Retrospective analyses of false-positive ۲-[۱۸F]FDG PET/CT lymph node findings in patients with papillary thyroid cancer

Introduction: There are inconsistent results of studies on accuracy of ۲-[۱۸F]fluoro-۲-deoxy-D-glucose-positron emission tomography/computed tomography (۲-[۱۸F]FDG-PET/CT) for cervical lymph node (LN) staging. The aim of this study is to evaluate the accuracy of ۲-[۱۸F]FDG-PET/CT in the cervical LN staging of patients with papillary thyroid cancer (PTC) and the factors associated with false-positive LNs in these patients.Methods: A total of ۲۳۴ patients with pathologically proven PTC, who underwent ۲-[۱۸F]FDG-PET/CT for staging from January ۲۰۱۱ to December ۲۰۱۴, were analyzed. The gold standard for diagnosing LN is a combination of surgical pathology and clinical follow-up. Nodal uptake with a maximum standardized uptake value (SUVmax) > ۲.۰ was interpreted as PET/CT-positive.Results: The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of ۲-[۱۸F]FDG-PET/CT in detecting cervical LN metastases were ۴۲.۷% (۴۱/۹۶), ۷۷.۷% (۲۴۸/۳۱۹), ۳۶.۶% (۴۱/۱۱۲), ۸۱.۹% (۲۴۸/۳۰۳), and ۶۹.۶% (۲۸۹/۴۱۵), respectively. The incidence of false-positive LN metastases was ۶۳.۴% (۷۱ of ۱۱۲ LNs). The factors significantly associated with false positives were age < ۴۵ years old (p = ۰.۰۳۲) and SUVmax of the primary tumor < ۴.۰ (p = ۰.۰۲۱). In addition, false-positive LNs were correlated with a low LN SUVmax, location (central vs. lateral), and direction (ipsilateral vs. contralateral).Conclusion: These findings suggest that cervical LN staging by ۲-[۱۸F]FDG-PET/CT in PTC patients should be more carefully assessed in patients younger than ۴۵ years old with a primary tumor SUVmax < ۴.۰ or contralateral LN.

Keywords:

۲-[۱۸F]FDG-PET/CT , False-positive lymph node , Papillary thyroid cancer