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 predicts overall survival (log-rank, p = 0.009). 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 recurrence. Conclusions MI depth of more than 1 cm is a valid indicator of patient outcome. Additionally, a cutoff of 33% MI probably has a better prognostic value than the current cutoff 50%.