124I Positron Emission Tomography/Computed Tomography Versus Conventional Radioiodine Imaging in Differentiated Thyroid Cancer: A Review

Background: Studies report a wide spectrum of 124 I positron emission tomography (PET)/computed tomography (CT) sensitivity and specificity in the detection of differentiated thyroid cancer (DTC) lesions. This study reviews the lesion detection rate of pretherapy 124 I PET/CT in different patient populations and further analyzes the factors necessary for a better detection on 124 I PET/CT. Methods: A literature search was performed using multiple different databases (MEDLINE, EMBASE, Northern Lights, and handsearching) covering 1996 to April 2018. Two reviewers reviewed and extracted study data for 124 I, 123 I, and 131 I scans in DTC. Results: This review includes 4 retrospective and 10 prospective studies in which 495 DTC patients underwent 124 I and 131 I imaging; no studies made comparisons with 123 I. In the reports that compared 124 I PET/CT with diagnostic 131 I scans, there were a total of 72 patients in whom 120 lesions were detected on 124 I imaging, whereas only 52 were detected on diagnostic 131 I scans. In publications that compared 124 I with post-therapy 131 I scans in 266 patients, 410 lesions were detected with 124 I PET, whereas 390 were detected on post-therapy 131 I scans. Based on 124 I PET/CT in six studies, TNM staging was revised in 15–21% of patients, and disease management was altered in 5–29% of patients. Conclusions: 124 I PET/CT is able to identify a greater number of foci compared with diagnostic 131 I scans. 124 I PET may have better detection compared with post-therapy 131 I scans in patients who are 131 I therapy naive, have less aggressive pathology, or do not have disseminated lung metastases. Additional metastatic lesion detection by 124 I PET may have a significant clinical impact in the management of patients before 131 I therapy in some patients.