Impact of co-existent thyroiditis on clinical outcome in papillary thyroid carcinoma with high preoperative serum antithyroglobulin antibody: a retrospective cohort study.

Objectives The aim of this study was to investigate the impact of co-existent chronic lymphocytic thyroiditis (CLT) on changes in serum antithyroglobulin antibody (TgAb) and clinical outcome in papillary thyroid carcinoma (PTC) patients with high preoperative serum TgAb. Design A retrospective cohort study. Setting University teaching hospital. Participants Thirty-seven PTC patients with high preoperative serum TgAb level (≥100 U/mL) were evaluated. All patients underwent total thyroidectomy followed by high-dose I-131 ablation. Main outcome measures Per cent changes of TgAb between pre-treatment and post-treatment, and disease-free survival were calculated. Results Twenty-two patients (59.5%) had co-existent CLT, and seven had residual/recurrent tumours. There was a higher proportion of females among the patients with CLT compared to those without CLT (95.5% versus 66.7%; P = 0.0306). There were trends towards more aggressive pathologies, such as tumour size, extrathyroidal extension, surgical margin and lymph node stage, in PTC without CLT than in that with co-existent CLT. Pre-treatment and post-treatment TgAb were all higher in PTC with co-existent CLT. But, per cent changes of TgAb between pre-treatment and post-treatment were no significant difference between PTC with and without CLT (P < 0.05). Patients with co-existent CLT showed a significantly lower residual/recurrent tumour rate than those without CLT (4.5% versus 40%; P = 0.0113). Conclusion Residual/recurrent tumour rate was lower in PTC patients with co-existent CLT than in those without CLT.