The relevance of thyroid autoimmunity to the prognosis of papillary thyroid carcinoma is still unsettled. We decided to investigate the impact of thyroid autoimmunity on the prognosis of papillary thyroid carcinoma and the handling of TgAbs. We evaluated the clinical course of a large group of patients according to the presence (PTC-LT) or absence (PTC) of lymphocytic thyroiditis at histology. We studied 194 consecutive patients with a diagnosis of PTC and treated them with total thyroidectomy plus ¹³¹I ablation between 2007 and 2009. Median follow-up (with 25th-75th percentiles) was 84.0 (56.4-118.0) months. The remission criteria were: basal Tg < 0.2 ng/mL (or stimulated Tg: < 1), TgAbs < 8 IU/mL (otherwise 'decreasing TgAb trend', a decline of ≥20% in sequential TgAb measurements) and unremarkable imaging. PTC-LT and PTC patients had comparable treatment.TgAbs were detectable in 72.5% of PTC-LT and 16.5% of PTC patients. Time to remission was longer in the detectable than in the undetectable TgAb cohort (28.5 vs· 7.5 months (median); HR: 0.54, CI: 0.35-0.83, P = 0.005). When comparing PTC-LT to PTC patients, the difference was maintained in the detectable TgAb (29.3 vs 13.0 months; HR: 0.38, CI: 0.18-0.80; P = 0.01) but not in the undetectable TgAb cohort (7.7 vs 7.3 months; HR: 0.90, CI: 0.55-1.47; P = 0.68). Using the decreasing TgAb trend, the influence of detectable TgAbs on time to remission was abolished. Thyroid autoimmunity does not influence the prognosis of papillary thyroid carcinoma. A decreasing TgAb trend seems an appropriate criterion to establish the remission of papillary thyroid carcinoma.
Keywords: differentiated thyroid carcinoma; lymphocytic thyroiditis; papillary thyroid carcinoma; thyroglobulin; thyroglobulin autoantibodies; thyroid autoimmunity.