ESTRO 2021 Abstract Book

S206

ESTRO 2021

Conclusion In a large population-based database, combined modality therapy with adjuvant EBRT or VBT and chemotherapy appears to improve survival in women with surgically staged FIGO IB grade 3 endometrioid adenocarcinomas and papillary serous/clear cell uterine carcinomas in comparison to adjuvant EBRT alone. OC-0300 Patients’ and clinicians’ preferences in adjuvant treatment for high-risk endometrial cancer C. Post 1 , J.W. Mens 2 , M. Haverkort 3 , F. Koppe 4 , I. Jürgenliemk-Schulz 5 , A. Snyers 6 , E. Roeloffzen 7 , E. Schaake 8 , A. Slot 9 , T. Stam 10 , J. Beukema 11 , H. van den Berg 12 , L. Lutgens 13 , H. Nijman 14 , C. de Kroon 15 , J. Kroep 16 , A. Stiggelbout 17 , C. Creutzberg 18 1 Leiden University Medical Center, Radiation Oncology, Leiden, The Netherlands; 2 Erasmus MC, Radiation oncology, Rotterdam, The Netherlands; 3 Radiotherapiegroep, Radiation oncology, Arnhem, The Netherlands; 4 Institute Verbeeten, Radiation oncology, Tilburg, The Netherlands; 5 University Medical Center Utrecht, Radiation oncology, Utrecht, The Netherlands; 6 Radboud University Medical Center, Radiation oncology, Nijmegen, The Netherlands; 7 Isala, Radiation oncology, Zwolle, The Netherlands; 8 National Cancer Institute, Radiation oncology, Amsterdam, The Netherlands; 9 Radiotherapeutic Institute Friesland, Radiation oncology, Leeuwarden, The Netherlands; 10 Haaglanden Medical Center, Radiation oncology, Den Haag, The Netherlands; 11 University Medical Center Groningen, Radiation oncology, Groningen, The Netherlands; 12 Catharina Hospital, Radiation oncology, Eindhoven, The Netherlands; 13 Maastro, Radiation oncology, Maastricht, The Netherlands; 14 University Medical Center Groningen, Obstetrics and gynaecology, Groningen, The Netherlands; 15 Leiden University Medical Center, Obstetrics and gynaecology, Leiden, The Netherlands; 16 Leiden University Medical Center, Medical oncology, Leiden, The Netherlands; 17 Leiden University Medical Center, Biomedical data sciences, Leiden University Medical Center, The Netherlands; 18 Leiden University Medical Center, Radiation oncology, Leiden, The Netherlands Purpose or Objective Decision making regarding adjuvant therapy for high-risk endometrial cancer is complex. The aim of this study was to determine patients’ and clinicians’ minimally desired survival benefit to prefer adjuvant chemoradiotherapy over pelvic radiotherapy alone. Moreover, influencing factors and relative importance of clinical benefits and side effects were investigated. Materials and Methods Patients with high-risk endometrial cancer treated with pelvic radiotherapy between 2014 and 2020 were enrolled in 12 radiation oncology centres across the Netherlands. These patients and multidisciplinary gynaecologic oncology clinicians were asked to complete a self-administered trade-off questionnaire. An overview with the most frequent short- and long-terms symptoms and influences on functioning was presented, based on data from the quality of life analysis of the PORTEC-3 trial. The survival benefit was varied systematically to identify the minimally desired benefit from chemotherapy. The importance assigned to every benefit or side effect was rated using a 4-point Likert-type response scale. Continuous and ordinal variables were compared using Mann-Whitney U test. Multivariable logistic regression with likelihood-based backward selection was performed to identify predictors for chemoradiotherapy preference at a 5-year survival benefit of 5%. Results In total, 171 patients and 63 clinicians completed the questionnaire. Median age of patients was 67 [IQR 60-72] years and 42 (24.6%) of patients had received chemoradiotherapy. Median minimally desired benefit to make chemoradiotherapy worthwhile was higher for patients versus clinicians (10% [IQR 4-20%] vs 5% [IQR 3-10%] survival benefit at 5-years, p =0.02). Figure 1 shows that both patients and clinicians rated survival benefit as most important during decision making, followed by long-term symptoms (i.e. the chance of persisting peripheral neuropathy and decline in physical functioning). Older patients (OR 0.92 [95%CI 0.87-0.97], p =0.003) with comorbidity (OR 0.34 [95% CI 0.12-0.89], p =0.035) had lower preference for chemoradiotherapy,