Abstract
1589
Objectives Significant uptake of the prostate is often identified as an incidental finding on whole-body Fluroine-18 fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) for non-prostate disease. The aim of this study was to investigate the prevalence of incidental 18F-FDG uptake in PET/CT and risk of cancer, usefulness of 18F-FDG uptake pattern, SUVmax, CT findings, and to define the predictable variables.
Methods A total of 11,239 male non-prostate disease patients who underwent 18F-FDG PET/CT study from November 2006 to June 2011 were included retrospectively. They were divided into two groups: 9,364 patients for metastatic evaluation, 1,875 patients for cancer screening. When incidental prostate FDG uptake was found, further diagnostic examination was conducted.
Results In our institution, the prevalence of incidental prostate FDG uptake was approximately 1.8% (198/11,239). The prevalence in healthy subjects (68/1,875; 3.6%) was statistically higher than that in patients with suspected or known cancer (130/9,364) (P<0.05). Among 198 incidental lesions, 100 patients had further examinations; 20 lesions were confirmed to be malignant while 80 lesions were benign. Therefore, the cancer risk of incidental FDG uptake in prostate was 20.0% (20/100). After logistic regression analysis, among the various variables of 18F-FDG PET/CT, age, site and uptake pattern were the potent predictors for differentiation of malignant prostate lesions. Although SUVmax was higher in malignant lesions (P<0.01), but there was still a great overlap. The best cut-off value of SUVmax for differentiation was 4.55; but with a low sensitivity of 65.0% and specificity of 68.7%.
Conclusions The presence of incidental patchy FDG uptake in peripheral zone of the prostate in an elder man correlates with high likelihood of malignancy. Under this circumstance, further evaluation should be recommended.