Background: Fluorine 18-fluoro-2-deoxyglucose (FDG) positron emission tomography ((18)F-FDG PET) can be used to visualize metastases in patients with differentiated thyroid carcinoma that does not take up radioiodine ((131)I). This study was aimed at evaluating the feasibility of (18)F-FDG radio-guided surgery in patients with radioiodine-negative differentiated thyroid cancer.
Methods: Ten patients received a mean activity of 265 MBq of (18)F-FDG 30 minutes before operation. Radioactivity uptake (counts per second [cps], with a pretime of 10 seconds) in tumor and normal tissues was measured before and after resection.
Results: Patients with 1 to 5 foci detected by FDG-PET were included in the study. Six of these patients were injected with recombinant human thyroid-stimulating hormone (TSH) preoperatively. Abnormal findings detected by preoperative (18)F-FDG PET were also detected with the gamma probe in all patients. The mean tumor activity in vivo was 3,272 cps, and tumor-to-neck and tumor-to-shoulder ratios were, respectively, 1.40 and 1.73. Tumor resection was incomplete in 3 patients. When resection was complete, mean radioactivity at the tumor site was decreased by 22%. The ex vivo mean tumor-to-normal tissue ratio was 2.4. All positive tissues detected with the probe were confirmed histologically to be differentiated thyroid cancer. The surgeon's hands were exposed to 90 to 270 microSv.
Conclusions: These results show the feasibility and benefit of (18)F-FDG radio-guided surgery with a gamma probe in the management of differentiated thyroid cancer patients with radioiodine-negative recurrence.