title: Superiority of delayed risk stratification in differentiated thyroid cancer after total thyroidectomy and radioactive iodine ablation.
abstract: OBJECTIVE
  The aim of this study was to validate the effectiveness of delayed risk stratification (DRS) in predicting structural progression and compare the predictive value of American Thyroid Association (ATA) risk stratification with that of DRS in patients with differentiated thyroid cancer (DTC).
  
  
  METHODS
  A total of 398 patients with DTC who underwent surgery followed by radioactive iodine ablation were enrolled. Patients were categorized as having excellent response, acceptable response, biochemical incomplete response, or structural incomplete response at 8-15 months' evaluation after radioactive iodine ablation for DRS. Effectiveness of DRS was evaluated according to structural progression-free survival (PFS; median follow-up, 10.7 years).
  
  
  RESULTS
  A total of 229 patients (57.5%) were classified as having excellent response, 78 (19.6%) as having acceptable response, 62 (15.6%) as having biochemical incomplete response, and 29 patients (7.3%) as having structural incomplete response. After DRS, 60.2% of intermediate-risk patients and 20.5% of high-risk patients were shifted to the excellent response category. Sixty-nine patients (17.3%) showed structural progression. DRS showed statistical difference in PFS (hazard ratio, 4.268; 95% confidence interval, 3.258-5.477; P<0.001). In multivariate analysis of ATA risk stratification and DRS, DRS was significantly associated with PFS (hazard ratio, 4.383; 95% confidence interval, 3.250-5.912; P<0.001), but ATA risk stratification was not. There was no significant difference in deviances between the use of DRS alone and the use of both DRS and ATA risk stratification (χ=0.103, d.f.=1, P=0.748).
  
  
  CONCLUSIONS
  DRS is superior to ATA risk stratification in predicting structural disease progression for DTC patients.
authors.affiliation: aDepartment of Nuclear Medicine, Kyungpook National University School of Medicine and Hospital bCenter of Biostatistics, School of Medicine, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Chae Moon
authors.initials: CM
authors.lastname: Hong
authors.forename: Won Kee
authors.initials: WK
authors.lastname: Lee
authors.forename: Shin Young
authors.initials: SY
authors.lastname: Jeong
authors.forename: Sang-Woo
authors.initials: SW
authors.lastname: Lee
authors.forename: Byeong-Cheol
authors.initials: BC
authors.lastname: Ahn
authors.forename: Jaetae
authors.initials: J
authors.lastname: Lee
mesh_terms: D055011:Ablation Techniques; D018572:Disease-Free Survival; D023381:Endpoint Determination; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D018570:Risk Assessment / Q000379:methods*; D013964:Thyroid Neoplasms / Q000473:pathology / Q000601:surgery*; D013965:Thyroidectomy; D016896:Treatment Outcome
chemical_list: D007457:Iodine Radioisotopes