Impact of para-aortic lymphadenectomy on clinically FIGO stage IIIC1 high- grade endometrial cancer: a retrospective cohort study from two tertiary centers Running title: Lymphadenectomy in high-grade endometrial cancer

The therapeutic effect of para-aortic lymphadenectomy in patients with clinically pelvic node-positive but para-aortic node-negative endometrial cancer remains controversial. In this study, we investigated whether combined pelvic and para-aortic lymphadenectomy has a survival benefit compared with pelvic lymphadenectomy alone in these patients. We retrospectively reviewed patients with clinically FIGO stage IIIC1 high-grade endometrial cancer at two tertiary centers. Patients were stratified according to type of lymphadenectomy and subgroup analyses were performed. Kaplan–Meier analysis and a Cox proportional-hazards model were used to evaluate survival outcomes. A total of 56 patients were identified. Of these patients, 18 underwent pelvic lymphadenectomy alone, and 38 underwent combined pelvic and para-aortic lymphadenectomy. After staging surgery, 34 (60.7%) patients had pathologically confirmed lymph node metastases. Within a median follow-up of 57.5 months, there were no significant differences in recurrence-free survival (RFS) and overall survival (OS) between the two groups. In subgroup analyses, the node- and lymphovascular space invasion (LVSI)-positive patients characterized by grade 3 endometrioid histologic type (p = 0.010) or negative peritoneal washing cytology (p = 0.035) had an RFS benefit from combined pelvic and para-aortic lymphadenectomy.