Prognostic value of an increase in the serum thyroglobulin level at the time of the first ablative radioiodine treatment in patients with differentiated thyroid cancer.
OBJECTIVE
The aim of this study was to assess the prognostic factors for treatment efficacy, and in particular the increase in serum thyroglobulin (Tg) level at the time of the first ablative radioiodine treatment, in patients with differentiated thyroid carcinoma (DTC).


METHODS
A retrospective chart review was performed on 407 patients treated for DTC by total thyroidectomy and (131)I ablation between 1995 and 2002, and examined 5-12 months later with diagnostic (131)I whole-body scan and serum Tg measurement after thyroid hormone treatment withdrawal. At the time of the ablative radioiodine treatment, serum Tg level was determined just before (131)I administration (TgD0) and 5 days later (TgD5); Tg variation was expressed as the ratio TgD5/TgD0. At the first post-ablation follow-up examination, unsuccessful ablation was defined by a Tg level > or =2 ng/ml and/or abnormal (131)I uptake.


RESULTS
Ablation was unsuccessful in 51 patients. Univariate analysis showed high TgD0 level, low TgD5/TgD0 ratio extrathyroidal invasion, (131)I uptake in the neck (excluding the thyroid bed) during the ablative treatment and distant metastases to be significantly associated with unsuccessful ablation. On logistic multivariate analysis, TgD0 level <5 ng/ml and TgD5/TgD0 ratio > or =20 were independently associated with successful ablation. A receiver operating characteristic curve analysis determined that a TgD5/TgD0 ratio greater than 20 had a 97% positive predictive value for successful ablation. When both TgD0 and TgD5/TgD0 ratio were considered, that is, TgD0 <5 ng/ml or TgD0 > or =5 ng/ml but TgD5/TgD0 ratio >20, ablation was unsuccessful in only 12/301 patients.


CONCLUSIONS
Our data show that the TgD5/TgD0 ratio may be used as a new prognostic indicator of (131)I treatment efficacy in patients with DTC.
Bernier
Marie-Odile
MO
Department of Nuclear Medicine, Centre Paul Papin, Angers 49033, France.
Morel
Olivier
O
Rodien
Patrice
P
Muratet
Jean-Pierre
JP
Giraud
Philippe
P
Rohmer
Vincent
V
Jeanguillaume
Christian
C
Bigorgne
Jean-Claude
JC
Jallet
Pierre
P
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000097:blood*; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D013964:Thyroid Neoplasms / Q000097:blood* / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D016896:Treatment Outcome
D014408:Biomarkers, Tumor; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals