Evaluation of ¹⁸F-FDG PET/MRI, ¹⁸F-FDG PET/CT, MRI, and CT in whole-body staging of recurrent breast cancer

Abstract

Objectives: To compare the diagnostic performance of (18)F-fluordesoxyglucose positron emission tomography/magnetic resonance imaging ((18)F-FDG PET/MRI) with (18)F-FDG PET/computed tomography ((18)F-FDG PET/CT), MRI, and CT in whole-body staging of recurrent breast cancer.

Material and methods: Twenty-one consecutive patients (age 59.4 ± 11.5 years, range 38.5-76.9 years; 20 female, 1 male) with suspected breast cancer recurrence underwent a clinically indicated (18)F-FDG PET/CT and subsequently a (18)F-FDG PET/MRI examination in a single injection protocol (mean injected activity: 257 ± 44 MBq (18)F-FDG). Each (18)F-FDG PET/MRI, (18)F-FDG PET/CT, as well as the CT component of PET/CT (CTPET/CT) and MR images of PET/MRI (MRIPET/MRI) were separately evaluated by two radiologists regarding lesion count, lesion localization, and lesion categorization (benign/malignant). The reference standard was based on histopathological results as well as prior and follow-up imaging. A Wilcoxon test assessed differences in SUVmax between (18)F-FDG PET/MRI and (18)F-FDG PET/CT. Correlation of SUVmax between (18)F-FDG PET/MRI and (18)F-FDG PET/CT was calculated using Pearson's correlation coefficient. Interobserver agreement on dignity ratings was evaluated using Cohen's kappa.

Results: According to the reference standard, 17 patients had breast cancer recurrence. (18)F-FDG PET/MRI, (18)F-FDG PET/CT, and MRIPET/MRI correctly identified each of the 17 patients, whereas CTPET/CT correctly identified 15 of the 17 patients. A total of 134 lesions were described (116 malignant, 18 benign). (18)F-FDG PET/MRI detected all 134 lesions, of which (18)F-FDG PET/CT, MRIPET/MRI, and CTPET/CT detected 97.0%, 96.2%, and 74.6%, respectively. (18)F-FDG PET/MRI yielded the highest proportion of correctly categorized lesions (98.5%) compared with (18)F-FDG PET/CT (94.8%), MRIPET/MRI (88.1%), and CTPET/CT (57.5%). SUVmax was strongly correlated (r=0.72) but measured significantly higher on (18)F-FDG PET/MRI than on (18)F-FDG PET/CT in corresponding PET-positive lesions (SUVmax: 5.6 ± 2.8 vs. 4.9 ± 1.8; p=0.001). Interobserver agreement on lesion dignity was substantial with (18)F-FDG PET/MRI (k=0.65; p<0.001) and (18)F-FDG PET/CT (k=0.65; p<0.001). With MRIPET/MRI interobserver analysis yielded a moderate agreement (k=0.56; p<0.001), whereas there was only fair agreement evaluating the CTPET/CT datasets (k=0.31; p=0.002).

Conclusions: (18)F-FDG PET/MRI offered the highest diagnostic performance compared with (18)F-FDG PET/CT, MRI and CT. Thus, (18)F-FDG PET/MRI should be regarded as a valuable alternative in whole-body staging of recurrent breast cancer.

Keywords: Breast cancer; CT; MRI; PET/CT; PET/MRI; Recurrent.