Value of the Postablative Thyroglobulin Measurements for Assessment of Disease-Free Status in Patients with Differentiated Thyroid Cancer.

Aim: The aim of the study is to evaluate the value of thyroid-stimulating hormone (TSH)-stimulated thyroglobulin (sTg) measurements by the end of the 1-year postablation in differentiated thyroid cancer (DTC) patients with biochemical non complete response (indeterminate and incomplete response).

Patients And Methods: One hundred patients with DTC underwent near-total thyroidectomy and radioactive remnant ablation by iodine-131 (I) with regular follow-up every 6 months during the first 2 years and at 6-12-month intervals thereafter by I whole-body scan (WBS), neck ultrasound, and sTg measurement in the hypothyroid state (TSH >30 mU/L). Patients were divided according to the imaging findings and sTg level into three groups: excellent response (ER) - no evidence of disease by imaging and sTg <1 ng/mL, indeterminate or acceptable response (AR) - nonspecific findings on imaging studies and sTg < 10 ng/mL, and incomplete response (IR) - patients with incomplete structural and/or incomplete biochemical response (sTg > 10 ng/mL).

Results: The follow-up at 6-month postablation showed ER in 3 (3%) patients, AR in 29 (29%) patients, and IR in 68 (68%) patients. The second follow-up at 9-12-month postablation showed dramatic biochemical response with ER, indeterminate, and IR in 50 (50%), 34 (34%), and 16 (16%) patients, respectively, and 14 (14%) patient had structural recurrence. This change is highly statistically significant ( = 0.00). In the last follow-up (ranges from 3 to 10 years), 53 (55.8%) patients achieved ER, 42 (44.2%) AR and no patient with non complete response. The change in patients with IR between the second and the last follow-up is also statistically significant ( = 0.001).

Conclusion: sTg measurement by the end of the 1 year is more reliable in the follow-up of patients with DTC and biochemical non complete response and considered significant predictor of disease-free status. Patients with biochemical IR still have the chance to achieve ER or AR by the passage of time without additional therapies.