title: The clinical impact of 18F-FDG PET in papillary thyroid carcinoma with a negative 131I whole body scan: a single-center study of 108 patients.
abstract: OBJECTIVE
  To assess whether FDG PET could localize the recurrent or metastatic lesions in papillary thyroid cancer patients with negative radioiodine scan.
  
  
  METHODS
  Whole body PET was performed after injecting 370-555 MBq of 18F-FDG in 108 patients, who were suspected of having recurrence or metastasis and whose 131I whole body scans were negative. Recurrence or metastasis occurred in 63 patients by pathology or clinical assessment, whereas 45 patients remained in remission.
  
  
  RESULTS
  FDG PET revealed recurrence or metastases in 59 patients (sensitivity 93.7%), whereas thyroglobulin (Tg) levels were elevated in 41 (sensitivity 65.1%). In 35 of 45 patients in remission, FDG PET was negative (specificity 77.8%). When patients positive for antithyroglobulin antibody were excluded, the sensitivity and specificity of serum Tg became 84.8% and 46.9%, respectively. Compared to Tg measurement, FDG PET detected more metastatic lesions in cervical lymph nodes. Of 40 patients with a negative radioiodine scan showing diffuse hepatic uptake, metastases occurred in 23 patients and remission in 17. FDG PET showed 100% sensitivity and 76.5% specificity in the detection of recurrence in these 40 patients.
  
  
  CONCLUSIONS
  FDG PET is useful for localizing recurrent or metastatic lesions in 131I scan-negative thyroid cancer patients. In particular, it is superior to serum Tg measurement for identifying metastases to cervical lymph nodes. We recommend its use in cases of negative radioiodine scan with diffuse hepatic uptake.
authors.affiliation: Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Mi-Yeon
authors.initials: MY
authors.lastname: Choi
authors.forename: June-Key
authors.initials: JK
authors.lastname: Chung
authors.forename: Ho-Yeong
authors.initials: HY
authors.lastname: Lee
authors.forename: Young
authors.initials: Y
authors.lastname: So
authors.forename: Do Joon
authors.initials: DJ
authors.lastname: Park
authors.forename: Jae Min
authors.initials: JM
authors.lastname: Jeong
authors.forename: Dong Soo
authors.initials: DS
authors.lastname: Lee
authors.forename: Myung Chul
authors.initials: MC
authors.lastname: Lee
authors.forename: Bo Youn
authors.initials: BY
authors.lastname: Cho
mesh_terms: D000328:Adult; D000368:Aged; D002277:Carcinoma / Q000175:diagnosis* / Q000000981:diagnostic imaging*; D002291:Carcinoma, Papillary / Q000175:diagnosis* / Q000000981:diagnostic imaging*; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D049268:Positron-Emission Tomography / Q000379:methods; D013954:Thyroglobulin / Q000737:chemistry; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging*; D051598:Whole Body Imaging
chemical_list: D007457:Iodine Radioisotopes; D019788:Fluorodeoxyglucose F18; D013954:Thyroglobulin