Abstract
Initial treatment for differentiated thyroid carcinoma (DTC) often consists of
surgery and the administration of radioiodine. In this context, post-treatment
Whole-Body Scans (ptWBS) are currently recommended, but data on its diagnostic
accuracy are rare. The aim of the study was to evaluate the performance of ptWBS
for distant metastasis in DTC patients. We included DTC patients who received
radioiodine and underwent ptWBS between 2009–2015. The medical data were
independently reviewed by two specialists to evaluate the concordance of
positive distant ptWBS uptake and distant metastasis documented by imaging exams
(gold standard). We studied 268 DTC patients. The mean age was 46±16
years (82% women), and papillary thyroid carcinoma was diagnosed in
87% of the patients. The median tumor size was 2.7 cm,
40% had lymph node involvement, and 11% had distant metastasis.
Twenty-eight patients (10%) had distant ptWBS uptake, and nine of them
(32%) were false-positives. In addition, nine false-negative ptWBS
uptakes were identified. The overall performance of ptWBS showed 68%
sensitivity and 96% specificity with significantly different performance
according to the American Thyroid Association (ATA) risk groups. While the ptWBS
performance for ATA low-intermediate-risk showed 29% sensitivity,
97% specificity, and Kappa of 0.19, the ATA high-risk group ptWBS
displayed high sensitivity (82%), specificity (100%), and good
agreement (Kappa 0.74). ptWBS is useful for a subgroup of ATA high-risk DTC
patients. The overall poor performance of ptWBS suggests that it should be
reconsidered for routine use in ATA at low to intermediate risk: the exam has
little value to this subgroup.
Key words
differentiated thyroid carcinoma - whole-body scan - radioiodine - prognosis - false-positive
