Hybrid PET/MRI in Staging Endometrial Cancer: Diagnostic and Predictive Value in a Prospective Cohort

Abstract Purpose. Assessment of deep myometrial invasion (MI) and lymphovascular space invasion (LVSI) is of utmost importance in preoperative staging of endometrial cancer (EC). Imaging parameters derived respectively from MRI and PET have shown good predictive value. Aim of the present study is to assess the diagnostic performance of hybrid 18F-FDG PET/MRI in EC staging, with particular focus on MI and LVSI detection.Methods. Prospective monocentric study including 35 patients with biopsy-proven EC undergoing preoperative 18F-FDG PET/MRI for staging purpose. Histological examination was the reference standard. PET (SUVmax, SUVmean40, MTV40, TLG40) and MRI (volume index-VI, total tumor volume-TTV, tumor volume ratio-TVR, ADCmean, ADCmin) parameters were calculated on the primary tumor, and their role in predicting histological findings (grade, high- vs. low-risk groups, LVSI, MI, p53 hyper-expression) was assessed through a ROC analysis.Results. 18F-FDG-PET/MRI identified the primary tumor in all patients. In the LVSI detection, PET/MRI demonstrated high accuracy, specificity and negative predictive value (sensitivity=0.8571, specificity=0.9286, accuracy=0.9143, NPV=0.9630, PPV=0.7500). Assessment of MI using PET/MRI correctly staged 27 patients, showing a good positive predictive value (77.1%; sensitivity= 0.7273, specificity=0.8462, accuracy=0.7714, PPV=0.8889, NPV=0.647). VI, TTV, and TVR significantly predicted risk groups (p=0.0059, 0.0235, 0.0181, respectively). VI, TTV, TVR, MTV40 and TLG40 significantly predicted LVSI (p=0.0023, 0.0068, 0.0068, 0.0027, 0.0139, respectively). Imaging was not able to predict grading, MI nor p53 hyper-expression.Conclusion. 18F-FDG-PET/MRI has good accuracy in preoperative staging of EC; PET and MRI parameters have synergic role in preoperatively predicting LVSI, with MRI parameters being also predictive for EC risk groups.