Impact of adjuvant treatment on survival in patients with 2023 FIGO stage IIC endometrial cancer: a retrospective analysis from two tertiary centers in Korea and Taiwan

Objective: In early-stage endometrial cancer, aggressive histologic types (grade 3 endometrioid, serous, clear cell, carcinosarcomas, undifferentiated, mixed, and other unusual types) are associated with an increased risk of distant metastases and worse survival. However, the optimal adjuvant treatment for these patients remains controversial. The present study investigated the outcomes of different adjuvant treatments in patients with 2023 FIGO stage IIC endometrial cancer. Methods: We retrospectively identified patients with 2023 FIGO stage IIC endometrial cancer who underwent surgery followed by either adjuvant treatment or observation from 2000 to 2020 at two tertiary centers in Korea and Taiwan. Recurrence-free survival (RFS) and overall survival (OS) were evaluated using Kaplan-Meier estimates and Cox proportional-hazards models. We also analyzed recurrence patterns after different adjuvant treatments. Results: A total of 272 patients were identified; 204 received adjuvant treatment postoperatively, whereas 68 only underwent observation. Adjuvant treatment was not associated with improved RFS or OS. Non-endometrioid histologic types (p=0.003) and presence of lymphovascular space invasion (LVSI, p=0.002) were associated with worse RFS, whereas only non-endometrioid histologic types impacted OS (p=0.004). In subgroup analyses, adjuvant treatment improved OS in patients with LVSI (p=0.020) and in patients with both LVSI and grade 3 endometrioid histologic type (p=0.007). We found no difference in locoregional and distant recurrence between patients undergoing adjuvant treatment or observation. Conclusion: In this study, the addition of adjuvant treatment was associated with an OS benefit for patients with LVSI, especially those with grade 3 endometrioid tumors.