Low thyroglobulin concentrations after thyroidectomy increase the prognostic value of undetectable thyroglobulin levels on levo-thyroxine suppressive treatment in low-risk differentiated thyroid cancer.
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.
Piccardo
A
A
Department of Nuclear Medicine, Galliera Hospital, Mura delle Cappuccine 14, Genoa, Italy. arnoldo.piccardo@galliera.it
Arecco
F
F
Morbelli
S
S
Bianchi
P
P
Barbera
F
F
Finessi
M
M
Corvisieri
S
S
Pestarino
E
E
Foppiani
L
L
Villavecchia
G
G
Cabria
M
M
Orlandi
F
F
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
D007457:Iodine Radioisotopes; D011994:Recombinant Proteins; D013972:Thyrotropin; D013954:Thyroglobulin; D013974:Thyroxine