Objective The aim of this study was to investigate the association of predictors of an advanced disease and/or poor outcome with the occurrence of tumor relapses in different anatomical sites in patients with stage I–II endometrioid endometrial cancer.

Methods A total of 929 patients were included in the study. The median follow-up time was 57 months (range, 1–108 months). The studied variables were: poor tumor differentiation, myometrial invasion 50% or greater, tumor size 3 cm or greater, lymphovascular space invasion, cervical stromal invasion, positive peritoneal cytology, old age (>77 years), obesity (body mass index ≥30 kg/m²), and diabetes.

Results A relapse was diagnosed in 98 patients (10.5%) (vaginal in 15, pelvic in 27, intra-abdominal beyond the pelvis in 27, extra-abdominal in 29). None of the variables were associated with an altered risk of vaginal or pelvic relapses in univariate analyses. Poor differentiation, myometrial invasion 50% or greater, tumor size 3 cm or greater, and positive peritoneal cytology were associated with an increased risk of intra-abdominal relapses beyond the pelvis (odds ratios [ORs] between 2.2 and 9.6). With the exception of obesity and diabetes, all variables were associated with an increased risk of extra-abdominal relapses (ORs between 2.3 and 13). Tumor size 3 cm or greater (OR, 3.1) and positive peritoneal cytology (OR, 16) predicted intra-abdominal relapses beyond the pelvis in multivariate analysis, whereas poor differentiation (OR, 2.9), myometrial invasion 50% or greater (OR, 4.0), and positive peritoneal cytology (OR, 27) predicted extra-abdominal relapses. Compared with vaginal relapses, intra-abdominal relapses beyond the pelvis and extra-abdominal relapses were associated with a worse disease-specific survival. Survival of patients with a pelvic relapse did not differ from that of patients with a vaginal relapse.

Conclusions Risk variables of endometrial cancer are differently associated with relapses in different locations. Our findings may promote studies that explore the most efficient adjuvant therapy in high-risk early-stage endometrioid endometrial cancer.