Preablative Stimulated Thyroglobulin Correlates to New Therapy Response System in Differentiated Thyroid Cancer.

CONTEXT

Studies suggested a potential value of preablative stimulated thyroglobulin (ps-Tg) on predicting the recurrent and persistent diseases of differentiated thyroid cancer, whereas its correlations with therapeutic response remain uncertain.

OBJECTIVE

To establish the correlation between ps-Tg and therapeutic response proposed in 2015 American Thyroid Association guidelines, and calculate a cutoff ps-Tg threshold for predicting a poor response.

DESIGN/SETTING: Patients who underwent total thyroidectomy and radioactive iodine therapy in a university hospital participated in this retrospective study.

PATIENTS

Totally, 452 patients with differentiated thyroid cancer were followed for a median of 38 months and were divided into three groups in terms of ps-Tg level: group 1, less than 1 ng/ml (n = 82); group 2, 1-10 ng/ml (n = 173); and group 3, at least 10 ng/ml (n = 197).

MAIN OUTCOME MEASURE

Clinical outcomes were assessed based on response to therapy restaging system, dividing responses into excellent, indeterminate, biomedical incomplete, and structural incomplete (SIR).

RESULTS

Therapeutic responses could be obviously distinguished by different ps-Tg strata. SIR was identified in none of group 1, 1.73% of group 2, and 42.74% of group 3, respectively (χ(2) = 123.037, P < .001). A cutoff value of ps-Tg at 26.75 ng/ml was obtained by receiver operating characteristic curve for differentiating SIR from either excellent, indeterminate, or biomedical incomplete responses. The area under curve was 0.947 and negative predictive value was 96.99%. Ps-Tg was an independent predictive variable of SIR (odds ratio, 42.312; P < .001).

CONCLUSIONS

Ps-Tg has a great performance in predicting therapeutic response and providing incremental value for decision making of radioactive iodine therapy, especially for patients with high ps-Tg level.