The prognostic importance of features of myometrial invasion in endometrial endometrioid carcinoma

Purpose: The depth of myometrial invasion (MI) is known to have a prognostic value in endometrial carcinoma (EC), and the FIGO 50% cutoff is widely accepted; however, recent studies have suggested other measurements such as the absolute depth of invasion and tumor-free distance (TFD) from the serosal surface to also be predictive. The aim of this study was to assess the association between the FIGO cutoff and other measures with overall survival and disease-free survival of patients. Methods: This is a retrospective analysis of a cohort of 248 women diagnosed with stage I endometrioid endometrial carcinoma, treated at Soroka University Medical Center between 2006 and 2020. Clinical and pathological data were collected and analyzed. ROC analysis was used to define the best cutoffs in all three categories (MI, absolute depth and TDF). Survival analyses were then conducted using Kaplan–Meier curves, log-rank tests, and Cox proportional hazards regression. Results: Absolute myometrial invasion (MI) to the depth of 1 cm significantly predicted overall survival (log-rank, p = 0.009) in univariate analysis; however, this significance was not maintained in multivariate analysis. Additionally, a 33% MI cutoff demonstrated potential for better outcome prediction as compared to the commonly used 50% MI threshold, though it did not reach statistical significance. Tumor-free distance (TFD) from the serosal surface was not significantly associated with outcome. Conclusions: MI depth of more than 1 cm may serve as a meaningful prognostic indicator. Additionally, a cutoff of 33% MI probably has a better prognostic value than the current 50% cutoff. These findings show a promising direction for future research, emphasizing the need for larger cohorts and multicenter studies to confirm our findings.