Prognostic value of the preoperative and early trends in postoperative serum thyroglobulin antibody levels among patients with papillary thyroid carcinoma and concomitant Hashimoto's thyroiditis.

Background: Thyroglobulin antibody(TgAb) was generally used as a prognostic marker of papillary thyroid cancer(PTC) only after total thyroidectomy, but its value in PTC patients with concomitant Hashimoto's thyroiditis(HT) is unclear. We aimed to assess the prognostic significance of the serum TgAb in these patients.

Methods: This retrospective cohort study included PTC patients and pathologically proven HT from 2007-2016. The Cox proportional hazards model with restricted cubic spline was used to analyze the association between TgAb and structural recurrence, and then survival analysis was performed.

Results: Of 839 patients enrolled, 48 recurrences were identified during a median follow-up of 64 months. Macrocarcinoma and lymph node metastasis were significantly associated with higher TgAb (P = 0.006, 0.002), but no significant difference was found for any other characteristics. An increasing preoperative TgAb level up to 2000 IU/ml was associated with shorter recurrence-free survival(RFS) (P < 0.001), and the 5-year RFS rates in patients with TgAb ≤400, 400-800 and >800 IU/ml were 97.3%, 93.2% and 85.8%, respectively (P < 0.05). The difference was found even after adjusting for potential risk factors (P < 0.001). Of 337 PTC patients who were treated with lobectomy and had available TgAb data at the first year after surgery, a significant decrease (≥50%) in postoperative TgAb was achieved in 41.8% patients, who had a favorable prognosis compared with others (5-year RFS rate 98.5% vs. 92.0%, P = 0.008).

Conclusions: The preoperative serum TgAb seem to effectively stratify PTC patients with concomitant HT who had high risk for recurrence, and the early postoperative trends of TgAb was a good prognostic marker for these patients who treated with lobectomy.