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

OBJECTIVES

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.

MATERIALS AND METHODS

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.

RESULTS

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).

CONCLUSION

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.