The current and evolving role of FDG–PET/CT in personalized iodine-131 therapy of differentiated thyroid cancer

Purpose Several approaches have been recommended for the selection of patients with differentiated thyroid cancer amenable for postoperative radioiodine remnant ablation or repeated radioiodine treatment, though with inadequate results. 2-[18F]-fluoro-2-deoxy- d -glucose positron emission tomography is gaining consideration for predicting disease-free or survival of differentiated thyroid carcinoma patients, in particular in the peri-or post-surgery setting and for the detection of recurrence in patients with elevated or rising thyroglobulin without evidence of disease on neck ultrasound or iodine scintigraphy. This paper aims to review the role of FDG–PET/CT in tailoring iodine-131 empiric therapy for radioiodine remnant ablation and the detection of recurrence in patients with elevated thyroglobulin and negative iodine-123 scan. Methods A literature search up to May 2017 of MEDLINE® and SCOPUS® with the Mesh terms: “PET/CT”, “iodine-131 therapy”, “differentiated thyroid cancer” and “prognosis” was performed. Thereafter, papers dealing with radioiodine remnant ablation and empiric therapy were selected. Results Ninety papers were retrieved from the initial search and 19 considered for the review. The percentage of positive FDG–PET/CT performed at radioiodine remnant ablation or shortly after ranged from 17 to 69%, with highest values in high- and intermediate-to-high risk patients. The response rate to radioiodine remnant ablation and survival were consistently higher in negative FDG–PET/CT patients. Besides, FDG–PET/CT imaging was found to be a very accurate diagnostic tool for the detection of recurrence in patients with elevated thyroglobulin and negative iodine-123 scan, discriminating patients needing further empirical iodine-131 therapy from those who could benefit from alternative approaches. Conclusions Although a meta-analysis was not possible due to the heterogeneity and the small population samples of the studies retrieved, the results of the present review support the use of FDG–PET/CT in tailoring iodine-131 therapy when used close to radioiodine remnant ablation and in patients amenable to iodine-131 empiric therapy.