Purpose: Pathological data suggest that the rate of oestrogen receptor (ER) expression in uterine sarcoma is significantly lower than in leiomyoma. The present study aimed to investigate whether ER expression using ER imaging agents for positron emission tomography (PET), of which the most successful has been 16α-[18F]-fluoro-17β-oestradiol (FES), is able to add useful information to the differential diagnosis of uterine sarcoma and leiomyoma in patients with positive or equivocal findings on [18F]fluorodeoxyglucose (FDG) PET.
Methods: A total of 76 patients with suspected uterine sarcoma based on ultrasound and magnetic resonance imaging findings from 2007 to 2010 were enrolled. Twenty-four of the present patients were referred for FES PET because of FDG PET findings that showed equivocal or positive FDG uptake. PET images were quantitatively evaluated with reference to histopathological findings. Receiver-operating characteristic analysis was performed to determine the optimal cutoff value to differentiate uterine sarcoma and leiomyoma.
Results: Of the 24 patients, 11 had a final diagnosis of uterine sarcoma, while 13 had leiomyoma. The sensitivity, specificity and accuracy of an FDG to FES standardized uptake value (SUV) ratio greater than 2.0 were significantly higher using Cochran's Q test (p=0.024) when compared with FDG PET greater than 3.0 alone (90.9 vs 81.8%, 92.3 vs 84.6% and 91.3 vs 83.3%, respectively).
Conclusion: Additional FES PET findings confirmed uterine sarcoma in 91.3% of a selected group of patients with equivocal or positive FDG uptake.