ESTRO 2021 Abstract Book

S96

ESTRO 2021

SP-0154 Pathology aspects X. Matias-Guiu 1 1 Hospital U de Bellvitge, Pathology, Barcelona, Spain

Abstract Text Pathology is an important part of the ESGO-ESTRO-ESP Guidelines in endometrial cancer. Several recommendations are performed in different areas: 1- Identification and surveillance of women with a pathogenic germline variant in a lynch syndrome- associated gene •To identify patients with Lynch syndrome and triage for germline mutational analysis, MMR IHC (plus analysis of MLH1 promotor methylation status in case of immunohistochemical loss of MLH1/PMS2 expression) or MSI tests should be performed in all endometrial carcinomas, irrespective of histologic subtype of the tumour. 2- Molecular markers for endometrial carcinoma diagnosis and as determinants for treatment decisions •Molecular classification is encouraged in all endometrial carcinomas, especially high-grade tumours . •POLE mutation analysis may be omitted in low-risk and intermediate risk endometrial carcinoma with low grade histology. 3- Definition of prognostic risk groups integrating molecular markers •Histopathological type, grade, myometrial invasion and LVSI (no/focal/substantial) should be recorded in all patients with endometrial carcinoma. •The definition of prognostic risk groups is presented when Molecular Classification is known or unknown. 4- Pre- and intra-operative work-up •Histopathological tumour type and grade in endometrial biopsy is required. •Intra-operative frozen section is not encouraged for myometrial invasion assessment because of poor reproducibility and interference with adequate pathological processing . Conclusion: Integration of Conventional pathology and molecular classification is helpful in risk stratification of Endometrial Carcinoma

SP-0155 Surgical aspects N. Concin Austria

Abstract not available

SP-0156 Early stage disease, adjuvant treatment including molecular risk classification C. Creutzberg The Netherlands

Abstract not available

SP-0157 Advanced/relapsed disease A. Taylor 1 1 Royal Marsden Hospital, Gynaecology, London, United Kingdom

Abstract Text The ESGO-ESTRO-ESO guidelines for management of advanced and recurrent endometrial cancer will be discussed.

Poster highlights: Poster Highlights 5: Advanced radiotherapy service implementation

PH-0159 Starting a new era in radiotherapy, transition of work from radiation-oncologist to RTT. L. ten Asbroek 1 , L. Zwart 1 , E. van Dieren 1 , F. Ong 1 , E. de Wit 1 1 Medisch Spectrum Twente, Radiotherapy, Enschede, The Netherlands Purpose or Objective CBCT-guided online adaptive radiotherapy has been introduced as a standard treatment for all our prostate cancer patients and is supervised by either a radiation-oncologist (first four fractions) or an advanced adapter. To this end, a group of RTT’s was trained to contour male pelvic organs on planning-CTs. The objective of the study was to evaluate our training methodology by analysing differences in contours defined by the advanced adapter compared to the approved contours by the radiation-oncologist. Materials and Methods In this retrospective study, planning CTs of thirty prostate cancer patients were included. All approved contours relevant for adaptive radiotherapy (prostate, seminal vesicles, rectum and bladder) were transferred to Eclipse (Varian Medical Systems, Palo Alto, CA) and subsequently masked. Six advanced adapters re- contoured these organs. Resulting contours were compared with the approved contours. In addition, Dice similarity coefficient (DSC), volume changes and Center of Mass (CoM) were calculated with respect to the approved contours. Results The DSC was 0.96 ± 0.01 (bladder), 0.87 ± 0.06 (rectum), 0.83 ± 0.06 (prostate) and 0.73 ± 0.10 (seminal vesicles). For rectum, the main difference was seen in the most cranial and caudal part of the rectum. When only the part of the rectum adjacent to the PTV was measured, the DSC improved (0.92 ±0.03) and the