Changes in serum thyroglobulin antibody levels as a dynamic prognostic factor for early-phase recurrence of thyroglobulin antibody-positive papillary thyroid carcinoma after total thyroidectomy.

We demonstrated previously that dynamic prognostic markers such as the thyroglobulin (Tg)-doubling time in thyroglobulin antibody (TgAb)-negative papillary thyroid carcinoma (PTC) and changes in pre- and postoperative TgAb levels in TgAb-positive PTC patients more keenly reflect patients' prognosis than conventional static prognostic factors. Here we investigated periodic changes in TgAb levels in 513 TgAb-positive PTC patients who underwent total thyroidectomy. The TgAb levels at 1 year after surgery decreased to <50% of the preoperative values in 407 (79%) patients, and the remaining 106 (21%) patients showed no decrease in TgAb. In 426 patients, TgAb was also measured more than 1 year after surgery. Compared with their TgAb levels 1 year after surgery, 59 patients (14%) showed an increase in TgAb levels of >20% during the follow-up. The postoperative Tg levels at 1 year after surgery remained positive in 44 (9%) patients despite their TgAb positivity. To date (median follow-up period 35 months), 12 of the 426 patients (3%) showed PTC recurrence, and 11 of these patients showed either or both a TgAb elevation later than 1 year after surgery and postoperative Tg positivity. Although further studies with longer follow-ups are necessary, we can conclude that changes in postoperative TgAb levels may be usable as a surrogate tumor marker for TgAb-positive PTC patients after total thyroidectomy.