title: Detection of residual lymph node metastases in high-risk papillary thyroid cancer patients receiving adjuvant I-131 therapy: the usefulness of F-18 FDG PET/CT.
abstract: OBJECTIVE
  The aims of this retrospective study were to evaluate the incidence of residual lymph node (LN) metastases in high-risk papillary thyroid cancer (PTC) patients receiving adjuvant I-131 therapy, especially in those without I-131 accumulation, and to evaluate the clinical usefulness of F-18 FDG PET/CT to detect those lesions.
  
  
  METHODS
  The 37 PTC patients receiving adjuvant I-131 therapy were retrospectively evaluated. We examined the incidence of residual LN metastasis and compared the accumulation of F-18 FDG and I-131 in those lesions, and compared the serum thyroglobulin (Tg) levels between patients with and without residual LN metastases.
  
  
  RESULTS
  A total of 33 lesions were diagnosed as residual LN metastases in 9 patients. FDG accumulated in all of the lesions, but 19 lesions (57.6%) of them had no I-131 accumulation. The SUVmax was significantly higher in lesions without I-131 accumulation than in lesions with I-131 accumulation (6.6 +/- 2.8 vs. 4.2 +/- 1.8; P = 0.007). The serum Tg levels were significantly higher in patients with residual LN metastases than in patients without it (709.9 +/- 1470.8 vs. 25.6 +/- 37.1 ng/mL; P = 0.005). The incidence of residual LN metastasis was significantly higher in patients with a detectable serum Tg level than in patients without it (35.0% vs. 0%, P = 0.03).
  
  
  CONCLUSIONS
  These results indicate that the residual LN metastasis was relatively common in high-risk PTC patients receiving adjuvant I-131 therapy whose serum Tg levels remained detectable, and those lesions often had no I-131 accumulation. FDG-PET/CT would be recommended for PTC patients with detectable serum Tg levels to detect residual LN metastases.
authors.affiliation: Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan. kkaneko-kyu@umin.ac.jp
authors.forename: Koichiro
authors.initials: K
authors.lastname: Kaneko
authors.forename: Koichiro
authors.initials: K
authors.lastname: Abe
authors.forename: Shingo
authors.initials: S
authors.lastname: Baba
authors.forename: Takuro
authors.initials: T
authors.lastname: Isoda
authors.forename: Hidetake
authors.initials: H
authors.lastname: Yabuuchi
authors.forename: Masayuki
authors.initials: M
authors.lastname: Sasaki
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Hatakenaka
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Honda
mesh_terms: D000328:Adult; D000368:Aged; D002291:Carcinoma, Papillary / Q000175:diagnosis / Q000532:radiotherapy* / Q000556:secondary*; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis / Q000532:radiotherapy; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D018714:Radiotherapy, Adjuvant; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18