Comparison of 18F-FDG PET/MRI and MRI alone for whole-body staging and potential impact on therapeutic management of women with suspected recurrent pelvic cancer: a follow-up study.

PURPOSE: To evaluate the diagnostic performance of 18F-FDG PET/MRI for whole-body staging and potential changes in therapeutic management of women with suspected recurrent pelvic cancer in comparison with MRI alone. METHODS: Seventy-one consecutive women (54 ± 13 years, range: 25-80 years) with suspected recurrence of cervical (32), ovarian (26), endometrial (7), vulvar (4), and vaginal (2) cancer underwent PET/MRI including a diagnostic contrast-enhanced MRI protocol. PET/MRI and MRI datasets were separately evaluated regarding lesion count, localization, categorization (benign/malignant), and diagnostic confidence (3-point scale; 1-3) by two physicians. The reference standard was based on histopathology results and follow-up imaging. Diagnostic accuracy and proportions of malignant and benign lesions rated correctly were retrospectively compared using McNemar's chi2 test. Differences in diagnostic confidence were assessed by Wilcoxon test. RESULTS: Fifty-five patients showed cancer recurrence. PET/MRI correctly identified more patients with cancer recurrence than MRI alone (100% vs. 83.6%, p < 0.01). In contrast to PET/MRI, MRI alone missed 4/15 patients with pelvic recurrence and miscategorized 8/40 patients with distant metastases as having local recurrence only. Based on the reference standard, 241 lesions were detected in the study cohort (181 malignant, 60 benign). While PET/MRI provided correct identification of 181/181 (100%) malignant lesions, MRI alone correctly identified 135/181 (74.6%) malignant lesions, which was significantly less compared to PET/MRI (p < 0.001). PET/MRI offered superior diagnostic accuracy (99.2% vs. 79.3%, p < 0.001) and diagnostic confidence in the categorization of malignant lesions compared with MRI alone (2.7 ± 0.5 vs. 2.4 ± 0.7, p < 0.001). CONCLUSION: PET/MRI demonstrates excellent diagnostic performance and outperforms MRI alone for whole-body staging of women with suspected recurrent pelvic cancer, indicating potential changes in therapy management based on evaluation of local recurrence and distant metastatic spread.