ESTRO 2020 Abstract book

S399 ESTRO 2020

Conclusion MRI was useful and feasible to identify and contour emerging female pelvic floor structures. This atlas could be employed for evaluation of OARs’ sparing in the era of high-conformal RT. PD-0657 Survival in optimally resected stage III endometrial cancer: adjuvant radiotherapy in the modern era J.L. CHEN 1 , C. Pan 2 , Y. Liou 3 , C. Kuo 4 , Y. Huang 5 1 National Taiwan University Hospital and National Taiwan University College of Medicine, Oncology, Taipei, Taiwan ; 2 National Taiwan University Hospital and National Taiwan University College of Medicine, Medical Research, Taipei, Taiwan ; 3 National Taiwan University Hospital, Laboratory Medicine, Taipei, Taiwan ; 4 National Taiwan University Hospital and National Taiwan University College of Medicine, Clinical Laboratory Sciences and Medical Biotechnology, Taipei, Taiwan ; 5 National Taiwan University Hospital and National Taiwan University College of Medicine, Radiology, Taipei, Taiwan Purpose or Objective Adjuvant treatment for stage III endometrial cancer is still undefined. This study investigates how tumor characteristics and adjuvant treatments (adjuvant chemotherapy, radiotherapy, or both) can influence survival in women with optimally resected stage III endometrial cancer in this era of modern radiotherapy. Material and Methods This multi-institutional study retrospectively reviewed patients with surgically staged endometrial cancer who were treated between 2010 and 2018. In those women who received adjuvant radiotherapy, it was performed using intensity-modulated radiotherapy, with or without vaginal brachytherapy. The study cohort was evaluated using Kaplan–Meier estimates of recurrence-free survival (RFS) and overall survival (OS) and proportional hazard modeling. Results In total, 161 patients were considered for this study (52 stage IIIA, 9 stage IIIB, and 100 stage IIIC patients). Of these, 154 patients (96%) received an adjuvant treatment—chemotherapy (67; 42%), radiotherapy (29; 18%), or combined chemo-radiotherapy (58; 36%). The 5- year RFS and OS were 61% and 80% for patients treated with adjuvant chemotherapy, 75% and 86% with adjuvant radiotherapy, and 69% and 89% with both adjuvant radiotherapy and chemotherapy, respectively. In the stage IIIC cohort, patients who received adjuvant radiotherapy, with or without chemotherapy, (n = 59) had an improved 5-year RFS (74% vs 54%, p = 0.045) and OS (92% vs 72%, p = 0.020) than those who received only adjuvant chemotherapy (n = 37). Adjuvant radiotherapy, with or without chemotherapy, was associated with an improved RFS for patients with an endometrioid histology (p = 0.048), with >2 positive lymph nodes (p = 0.014), and aged >60 years (p = 0.022). Conclusion In this era of intensity-modulated radiotherapy, the use of adjuvant radiotherapy, with or without chemotherapy, was associated with improved survival in women with optimally resected stage III endometrial cancer. In particular, it may be beneficial for patients with an endometrioid histology, with >2 positive lymph nodes, and aged >60 years. These findings should be further investigated in prospective clinical trials.