Recurrence detection in differentiated thyroid cancer patients with elevated serum level of antithyroglobulin antibody: special emphasis on using ¹⁸F-FDG PET/CT

다국어 초록 (Multilingual Abstract)

<P>Summary</P><P>Objective </P><P>A clinical challenge is presented by differentiated thyroid cancer (DTC) patients who show increased serum antithyroglobulin antibody (TgAb) level with undetectable thyroglobulin (Tg) and negative radioiodine whole body scan (I-WBS). The aim of this study is to investigate the recurrence in DTC patients with elevated TgAb by using <SUP>18</SUP>F-FDG PET/CT (PET/CT) in addition to I-WBS and neck ultrasonography (USG).</P><P>Subjects and design </P><P>A total of 276 TgAb+ patients were enrolled. Recurrence was assessed and compared between TgAb+ and TgAb- patients. TgAb+ patients were further categorized into two groups of 35–140 U/ml (Group A) and 140 U/ml or greater (Group B), according to receiver operating characteristic (ROC) curve analysis. Tumoural status was evaluated regarding the TgAb positivity and the degree of increase of TgAb.</P><P>Results </P><P>Thirty-seven (13·4%) of 276 TgAb+ patients were finally diagnosed with recurrence, compared with 21 (13·5%) of 156 TgAb- patients (<I>P</I> = 0·987). There was a correlation between TgAb level and recurrence (<I>P</I> = 0·032). Recurrence was more common in Group B than Group A (27·8% and 9·9%, respectively, <I>P</I> = 0·001). Recurrence was found in 37·5% of 24 TgAb+/Tg- patients who showed a gradually increasing tendency in serial measurements of TgAb. Sixteen cervical foci (21·1%) missed on neck USG and 17 lesions (22·4%) located outside the neck were additionally detected with PET/CT in TgAb+ patients.</P><P>Conclusions </P><P>TgAb plays a complementary role to Tg in the detection of recurrence of DTC. Tumour recurrence was more frequent in patients with elevated TgAb level over 140 U/ml or a trend toward increasing levels. PET/CT could provide additional information to I-WBS and neck USG in detecting tumour recurrence in patients with elevated TgAb.</P>