Challenging the Binary Classification of Endometrioid Endometrial Adenocarcinoma: The Evaluation of Grade 2 as an...

Background: Although grade is a well-recognised prognostic factor for endometrioid endometrial cancer (EEC), in more studies grade 1 (G1) and grade 2 (G2) EEC are combined and compared together with grade 3 (G3) tumours. The aim of our study is to separately investigate the outcomes, prognostic factors and recurrence patterns of G2 EEC and whether the differentiation between G1 and G2 EEC is clinically useful. Methods: we retrospectively reviewed 523 patients with EEC treated with primary surgery over a decade (March 2010-January 2020) at Oxford University Hospitals NHS Trust, focusing on those with G2 disease. Results: Patients with G2 EEC had worse 5-year cancer-specific survival (93.3% vs. 98.5%, p < 0.01) compared to patients with G1 EEC, but a favourable prognosis compared to G3 EEG, both in terms of disease-free survival (91.6 vs. 83.8%, p = 0.04) and cancer-specific survival (93.3% vs. 78.5%, p < 0.01). Both stage and grade are independent risk factors for cancer-specific mortality in EEC. Cervical stromal involvement, parametrial involvement and distant metastatic disease are all independent risk factors for cancer-related mortality in G2 ECC. Only 12.5% of recurrences of G2 EEC were diagnosed with examination in routine follow up in asymptomatic patients. Conclusions: our results suggest that the grading system should continue to differentiate G1 EEC and G2 EEC for better prognosis interpretation.