554 Where does the prognosis of grade 2 endometrioid endometrial cancer stands in the spectrum between low and high grade endometrioid tumours?

Introduction/Background Although grade is a well-recognised prognostic factor for endometrioid endometrial cancer, in more studies grade I (G1EEC) and grade II (G2EEC) endometrioid endometrial carcinomas are combined and compared together with grade III (G3EEC) tumours. The aim of our study is to investigate separately the outcomes of grade II endometrioid endometrial adenocarcinomas and investigate whether the differentiation between G1EEC and G2EEC is clinically useful. Methodology We retrospectively reviewed the files of patients treated with primary staging surgery for endometrioid endometrial cancer in Churchill Cancer Centre – Oxford University Hospitals NHS Foundation trust between 2010 and 2020. Results Out of the 523 patients endometrioid endometrial cancer treated with primary surgery, 189 (36.14%) were G2EEC. Patients with G2EEC had comparable 5-years disease-free survival rates (91.6% vs. 93.2%, p=0.44), but worse 5-year cancer specific survival (93.3% vs. 98.5%, pConclusion Although grade does not seem to affect recurrence of endometrioid endometrial cancer independently, cancer specific survival of G2ECC is significantly different from both G1EEC and G3ECC. Therefore, grading system should continue to differentiate G1EEC and G2EEC for better prognosis interpretation. Disclosures Nothing to disclose.