Assessment of the incremental value of recombinant thyrotropin stimulation before 2-[18F]-fluoro-2 - deoxy-D-glucose positron emission tomography/computed tomography imaging to localize residual differentiated thyroid cancer

Purpose: The purpose of the study was to assess prospectively the impact of recombinant human TSH (rhTSH) administration on positron emission tomography (PET)/computed tomography (CT) imaging in differentiated thyroid cancer patients who, after primary treatment, had a suppressed or stimulated serum thyroglobulin greater than 10 ng/ml and no radioactive iodine uptake consistent with thyroid cancer on a whole body scan. Patients and Methods: PET/CT was performed before (basal PET) and 24-48 h after rhTSH administration (rhTSH-PET) in 63 patients (52 papillary and 11 follicular thyroid cancers). Images were blindly analyzed by two readers. The proposed treatment plan was prospectively assessed before basal PET, after basal PET, and again after rhTSH-PET. Results: A total of 108 lesions were detected in 48 organs in 30 patients. rhTSH-PET was significantly more sensitive than basal PET for the detection of lesions (95 vs. 81%; P = 0.001) and tended to be more sensitive for the detection of involved organs (94 vs. 79%; P = 0.054). However, basal PET and rhTSH-PET did not have significantly different sensitivity for detecting patients with any lesions (49 vs. 54%; P = 0.42). Changes in treatment management plan occurred in 19% of the patients after basal PET. Lesions found only by rhTSH-PET contributed to an altered therapeutic plan in eight patients, among whom only four were true-positive on pathology (6%). Conclusion: The use of rhTSH for 2-[18F]-fluoro-2-deoxy-d-glucose-PET/CT significantly increased the number of lesions detected, but the numbers of patients in whom any lesion was detected were no different between basal and rhTSH-stimulated PET/CT scans. Treatment changes due to true positive lesions occurred in 6% of cases.