 pts (10%) the obturator nodes and the external iliac nodes were added, respectively. 5 pts received CT in the pre-surgical pause. 38 pts received a Total Mesorectal Excision surgery (69% Anterior Resection and 26% Abdominal-Perineal Resection), in 2 pts (5%) a WW approach was preferred. Adjuvant CT was administered to 18 pts. The radiation prescribed dose was entirely delivered in all pts. GI toxicity was recorded in 31 pts (79%): diarrhea and proctitis were most detected. Four cases of grade 3 GI toxicities were registered (6% of all GI toxicities). GU and HE toxicities were less frequent: non infective cystitis (13 pts) and neutropenia (6 pts) were observed. However, none of them presented a toxicity grade≥ 3. About CT, 8 pts (20%) received less than 4 cycles of concomitant CT because of HE or GI toxicity. pCR was achieved in 10 pts (26%). TRG grade 1 2 3 and 4 was recorded in 11 (28%), 8 (20.5%), 13 (33%) and 5 (13%), respectively. At the median follow-up of 18 weeks the local control, the disease-free survival and the overall survival rates were 100%, 92% and 97%, respectively.