PET-CT scans in recurrent or persistent differentiated thyroid cancer: is there added utility beyond conventional imaging?

Abstract

Integrated positron emission tomography (PET)-computed tomography (CT) may have advantages over conventional imaging in localizing recurrent or persistent differentiated thyroid cancer. A retrospective review of patients who underwent PET-CT scans was performed. Results were compared with contrast CT, magnetic resonance imaging, ultrasonography, and radioactive iodine (RAI) scans. Thirty patients (mean age, 49.9 ± 17 years) underwent 36 PET-CT scans, mostly for elevated thyroglobulin levels and negative RAI scans (30 scans). Fifty percent (18/36) of PET-CT scans showed increased uptake in the neck, 11 of 36 (31%) in the chest, 3 of 36 (8.3%) in bone, and 6 of 36 (16.6%) in other areas. PET-CT had overall sensitivity, specificity, and positive predictive values of 73.9%, 61.5%, and 77.3% respectively. To assess the added value of PET-CT, we focused on the 21 scans performed after conventional imaging in 20 patients. PET-CT provided additional information in 2 (10%) patients, both of whom were spared interventions. However, PET-CT underestimated extent of disease in 3 (15%) patients and led to unnecessary interventions in 3 (15%) additional patients. PET-CT has reasonable sensitivity in the detection of recurrent thyroid cancer. However, the added value of PET-CT may be seen only in a limited number of patients after good quality, conventional imaging. Further studies are needed to determine the most cost-effective approach to managing these patients.