ESTRO 38 Abstract book

S801 ESTRO 38

radiotherapy has been performed using a small pelvic field technique without brachytherapy since 2007. This report aims to analyze the results of those patients in terms of locoregional control, overall survival and acute toxicity. Material and Methods For this retrospective analysis, all patients treated at the Radiation Oncology Unit of our hospital between 2007 and 2014 were included. Adjuvant radiotherapy without concurrent chemotherapy was administered to FIGO IB1 cervical cancer patients with a combination of ≥2 of the following intermediate risk factors: lymph-vascular space invasion, deep stromal invasion and/or increased tumor size on pathology. Patients were treated with 3D- conformal radiotherapy, using a small pelvic 4-field box technique, with the upper limit at the inferior border of the sacroiliac joint. Acute genitourinary and gastrointestinal toxicities were classified according to the RTOG grading (G) system. Overall survival and relapse- free survival were analyzed using the Kaplan-Meier method. Results 20 patients treated with small pelvic field radiotherapy were identified. Median follow-up time for the whole group was 37.5 months (IQR 20 – 66.5). Median age was 46 years (IQR 36.5 – 56). Nineteen patients underwent radical hysterectomy and 1 patient underwent radical trachelectomy. Median number of resected lymph nodes was 21.5 (IQR 18-28.5). Reported histologic types were squamous-cell carcinoma (15 patients), adenocarcinoma (2 patients), adenosquamous (2 patients), and clear cell carcinoma (1 patient). Median tumor size was 3 cm (IQR 2.3-3.5). Stromal invasion was 2/3 in 12 patients and 3/3 in 7 patients, and lymph-vascular space invasion was present in 16 patients. The prescribed dose was 50.4 Gy in 19 patients and 45 Gy in one patient. Acute genitourinary toxicity was G0 in 12, G1 in 6, G2 in 1 and G3/4 in 0 patients. Acute gastrointestinal toxicity was G0 in 10, G1 in 4, G2 in 6 and G3/4 in 0 patients. Three-year relapse-free survival was 84.6%. 3 patients presented relapses; 1 classified as local relapse, 1 located in the retrovesical area, and 1 located lateral to L5 vertebra. Three-year overall survival was 100%. Conclusion Adjuvant small pelvic field radiotherapy is associated with good oncological outcomes and an excellent toxicity profile in patients with FIGO IB1 cervical cancer with intermediate risk factors. Only one patient experienced a relapse in a region that would have been treated with a standard pelvic field. EP-1479 The use of CT texture analysis in cervical cancer to predict response to chemoradiotherapy S. Otter 1 , A. Franklin 1 , P. Evans 2 , A. Stewart 1 1 Royal Surrey County Hospital, St Luke's Cancer Centre, Guildford, United Kingdom ; 2 University of Surrey, Centre for Vision- Speech and Signal Processing, Guildford, United Kingdom Purpose or Objective Cervical cancer is the fourth most common cancer worldwide and the 5-year overall survival for stage IIIB disease is only 42%. Treatment for locally advanced cervical cancer (LACC) is chemoradiotherapy (CRT). It would be beneficial to identify at an early stage, patients who may not have a complete response to treatment so that they could have dose escalation or the addition of other systemic agents to improve the chance of cure. Texture analysis (TA) enables the quantification of the spatial heterogeneity of tumours thereby giving more information about a tumour than is available from visual analysis alone. The aim of this study was to apply TA to pre-treatment and brachytherapy CT scans of patients with LACC who were then treated with CRT.

EP-1477 Image-guided Intensity Modulated Radiotherapy in cervical cancer: organ motion and geograpical miss P. Ferrazza 1 , A. Delana 2 , L. Purpura 3 , E. Magri 1 , L. Bandera 1 , V. Vanoni 1 1 Ospedale Santa Chiara di Trento, Radiation Oncology, Trento, Italy ; 2 Ospedale Santa Chiara di Trento, Medical Physics, Trento, Italy ; 3 Università degli Studi di Palermo, Radiation Oncology, Palermo, Italy Purpose or Objective Volumetric Modulated Radiotherapy (VMAT) is increasingly used in order to minimize toxicity in cervical cancer. However, to prevent geographical misses caused by inter-fraction movement of uterus, the benefit of this approach is detracted by margins applied to Clinical Target Volume (CTV) to obtain Planning Target Volume (PTV). The aim of this retrospective analysis is to verify how variations in bladder filling may cause target miss and unnecessary organs at risck inclusion in high dose regions. Material and Methods From March 2016 to January 2018 10 patients (pts) with cervical cancer stage FIGO IIB underwento to concurrent radio-chemotherapy (total dose 45-50.4 Gy/25-28 fractions), followed by intrauterine high-dose brachytherapy. Full and empty bladder Computed Tomography (CT) scans were acquired prior the treatment to evaluate uterus, rectal and bowel motion. A VMAT plan based of the CT with full bladder was performed (by Montecarlo algorithm), after image fusion and delination of the uterus in both CT scans (to create the uterus Internal Target Volume ITV). We applied isotropic margins of 7 and 10 mm respectively to lymph node-cervix and uterus ITV. Daily Cone Beam CT (CBCT) was performed. We analysed 113 of 273 CBCT, due to the presence of artefacts in images. CBCTs were registrated to CT simulation and an operator contoured bladder and uterus on each CBCT. Results The main cause of uterus motions in our analysis was bladder filling. The uterus shifts are wider in aterior- posterior and superio-inferior directions with larger movemets of the fundus and lesser along the endocervical canal. Rectum filling or bowel interposition did not result in uterus motion outside the PTV 88% of CBCTs showed that uterus was included in PTV, expecially in pts with correct bladder filling in simulation CT. A further analysis showed that an increase in superior- inferior and antero-posterior margins (anisotropic margins, 1.5 cm vs 1 cm) from uterus ITV, reduces by 9% the risk of target miss (from 12 to 3%). Dose constrains of bowel were respected despite the increase of PTV. Conclusion Pelvic organ motion is patient specific, and a correct bladder filling in CT simulation seems to reduce geographical misses during radiation treatment. The large CTV-PTV margins can increase gastrointestinal, genitourinary and hematological toxicity, but anisotropic margins in our preliminar analysis improve PTV coverage (respecting dose constraints of bowel and rectum). Due to the small sample size, Further validation of these results is necessary. EP-1478 Adjuvant small pelvic field radiotherapy in cervical cancer with intermediate risk factors J.A. Solis Campos 1 , B. Tudela Staub 1 , G. Veillon Contreras 1 , I. Perrot rosenberg 2 1 Hospital Carlos Van Buren, oncology, Valparaíso, Chile ; 2 Universidad de Valparaiso, School of Medicine, Valparaíso, Chile Purpose or Objective Adjuvant radiotherapy improves outcomes in surgically treated cervical cancer patients with intermediate risk factors as defined by Sedlis. In our hospital, adjuvant