title: Low thyroglobulin concentrations after thyroidectomy increase the prognostic value of undetectable thyroglobulin levels on levo-thyroxine suppressive treatment in low-risk differentiated thyroid cancer.
abstract: METHODS
  Recombinant human TSH-stimulated thyroglobulin (Tg) levels (rhTSH-Tg) are sufficient for early follow-up of low-risk differentiated thyroid cancer (DTC) patients after thyroidectomy and radioiodine (131I) remnant ablation (RAI). Serum Tg levels at the time of remnant ablation (ablation-Tg) is thought to be related with rhTSH-Tg and may be predictive of recurrent disease. During long-term follow-up, Tg levels on levo-T4 (L-T4) suppressive treatment (suppressive-Tg) is sufficiently sensitive to avoid further evaluations in patients with undetectable rhTSH-Tg. The aim of our study was to verify whether, in a subgroup of low-risk DTC patients, the association of low ablation-Tg levels (<10 microg/l) with undetectable suppressive-Tg concentrations has a sufficient negative predictive value (NPV) for recurrence of disease, leading to avoid rhTSH testing.
  
  
  METHODS
  We enrolled 169 low-risk DTC patients treated by thyroidectomy + RAI and undetectable suppressive-Tg at 12-month followup. In all patients, we retrospectively evaluated ablation-Tg and rhTSH-Tg. For all patients, 2-yr follow-up was available.
  
  
  RESULTS
  Based on rhTSH-Tg>2 microg/l, relapsing disease was histologically proven in 2 patients. rhTSH-Tg levels between 0.6-2.0 microg/l, with no evidence of disease, was observed in 10 patients (6%). One hundred and fifty-seven patients showed undetectable rhTSH-Tg. The NPV of undetectable suppressive- Tg was 92.8%. The ablation-Tg level was <10 microg/l in 140 patients. In this group, the NPV of undetectable suppressive- Tg was 100%.
  
  
  CONCLUSIONS
  Our data indicate that undetectable suppressive-Tg value, combined with ablation- Tg levels <10 microg/l, may avoid a significant number of high-cost rhTSH-Tg test.
authors.affiliation: Department of Nuclear Medicine, Galliera Hospital, Mura delle Cappuccine 14, Genoa, Italy. arnoldo.piccardo@galliera.it
authors.forename: A
authors.initials: A
authors.lastname: Piccardo
authors.forename: F
authors.initials: F
authors.lastname: Arecco
authors.forename: S
authors.initials: S
authors.lastname: Morbelli
authors.forename: P
authors.initials: P
authors.lastname: Bianchi
authors.forename: F
authors.initials: F
authors.lastname: Barbera
authors.forename: M
authors.initials: M
authors.lastname: Finessi
authors.forename: S
authors.initials: S
authors.lastname: Corvisieri
authors.forename: E
authors.initials: E
authors.lastname: Pestarino
authors.forename: L
authors.initials: L
authors.lastname: Foppiani
authors.forename: G
authors.initials: G
authors.lastname: Villavecchia
authors.forename: M
authors.initials: M
authors.lastname: Cabria
authors.forename: F
authors.initials: F
authors.lastname: Orlandi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis; D011379:Prognosis; D011994:Recombinant Proteins; D013954:Thyroglobulin / Q000097:blood*; D013964:Thyroid Neoplasms / Q000532:radiotherapy / Q000601:surgery; D013965:Thyroidectomy; D013972:Thyrotropin; D013974:Thyroxine / Q000627:therapeutic use
chemical_list: D007457:Iodine Radioisotopes; D011994:Recombinant Proteins; D013972:Thyrotropin; D013954:Thyroglobulin; D013974:Thyroxine