title: Thyroid cancer recurrence in patients clinically free of disease with undetectable or very low serum thyroglobulin values.
abstract: METHODS
  This was a retrospective clinical study.
  
  
  METHODS
  The study was conducted at a university-based tertiary cancer hospital.
  
  
  METHODS
  One hundred seven patients had initial thyroid cancer surgery and subsequent remnant radioiodine ablation. Patients underwent recombinant human TSH (rhTSH)-mediated diagnostic whole-body scan and rhTSH-stimulated thyroglobulin (Tg) measurement before April 2001 if they had no antithyroglobulin antibodies, were clinically free of disease, and had one or more undetectable (≤0.5 ng/ml) or low (0.6-1 ng/ml) basal Tg measurements on levothyroxine. Patients were stratified according to their rhTSH-Tg responses: group 1, Tg 0.5 ng/ml or less (68 patients); group 2, Tg from 0.6 to 2.0 ng/ml (19 patients); and group 3, Tg greater than 2 ng/ml (20 patients).
  
  
  METHODS
  Tumor recurrence was measured.
  
  
  RESULTS
  In group 1, two of 62 patients (3%) with follow-up recurred. In group 2, 63% converted to group 1, whereas two of 19 (11%) converted to group 3 and then recurred. Sixteen of the initial 20 group 3 patients (80%) recurred, including recurrence rates of 69 and 100% for those with an initial rhTSH-Tg greater than 2.0 ng/ml but 5.0 ng/ml or less, and 4.6 ng/ml or greater, respectively. One group 3 patient died of distant metastases. rhTSH-Tg more accurately predicted tumor recurrence than basal Tg. An rhTSH-Tg threshold of 2.5 ng/ml or greater optimally predicted future recurrence with sensitivity, specificity, and negative and positive predictive values of 80, 97, 95, and 84%, respectively.
  
  
  CONCLUSIONS
  The prevalence of postablation thyroid cancer recurrence is predicted by the rhTSH-Tg response with an optimal Tg threshold of 2.5 ng/ml. Still, recurrent disease occurs in some patients with an initial rhTSH-Tg of 0.5 ng/ml or less.
authors.affiliation: Department of Internal Medicine, The Ohio State University Medical Center, 446 McCampbell Hall, 1581 Dodd Drive, Columbus, Ohio 43210, USA. richard.kloos@osumc.edu
authors.forename: Richard T
authors.initials: RT
authors.lastname: Kloos
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001323:Autoantibodies / Q000097:blood; D002648:Child; D005260:Female; D006801:Humans; D008197:Lymph Node Excision; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000097:blood / Q000175:diagnosis / Q000473:pathology / Q000517:prevention & control / Q000601:surgery*; D009367:Neoplasm Staging; D011994:Recombinant Proteins / Q000097:blood; D013954:Thyroglobulin / Q000097:blood* / Q000172:deficiency / Q000276:immunology; D013964:Thyroid Neoplasms / Q000097:blood / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery*; D013965:Thyroidectomy; D013972:Thyrotropin / Q000097:blood; D014463:Ultrasonography
chemical_list: D001323:Autoantibodies; D011994:Recombinant Proteins; D013972:Thyrotropin; D013954:Thyroglobulin