Unique prognostic features of grade 3 endometrioid endometrial carcinoma: Findings from 101 consecutive cases at a Japanese tertiary cancer center.

Abstract Objective The prognosis of and optimal treatment for grade 3 endometrioid endometrial carcinoma (G3EEC) currently remain unclear. This study aimed to clarify the baseline recurrence risk in patients with early-stage (stage I–II) G3EEC without adjuvant therapy and the prognosis of patients with advanced-stage (stage III–IV) G3EEC. Materials and methods A total of 101 patients with pathologically confirmed G3EEC from 1997 to 2018 were identified. Their clinicopathological characteristics and survival outcomes were reviewed retrospectively. Disease-free survival and overall survival values were estimated according to the Kaplan–Meier method and compared using a log-rank test. Results Recurrence was observed in eight (13%) of 63 patients with early-stage G3EEC, none of whom had received adjuvant therapy. The 5-year disease-free survival and 5-year overall survival rates for these patients were 86.7% and 96.4%, respectively. Recurrence was also observed in 12 (41%) of 29 patients with stage III G3EEC. The 5-year overall survival rates for stage III patients who underwent adjuvant chemotherapy and adjuvant radiotherapy were 85.6% and 42.9%, respectively. The 3-year overall survival rate among stage IVB patients was only 12.7% despite multidisciplinary treatment provision. Conclusion Our study newly demonstrates that patients with early-stage G3EEC have a favorable prognosis and a low recurrence rate in the absence of adjuvant therapy. In patients with stage III G3EEC, adjuvant chemotherapy was more beneficial than adjuvant radiotherapy. The poor prognosis of patients with stage IV G3EEC indicates the need for more effective treatments. Unique therapeutic approaches based on staging are recommended for treatment of G3EEC.