Preoperative predictive model of surgical planning in endometrial carcinoma using MRI and tumor grade in endometrial biopsy

Introduction: Endometrial cancer (EC) is the most common gynecological cancer in developed countries. Histological grade (G) and myometrial invasion (MI) are important risk factors, and together with the histological type and other postoperative data establish the risk of lymph node involvement and guide the adjuvant treatments. The objective of this study was to assess the validity of a preoperative stratification model that combines preoperative histological grade and MI as identified by magnetic resonance imaging (MRI) to select candidates for lymph node staging and optimize surgical planning for our patients. Material and methods: It´s an observational retrospective cohort study including 294 patients diagnosed with EC at Donostia University Hospital from January 2012 to December 2017. Preoperative endometrial biopsy, including histological type and grade, preoperative MRI was compared with the definitive histological diagnosis. Sensitivity (Sn), specificity (Sp), positive predictive value (PPV) and negative predictive value (NPV) of the MRI-based diagnosis were calculated. Results: After inclusion and exclusion criteria 242 cases of type I or II EC were analyzed. Our model was found to have a Se of 91.4% (95% CI 83.2-95.8) and a Sp of 90.7% (95% CI 85.2-94.3). Percentage of down staging was 6.2% (15 unnecessary lymphadenectomies) and the upstaging rate was 2.9%. The NPV of the model was very high (95.4%, 95% CI 90.9-97.8). The diagnostic odds ratio for our model was 147.95 (95% CI 52.9-410.5), with a diagnostic accuracy of 91.7% (95% 87.6-94.6). Conclusions: A preoperative strategy that includes the determination of the tumor grade based on an endometrial biopsy and an assessment of MI by MRI is of great help in pre-surgical planning for endometrial cancer surgery, allowing an extra peritoneal approach and optimizing the use of physical and human resources. MRI presents excellent discriminatory power in the detection of MI in EC, with no significant variation by pathological subtype.