Impact of the 2023 FIGO staging revision on MRI diagnostic accuracy in FIGO 2009 stage I endometrial cancer

This study aimed to evaluate the diagnostic performance of Magnetic Resonance Imaging (MRI) for staging patients with International Federation of Gynecology and Obstetrics (FIGO) stage I endometrial cancer, by comparing the original 2009 system with the revised 2023 system.

This retrospective study included 432 patients (mean age, 54.9 years) with histopathologically confirmed FIGO 2009 stage I endometrial cancer who underwent preoperative MRI. The patients were categorized into non-aggressive (n = 364; low-grade endometrioid histology) and aggressive (n = 68; grade 3 endometrioid or non-endometrioid histology, including serous, clear cell carcinoma, and carcinosarcoma) tumor groups. Preoperative MRI-based assessment of myometrial invasion was compared with histopathological results to assess the myometrial invasion depth, which was classified as no invasion, superficial invasion (< 50%), and deep invasion (≥ 50%). Diagnostic accuracy, sensitivity, specificity, and agreement of preoperative MRI-based staging determination were calculated for both FIGO 2009 and 2023 systems.

In non-aggressive tumors, the 2009 FIGO staging demonstrated superior accuracy (kappa 0.82, 95% CI 0.74-0.89) compared to the 2023 staging (kappa 0.66, 95% CI 0.59-0.74), with a statistically significant difference (p = 0.0029). MRI performance varied across invasion depths, with excellent diagnostic accuracy for deep myometrial invasion (sensitivity, 87.0%; specificity, 95.9%). For aggressive tumors, no significant difference was observed between the two staging systems (p = 0.160). Subgroup analysis demonstrated that the presence of lymphovascular space invasion did not result in statistically significant differences in diagnostic agreement between MRI and pathological staging (p = 0.452).

This study provides evidence that 2023 FIGO staging revisions present measurable challenges for MRI-based staging accuracy, particularly in the assessment of non-aggressive endometrial tumors confined to the uterus. Despite these challenges, MRI maintains reliable diagnostic performance for detecting deep myometrial invasion in uterus-confined disease, supporting its continued utility in preoperative staging protocols. KEY TAKE‑HOME: Radiologists should recognize the statistically significant reduction in diagnostic accuracy for detecting the absence of myometrial invasion under FIGO 2023 criteria, particularly in non-aggressive endometrioid tumors, and consider integrating complementary quantitative imaging parameters or molecular biomarkers to enhance the preoperative staging precision.