ESTRO 38 Abstract book

S790 ESTRO 38

4 National Centre of Oncological Hadrontherapy CNAO- University of Pavia, Radiation Oncology- Department of Clinical Surgical- Diagnostic and Pediatric Sciences, Pavia, Italy ; 5 National Centre of Oncological Hadrontherapy CNAO- European Institute of Oncology, Radiation Oncology, Pavia- Milano, Italy Purpose or Objective The re-irradiation of locally recurrent rectal cancer presents challenges due to the proximity of critical organs such as bowel. Ion beam therapy, specifically carbon ions radiotherapy (CIRT) have some advantages for the favorable relative biological effectiveness and physical dose distribution providing a highly conformal dose distribution while minimizing normal tissue damage. The aim of this study is to report our experience on feasibility and toxicity of carbon-ion radiotherapy (CIRT) in previously irradiated patients with locally recurrent rectal cancer. Material and Methods Between August 2014 and February 2017, a total of 10 patients (M:F= 8:2) were treated with CIRT as re- irradiation for locally recurrent rectal cancer at National Centre of Oncological Hadrontherapy (CNAO). Patient ages ranged between 46 to 78 years (median 58.5 years). All patients had a history of surgery and pelvic radiotherapy. Specifically, the dose of previous radiotherapy ranged from 45 to 50.4 Gy in 9 patients one of which received a brachytherapy boost up to a total dose of 20Gy. One patient was irradiated with a total dose of 76 Gy for a prostatic cancer. One patient, at time of the first recurrence, underwent to re-irradiation with stereotactic radiotherapy (30 Gy in 6 fractions). They had 7 presacral, 1 perineal, 1 perianal and 1 pre-coccygeal relapses. Three patients received spacer implantation prior to CIRT to secure adequate distance between bowel and tumor. Toxicity was scored according CTCAE 4.0 scale. Results The median interval between the two courses of radiotherapy was 89.3 months (range: 13.8 - 138.2). Median total dose of CIRT was 60 GyRBE (range: 35-76.8) and was administered in a median number of 16 fractions (range: 15-20) over 4 weeks (from 3 to 4.8 Gy RBE/fraction). The GTV ranged from 7.21 to 300.8 cm 3 with a median of 28.42 cm 3 . The PTV ranged from 53.55 to 742.64 cm 3 . All patients completed the scheduled treatment course. Median follow-up was 13 months. Acute toxicity was mild and mainly neuropathic: grade 2 (G2) neuropathic pain in 1 (10%) and G1 in 2 (20%) patients. The major late toxicities were peripheral neuropathy (20%, G2). No G≥3 acute/late reaction nor pelvic infections were observed. Four patients were diagnosed with local progression after carbon ion radiotherapy with a median disease free survival of 11.4 months (range: 2.4- 39.7). Three patients experienced systemic progression. The estimated 1-year-local control rate was 80%. Conclusion In our experience, CIRT for locally recurrent rectal cancer appears to be safe and effective with an acceptable rate of morbidity of normal tissue. More data and longer follow-up are required to investigate the long-term disease control and to determine late effects. EP-1457 Moderate hypofractionation and SIB with volumetric modulated arc therapy (RapidArc) for anal cancer A. Tozzi 1 , C. Iftode 2 , S. Cozzi 2 , G.R. D'Agostino 2 , C. Franzese 2 , L. Di Brina 2 , T. Comito 2 , F. De Rose 2 , I. Renna 2 , D. Franceschini 2 , P. Navarria 2 , E. Clerici 2 , P. Mancosu 2 , F. Lobefalo 2 , A. Stravato 3 , M. Scorsetti 4 1 Humanitas Research Hospital, Radiotherapy and Radiosurgery, Rozzano Milan, Italy ; 2 Humanitas Research Hospital, Radiotherapy and Radiosurgery, Rozzano, Italy ; 3 Humanitas Research Hospital,

Radiothera and Radiosurgery, Rozzano, Italy ; 4 Humanitas Huniversity, Department of Biomedical Sciences, Rozzano, Italy Purpose or Objective This is a retrospective analysis of patients affected by anal squamous cell carcinoma treated with moderatly hypofractionated radiotherapy and concurrent chemotherapy according to the Nigro schedule. End-point of the analysis were the assessment of acute and late toxicity and clinical response Material and Methods Data of Patients affected by locally advanced anal squamous carcinoma and submitted to exclusive chemoradiation were retrospectively analyzed. Radiotherapy was delivered in 28 daily fractions by Linear accelerators with the VMAT technique in its RapidArc form. Before each radiotherapy fraction a cone –beam CT was performed to verify the patient setup (IGRT). Physical examinations and toxicity assessments were performed during and after RT according to CTCAE v4.0. Tumour response was evaluated on CT-MRI-PET scans using the RECIST modified criteria Results From 2016 to 2018, 40 patients were treated in our Institution. Median age of patients was 65 years ; 93% had Stage II-III. Dose ranged from 61.6 to the primary tumor and nodes CT-PET positive to 50.4 Gy to the elective nodes. Thirty-eight (95%) patients were submitted to concomitant chemotherapy; two patients were submitted to radiotherapy only, because unfit for chemotherapy. Acute genitourinary toxicity was reported in the form of grade 1 by 11 patients (27.5%) and grade 2 by 3 patients (7.5%). Acute rectal toxicity was observed in 29 patients (72.5 %) as grade 1 and 4 patients (10%) as grade 2. Acute skin toxicity of grade 3 was diagnosed in 3 patients (7.5%). Acute gastrointestinal toxicity was reported by 31 patients (77.5%) as grade 1, 3 patients (7.5%) as grade 2 and 2 patient (5%) as grade 3. Late toxicity was represented by grade 1 genito-urinary toxicity in 4 patients (10%), and grade 1 and 2 rectal toxicity in 17 and 3 patients( 42.5% and 7.5%), respectively. Late skin toxicity was reported by 8 and 3 patients (20% and 7.5%) as grade 1 and 2, respectively. Late gastrointestinal toxicity was reported by 12 patients (40%) as grade 1 ; no late intestinal toxicity of grades 2 and 3 were recorded. At the restaging workup ,34 patients (85%) achieved a complete response and 6 patients (15%) a partial response. No patient had local progression during follow-up while one patients had metastatic progression of disease. All but one patient were alive at time of analysis Conclusion Moderate hypofractionation with SIB and RapidArc was shown to be safe, with acceptable toxicity. Longer follow- up is needed to assess clinical outcome EP-1458 Acute toxicities comparing VMAT versus 3D- CRT in locally advanced rectal cancer M. Zimmermann 1 , S. Weick 1 , F. Exner 1 , A. Richter 1 , M. Flentje 1 , B. Polat 1 1 University hospital Wuerzburg, Department of radiation oncology, Wuerzburg, Germany Purpose or Objective In locally advanced rectal cancer multimodal treatment including neoadjuvant radio(chemo)therapy is standard of care. The use of modern radiotherapy treatment techniques like IMRT and IGRT are becoming more common. Here, we analysed the impact of VMAT planning on bladder and small bowel sparing in comparison to conventional treatment planning. Material and Methods From 08/2015 to 01/2018, 35 patients with rectal cancer with UICC stage II and III were included in this retrospective analysis. All patients received long-term 5-