Clinical Usefulness of F-18 FDG PET/CT in Papillary Thyroid Cancer with Negative Radioiodine Scan and Elevated Thyroglobulin Level or Positive Anti-thyroglobulin Antibody

Su Jung Choi; Kyung Pyo Jung; Sun Seong Lee; Yun Soo Park; Seok Mo Lee; Sang Kyun Bae

doi:10.1007/s13139-015-0378-5

Clinical Usefulness of F-18 FDG PET/CT in Papillary Thyroid Cancer with Negative Radioiodine Scan and Elevated Thyroglobulin Level or Positive Anti-thyroglobulin Antibody

Nucl Med Mol Imaging. 2016 Jun;50(2):130-6. doi: 10.1007/s13139-015-0378-5. Epub 2015 Oct 22.

Authors

Su Jung Choi¹, Kyung Pyo Jung¹, Sun Seong Lee¹, Yun Soo Park¹, Seok Mo Lee¹, Sang Kyun Bae²

Affiliations

¹ Department of Nuclear Medicine, Busan Paik Hospital, Inje University College of Medicine, 75 Bokji-ro, Busanjin-gu, Busan, Korea.
² Department of Nuclear Medicine, Haeundae Paik Hospital, Inje University College of Medicine, 875 Haeun-daero, Haeundae-gu, Busan, Korea.

Abstract

Purpose: Elevated thyroglobulin (Tg) levels, along with a negative radioiodine scan, present a clinical problem for the diagnosis of recurrence in papillary thyroid cancer (PTC) patients. The purpose of this study was to assess (1) the usefulness of (18)F-fluorodeoxyglucose (F-18 FDG) positron emission tomography (PET)/computed tomography (CT) for PTC patients with negative diagnostic radioiodine scan and elevated serum Tg level or positive anti-thyroglobulin antibody (TgAb), and (2) the effect of endogenous thyroid stimulating hormone (TSH) stimulation (ETS) on detecting recurrence in these circumstances.

Methods: Eighty-four patients with negative diagnostic radioiodine scan and elevated serum Tg or positive TgAb under ETS were included. Correlation with clinicopathological features and recurrence, detectability of FDG PET/CT and cut-off value of serum Tg for recurrence in PTC patients with these circumstance were assessed. In addition, detectability of F-18 FDG PET/CT under ETS and suppression were compared.

Results: In Cox regression analysis, only serum Tg level was significantly associated with recurrence (P < 0.001, HR = 1.13; 95 % CI, 1.061-1.208). The cut-off level of Tg was 21.5 ng/mL (AUC, 0.919; P < 0.001) for discriminating the recurrence in the patients with positive PET/CT finding. The sensitivity, specificity, PPV, NPV, and accuracy of F-18 FDG PET/CT for detecting recurrence were 64 %, 94 %, 86 %, 81 %, and 83 %. In the analysis of F-18 FDG PET/CT under ETS, the sensitivity, specificity, PPV, NPV and accuracy was 64 %, 94 %, 88 %, 81 % and 83 %. Those under TSH suppression were 67 %, 92 %, 80 %, 85 % and 83 %.

Conclusions: F-18 FDG PET/CT, although less sensitive, showed high specificity, PPV, NPV, and accuracy and therefore can be useful for the patients with negative diagnostic radioiodine scan and elevated serum Tg or positive TgAb. In addition, FDG PET/CT under ETS does not seem to have an additive role in detecting recurrence in these patients.

Keywords: FDG; PET/CT; Papillary thyroid cancer; Thyroglobulin; Thyroid stimulating hormone.