Preoperative prediction of deep myometrial invasion and tumor grade for stage I endometrioid adenocarcinoma: a simple method of measurement on DWI

Objectives: To explore the utility of the tumor area ratio (TAR) for predicting deep myometrial invasion and tumor grade in stage I endometrioid adenocarcinoma (EEA). Methods: We retrospectively evaluated 86 patients with International Federation of Gynecology and Obstetrics (FIGO) stage I EEA. All patients underwent unenhanced contrast MRI and diffusion-weighted imaging (DWI) procedures. The volume and maximum area of the tumor and uterus were obtained, and the tumor volume ratio (TVR) and TAR were calculated. The Kruskal-Wallis test and Mann-Whitney U test were used to compare the differences in indexes (TVR and TAR) between the different tumor grades and between superficial and deep myometrial invasion. Results: The TVR and TAR values for deep myometrial invasion and high-grade EEA tumors were significantly higher than the values for superficial myometrial invasion and low-grade tumors (all p = 0.000). According to the receiver-operating characteristic (ROC) curve, the area under the curve (AUC) was significantly higher for TAR than for TVR for tumors with deep myometrial invasion (0.936 vs. 0.844, p = 0.045). However, no significant differences in the AUCs for TVR and TAR were observed between high- and low-grade tumors (0.865 vs. 0.863, p = 0.956). A TAR ≥ 34.6% predicted deep myometrial invasion in EEA with a sensitivity, specificity, and accuracy of 85.0%, 84.8%, and 86.0%, respectively. A TAR ≥ 38.9% predicted high-grade tumors with a sensitivity, specificity, and accuracy of 83.3%, 81.1%, and 82.6%, respectively. Conclusion: TAR is useful for predicting deep myometrial invasion and high-grade stage I EEA Key Points: • TAR is useful for predicting risk factors for EEA. • TAR is easy to obtain and has high accuracy. • TAR has excellent interobserver repeatability agreement (ICC range 95.1–99.6%).