Introduction/Background In patients with early-stage, grade 1–2, endometrioid endometrial cancer, preoperative assessment of myometrial invasion is essential to define the need of pelvic and paraaortic lymph node dissection. Our aim was to evaluate the role of three-dimensional transvaginal ultrasound (3D-TVUS) and diffusion-weighted magnetic resonance imaging (DW-RMI) for the assessment of myometrial invasion in patients with low-risk endometrial cancer.

Methodology We performed a single center retrospective study, including patients who underwent surgery for grade 1–2 endometrioid endometrial cancer, FIGO stage I-II, in Hospital Clínic de Barcelona between 2010 and 2019. We computed sensitivity, specificity, and predictive values of 3D-TVUS and DW-RMI, as well as of intraoperative frozen section pathological study of surgical specimen, for diagnosis of deep myometrial invasion (≥50%). Definitive pathological analysis of surgical specimen was considered gold standard for diagnosis of deep myometrial invasion.

Results One hundred and fifty-three patients were included, 120 (78.43%) patients presented myometrial invasion <50% in postoperative analysis of surgical specimen and 33 (21.57%) patients presented deep myometrial invasion. Sensitivity and specificity of 3D-TVUS for diagnosis of deep myometrial invasion was 68.8% and 80.5% respectively, while DW-RMI showed a sensitivity and specificity of 76.2% and 84.4%. When combining both techniques (we considered that a patient had deep myometrial invasion when 3D-TVUS or DW-RMI – or both of them – showed deep myometrial invasion), sensitivity was 93.1% and specificity was 68.4%. The proportion of patients with uterine fibroids was higher in the group of patients with false negative (60%) or false positive (39.13%) result in 3D-TVUS, although these results did not reach statistical significance. Regarding the intraoperative frozen section pathological study of surgical specimen, it showed a sensitivity of 75% with specificity of 96.4% for diagnosis of deep myometrial invasion.

Conclusion The combination of 3D-TVUS and DW-RMI offers a better sensitivity, higher than intraoperative frozen section pathological study of the surgical specimen, for the diagnosis of deep myometrial invasion in patients with early-stage, grade 1–2, endometrioid endometrial cancer. Such information may be useful in selecting patients who require lymph node dissection.

Disclosures The authors of this abstract have no disclosures.