# [18F]FDG PET/MRI in Endometrial Cancer: Prospective Evaluation of Preoperative Staging, Molecular Characterization and Prognostic Assessment

## TL;DR

This study shows that [18F]FDG PET/MRI is highly accurate for staging endometrial cancer and predicting tumor aggressiveness and recurrence.

## Contribution

Demonstrates the novel use of hybrid [18F]FDG PET/MRI for molecular characterization and risk stratification in endometrial cancer.

## Key findings

- PET/MRI achieved 98.75% accuracy for primary tumor detection and 92.41% for lymph node detection.
- PET/MRI parameters predicted molecular alterations like p53 abnormalities and MMR deficiency.
- Tumor size and metabolic volume were linked to higher recurrence risk (p < 0.001).

## Abstract

This prospective study evaluated the value of hybrid [18F]FDG PET/MRI in supporting risk stratification of endometrial cancer (EC). The cohort included 80 women with newly diagnosed EC, who underwent [18F]FDG PET/MRI before surgery and were followed for recurrence. PET/MRI showed excellent diagnostic accuracy for both primary tumor detection and lymph node assessment. Multiparametric PET/MRI features were analyzed and predicted several indicators of tumor aggressiveness such as the molecular alterations of p53 abnormalities and MMR deficiency recently introduced in the updated FIGO staging system and the clinical indicators of relapse risk and need for adjuvant therapy. Overall, PET/MRI demonstrated meaningful potential for predicting tumor behavior and improving risk stratification and personalized treatment planning in endometrial cancer patients.

Background/Objectives: Early and accurate characterization of endometrial cancer (EC) is crucial for patient management, but current imaging modalities lack in diagnostic accuracy and ability to assess molecular profiles. The aim of this study is to evaluate hybrid [18F]FDG PET/MRI’s diagnostic accuracy in EC staging and role in predicting tumor aggressiveness, molecular characterization, and recurrence. Methods: A prospective study (ClinicalTrials.gov, ID:NCT04212910) evaluating EC patients undergoing [18F]FDG PET/MRI before surgery (2018–2024). Histology, immunohistochemistry, and patients’ follow-up (mean FU time: 3.13y) were used as the reference standard. [18F]FDG PET/MRI, PET only, and MRI only were independently reviewed to assess the diagnostic accuracy (ACC), sensitivity (SN), specificity (SP), and positive/negative predictive value (PPV, NPV). Imaging parameters were extracted from [18F]FDG PET and pcT1w, T2w, DWI, and DCE MRI. Spearman’s correlations, Fisher’s exact test, ROC-AUC analysis, Kaplan–Meier survival curves, log-rank tests and Cox proportional hazards models were applied. Results: Eighty participants with primary EC (median age 63 ± 12 years) were enrolled, with 17% showing LN involvement. [18F]FDG PET/MRI provided ACC = 98.75%, SN = 98.75%, and PPV = 100% for primary tumor detection, and ACC = 92.41%, SN = 84.62%, SP = 93.94%, PPV = 73.33%, and NPV = 96.88% for LN detection. PET/MRI parameters predicted LN involvement (AUC = 79.49%), deep myometrial invasion (79.78%), lymphovascular space invasion (82.00%), p53abn (71.47%), MMRd (74.51%), relapse (82.00%), and postoperative administration of adjuvant therapy (79.64%). Patients with a tumor cranio-caudal diameter ≥ 43 mm and MTV ≥ 13.5 cm3 showed increased probabilities of recurrence (p < 0.001). Conclusions: [18F]FDG PET/MR showed exceptional accuracy in EC primary tumor and LN detection. Derived parameters demonstrated potential ability in defining features of aggressiveness, molecular alterations, and tumor recurrence.