Thyroglobulin Antibodies (TgAb) Titer Spontaneously Decrease Until The Negativization Or Stabilization In Most Of Cases Of Papillary Thyroid Microcarcinoma (mPTC) Treated With Total Thyroidectomy But Not Ablated With 131I

Background: Thyroglobulin antibodies (TgAb) are present in about 25% of patient affected by Differentiated Thyroid Cancer (DTC). In these patients, after total thyroidectomy and radioiodine ablation (RAI), TgAb trend becomes a “surrogate” marker to assess the persistent/recurrent disease. Little is known about the clinical significance of TgAb trend in patients not submitted to RAI (No-RAI), as in case of microcarcinomas (mPTC). The aim of our study was to verify the TgAb trend during the follow-up of No-RAI cases. Methods: Among all No-RAI mPTC patients (n=383) followed at our Department from 2005 to 2012, we selected pts who had at least 3 determi- nations of serum TgAb. The epidemiological, clinico-pathological and neck ultrasound data have been collected. Results: 107/383 (27.9%) pts were TgAb positive (≥ 8mU/L). At the first post-surgical evaluation (3-6 months), 35.5% (38/107) pts had TgAb 8≤20 mU/L, 23.4% (25/107) pts 21≤50 mU/L, 24.3% (26/107) pts 51≤100 mU/L and 16.8% (18/107) pts >100 mU/L. At the end of the follow up (mean 5.9 yrs; median 5.75 yrs), 62.6% (67/107) pts had TgAb ˂8 mU/L, 21.5% (23/107) pts 8≤20 U/ml, 9.3% (10/107) pts 21≤50 mU/L, 2.8% (3/107) pts 51≤100 and only 3.7% (4/107) had TgAb >100 mU/L [p<0.01]. In all but one case the titer of TgAb was increasing and neck US became positive for local thyroid disease. Neck US was negative for local a/o lymph nodes metastatic disease in all patients at every time of the follow up. Conclusions: 1) After 6 years of follow up, in the majority of cases the TgAb titer was decreasing and became negative in 62.6% pts; 2) The only case of increasing TgAb showed the reappearance of thyroid tissue at neck US during the follow up