Detection of Thyroid Cancer by an FDG-PET Cancer Screening Program: A Japanese Nation-wide Survey

Background/Aim: The [F-18]-fluorodeoxyglucose positron emission tomography (FDG-PET) cancer screening program is defined as a cancer screening for asymptomatic subjects using FDG-PET (including PET/ computed tomography [CT]) with or without combination of other screening tests. The aim of the present study was to analyze the thyroid cancer detection rate in asymptomatic individuals through a FDG-PET cancer screening program in Japan. Materials and Methods: A total of 153,775 asymptomatic individuals underwent FDG-PET cancer screening. We analyzed 1,308 cases for possible thyroid cancer in all screening tests. Results: Among the 1,308 possible cases, 353 were verified as thyroid cancer. The relative sensitivity and positive predictive value (PPV) of FDG-PET were 90.7% and 29.5% for thyroid cancer, respectively. The relative sensitivity was equivalent to thyroid ultrasonography (US) (90.9%) and higher than neck computed tomography (CT) (75.7%, p<0.001), thyroglobulin (36.1%, p<0.001), and carcinoembryonic antigen (5.6%, p<0.001). The sensitivity with a PET/CT scanner was higher than that with a dedicated PET scanner (94.1% vs. 85.0%, p<0.001). Combining thyroid US with FDG-PET increased the relative sensitivity and PPV. The majority of thyroid carcinomas detected by FDG-PET screening were Union for International Cancer Control (UICC) stage I, but a significant number of cases were also detected as stage III or IV Conclusion: The FDG-PET cancer screening program in Japan detected thyroid cancer at an early stage. FDG-PET showed high sensitivity in detecting thyroid cancer, and it may be more effective if combined with thyroid US.