ESTRO 2020 Abstract book

S622 ESTRO 2020

additional simultaneous integrated boost (SIB) up to 50, 52 or 54Gy to either primary tumour, pelvic lymph nodes (LN) or both has been developed. The purpose of this retrospective audit was to investigate the toxicity of treatment and patient outcomes of this new technique. Material and Methods All patients treated with rectal VMAT and SIB between 2015-18 were identified. Data was collected on patient characteristics, acute toxicity (within 3 months of completion of CRT), long-term toxicity (greater than 3 months after completion of CRT), radiotherapy parameters (such as the boost planning target volume (PTV boost ) and dose to organs at risk (OARs)), and response parameters (clinical, pathological and radiological). Results A total of 66 patients, 49 men and 17 women, were identified (median age of 66 years). Fifty two percent of tumours were located in the lower third of the rectum, 24% mid and 21% upper. The SIB was given to pelvic LN regions in 50% of patients, to primary site in 44%, and to

Conclusion Weak supervised deep learning method have potential to predict CMS on WSIs. This model can predict CMS on WSIs directly and avoid gene sequencing which may make it possible for CMS becoming an accessible reference for colorectal cancer’s therapy. PO-1086 Innovative technologies in treatment of patients with squamous cancer of the anal canal V. Glebovskaya 1 , T. Sergey 1 , A. Nazarenko 1 , P. Bulychkin 1 1 National Medical Research Center of Oncology named by N.N. Blokhin, Radiation Oncology Department, Moscow, Russian Federation Purpose or Objective The increase in number of cured patients with squamous cell anal carcinoma and the quality of life is directly related to improvement of radiotherapy departments’ technical equipment in oncological clinics. Most precise determination of tumor volume using modern diagnostic methods, which give a possibility to make maximum impact on the tumor and identified affected lymph nodes while limiting dose to organs at risk, and also reduction of chemoradiotherapy course duration are ones of the main goals of radiotherapy technologies’ improvement. Material and Methods During the period from 2000 to 2015, 301 patients with squamous cell anal carcinoma, stage T1-4N0-3M0-1, were treated by radiation therapy with 2DRT, 3DCRT, or IMRT in a total dose of 50-60 Gy in combination with chemotherapy. Results The use of IMRT with MRI in comparison with 3DCRT resulted in an increase of frequency of complete tumor response (at the time of first diagnostic control) up to 67.5% (p = 0.071); reduction of frequency of interruptions in the treatment course up to 48% (p = 0.005); significantly increased the 3-year overall survival rate to 92.9% (p = 0.05), distant metastases-free survival - 91% (p = 0.049), with a trend of improvement in locoregional control - 89.9% (p = 0.179). Conclusion The use of radiation therapy in its modern version has reduced the rate of interruptions in the treatment course, has achieved high immediate and long-term oncological results, has reduced the frequency and severity of early and late chemoradiation complications. PO-1087 Simultaneous integrated boost and volumetric modulated arc radiotherapy in rectal cancer B. Low 1 , J. Saunders 1 , A. Othman 1 , P. McLoone 2 , N. Mohammed 1 , L. Ranford 1 , K. Smith 1 , W. Campbell 1 , B. Hunter 1 , G. Marshall 1 1 Beatson West of Scotland Cancer Centre, Clinical oncology, Glasgow, United Kingdom ; 2 University of Glasgow, Institute of Health and Wellbeing, Glasgow, United Kingdom Purpose or Objective Technological advances in radiotherapy technique have allowed dose escalation in many tumour types. There is better local tumour control with increased radiation dose. In this centre, rectal radiotherapy treatment using volumetric modulated arc radiotherapy (VMAT) with an

both regions in 6%. The median PTV boost

treated with SIB was 154cc (IQR 41 to

was larger (266cc

265). The primary tumour PTV boost IQR(178-367), than the pelvic LN PTV boost

(44cc (IQR 22-

103). Patients who received SIB to pelvic LN regions were more likely to receive 54Gy (73%, n=24) compared to SIB to the primary with 62% (n=18) receiving 52Gy ( figure 1 ).

Figure 1. Number of patients assigned a 50Gy, 52Gy or 54Gy SIB, boost location and dose constraint of two OARs. All patients completed CRT except one patient who discontinued at fraction 22 due to grade 3 diarrhoea. The most commonly reported acute toxicities were skin reactions (29%) and proctitis (24%). The most commonly reported long-term toxicities were fatigue (8%) and small/large intestine problems (6%). There was an association between size of PTV boost and acute toxicity; 36% of patients with PTV boost <100cc experienced acute toxicity compared to 71% with volume of >200cc (OR 4.4 95%CI (1.3 to 15.5), p=0.019). After adjusting for sex and level of cancer the odds ratio reduced to 3.1 (0.8 to 11.9), p=0.1 ( table 1 ).

Table 1. Comparison of % acute toxicity with PTV boost volume * * 4 patients were excluded due to data error Conclusion Rectal VMAT with SIB is a relatively new technique. Our results demonstrate an association with PTV boost volume and acute toxicity but no association with PTV boost dose was found in this study.