Successful thyroid tissue ablation as defined by a negative whole-body scan or an undetectable thyroglobulin: a comparative study.
BACKGROUND
Successful thyroid tissue ablation of patients with well-differentiated thyroid cancer can be defined by a negative whole-body scan (WBS) and/or an undetectable thyroglobulin (Tg). Variables associated with success are poorly understood. Tg measurement, although more sensitive than WBS, has not been firmly established as the sole monitoring method. In a previous study, we retrospectively evaluated the variables associated with scintigraphic success. Ablation dose (AD) was the only variable associated with success (odds ratio (OR): 1.96 per 1.85 GBq increment; 95% confidence interval (CI)=1.11-3.46).


OBJECTIVE
(1) To determine if the variables associated with success are the same using Tg. (2) To determine whether Tg measurement can become the sole method for assessing ablation success.


METHODS
We performed the analysis using a Tg level <2 ng.ml-1 as a criterion for completed ablation. Data were available from 109 patients.


RESULTS
Univariate analysis showed an effect of stage (OR=0.05; 95% CI=0.01-0.23) and female sex (OR=2.8; 95% CI=1.14-6.89). Multivariate analysis demonstrated only stage to be a significant predictor of success. Ablation was successful by both methods in 62/109 patients and it failed by both in 10/109. There were 21 WBS- Tg+ and 16 WBS+ Tg- patients.


CONCLUSIONS
Investigation of the variables associated with successful ablation yields different results depending on the definition of success. There was a significant incidence of WBS+ Tg- cases after initial ablation. Until it is firmly established that such patients have a benign course both monitoring methods should be used.
Karam
Maroun
M
Division of Nuclear Medicine, Albany Medical College, Albany, NY 12208, USA. karamm@mail.amc.edu
Feustel
Paul J
PJ
Postal
Eric S
ES
Cheema
Ayesha
A
Goldfarb
C Richard
CR
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000097:blood / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000517:prevention & control*; D011379:Prognosis; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D013954:Thyroglobulin / Q000097:blood*; D013964:Thyroid Neoplasms / Q000097:blood / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000628:therapy*; D013965:Thyroidectomy / Q000379:methods*; D016896:Treatment Outcome; D014915:Whole-Body Counting / Q000379:methods
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D013954:Thyroglobulin