Dual Role of AITD in TgAb-Positive PTC: Delayed Antibody Clearance with Enhanced RAIT Response

Elevated thyroglobulin antibody (TgAb) levels in postoperative management of papillary thyroid carcinoma (PTC) are often attributed to tumor recurrence, while the potential impact of autoimmune thyroid disease (AITD) is overlooked. This study aims to clarify the comprehensive effects of AITD on baseline TgAb levels, antibody normalization kinetics, pre-RAIT persistent structural disease risk, and radioactive iodine therapy (RAIT) efficacy in PTC patients.

A retrospective cohort of 287 TgAb-positive (≥115 IU/mL) PTC patients who underwent total thyroidectomy and received RAIT with ≥6 months follow-up was enrolled. Based on postoperative pathology and thyroid peroxidase antibody (TPOAb) status, patients were divided into Group A0 (non-AITD, n=70) and Group A1 (AITD-concurrent, n=217). Clinicopathological characteristics, RAIT response, and TgAb normalization were compared.

Among TgAb-positive PTC patients, 75.6% had concurrent AITD. Group A1 exhibited higher pre-RAIT TgAb levels (740.0[450.0-1050.0] vs 520.5[300.0-800.0]IU/mL, Z = -2.155, p = 0.031) and pre-RAIT persistent structural disease rates (38.7% vs 25.7%, p = 0.048) than Group A0. Although the total RAIT dose and final therapeutic response were comparable between groups, patients in Group A1 received fewer RAIT cycles (median: 1 vs 2, p = 0.042). Notably, TgAb normalization time was significantly prolonged in Group A1 (median: 40.81 vs 33.55 months, Log-rank p = 0.043), with Cox regression confirming slower antibody clearance in AITD patients (HR = 0.667, 95% CI: 0.452-0.983).

Concurrent AITD is associated with elevated TgAb, delayed antibody clearance, and increased pre-RAIT persistent structural disease risk, yet does not compromise RAIT efficacy. This highlights the dual role of AITD in PTC prognosis.