title: Prognostic value of post-thyroidectomy thyroglobulin levels in patients with differentiated thyroid cancer.
abstract: BACKGROUND
  Thyroglobulin is an excellent biological marker of persistent or recurrent thyroid cancer during long-term follow-up. Most studies investigated its diagnostic value but not its prognostic value over time. We aim to study the prognostic value of thyroglobulin levels early after total thyroidectomy, before iodine ablation.
  
  
  METHODS
  The study was based on the Rabin Medical Center registry of patients with non-medullary thyroid carcinoma. Data were collected on the clinical, laboratory, and outcome characteristics of 420 consecutive patients followed at our institution for whom early post-operative pre-ablation thyroglobulin values (baseline thyroglobulin) were available.
  
  
  RESULTS
  Patients were classified into 4 groups by baseline thyroglobulin level: 0-2, 2-10, 10-100, and >100 ng/ml. Higher levels were associated with a shift toward male gender (p=0.01), larger tumor size (p=0.02), and a more extensive disease (p<0.0001). They were also related to disease persistence and evidence of disease at last follow-up (p<0.0001). The 10 ng/ml cut-off level identified patients with persistent disease with a sensitivity and specificity of 73%, positive predictive value of 43%, and negative predictive value of 89%. On multivariate analysis, the following variables were predictive of persistent disease: baseline thyroglobulin level, male gender, lymph-node involvement, distant metastases, higher tumor invasiveness, and larger tumor size. However, the predictive power of baseline thyroglobulin level was relatively weak (odds ratio 1.002, 95% confidence interval 1.00-1.04).
  
  
  CONCLUSIONS
  In patients with well-differentiated thyroid cancer, a post-thyroidectomy thyroglobulin level <10 ng/ml is associated with a low probability of having persistent disease and can be used combined with other disease characteristics for decisions regarding treatment and follow-up.
authors.affiliation: Endocrine Institute, Rabin Medical Center, Beilinson Campus, Petach Tikva 49100, Israel.
authors.forename: A
authors.initials: A
authors.lastname: Polachek
authors.forename: D
authors.initials: D
authors.lastname: Hirsch
authors.forename: G
authors.initials: G
authors.lastname: Tzvetov
authors.forename: S
authors.initials: S
authors.lastname: Grozinsky-Glasberg
authors.forename: I
authors.initials: I
authors.lastname: Slutski
authors.forename: J
authors.initials: J
authors.lastname: Singer
authors.forename: R
authors.initials: R
authors.lastname: Weinstein
authors.forename: I
authors.initials: I
authors.lastname: Shimon
authors.forename: C A
authors.initials: CA
authors.lastname: Benbassat
mesh_terms: D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000097:blood*; D002454:Cell Differentiation / Q000502:physiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D011379:Prognosis; D011446:Prospective Studies; D012042:Registries; D012189:Retrospective Studies; D013954:Thyroglobulin / Q000097:blood*; D013964:Thyroid Neoplasms / Q000097:blood* / Q000473:pathology* / Q000601:surgery; D013965:Thyroidectomy
chemical_list: D014408:Biomarkers, Tumor; D013954:Thyroglobulin