Clinical impact of detectable antithyroglobulin antibodies below the reference limit (borderline) in patients with papillary thyroid carcinoma with negative serum thyroglobulin and neck ultrasonography after ablation: a prospective study.

Clinical impact of detectable antithyroglobulin antibodies below the reference limit (borderline) in patients with papillary thyroid carcinoma with negative serum thyroglobulin and neck ultrasonography after ablation: a prospective study.

Thyroid. 2018 Jan 12;:

Authors: Carvalho M, Rosario PW, Mourão GF, Oliveira LFF, Calsolari MR

Abstract
BACKGROUND: Interference of antithyroglobulin antibodies (TgAb) with serum thyroglobulin (Tg) can occur even at detectable TgAb concentrations below the reference limit (borderline TgAb). Thus, borderline TgAb is considered positive TgAb in patients with thyroid cancer. This prospective study evaluated patients with papillary thyroid carcinoma with negative Tg and neck ultrasonography (US) after initial therapy and compared tumor persistence/recurrence and long-term Tg and TgAb behavior in those with borderline versus undetectable TgAb.
METHODS: We evaluated 576 patients divided into two groups: group A with undetectable TgAb (n = 420), and group B with borderline TgAb (n = 156).
RESULTS: Groups A and B were similar in terms of patient and tumor characteristics. The time of follow-up ranged from 24 to 120 months. During follow-up, 11 patients of group A (2.6%) and 5 of group B (3.2%) presented recurrence (p = 0.77). In group A, recurrences occurred in 9/390 patients who continued to have undetectable TgAb and in 1/9 who progressed to borderline TgAb. In group B, recurrences were detected in 1/84 patients who progressed to undetectable TgAb, in 1/45 who still had borderline TgAb, and in 3/12 who developed elevated TgAb. In the presence of negative Tg, recurrences were detected in 2/486 patients with undetectable TgAb, in 0/67 with borderline TgAb, and in 3/12 with elevated TgAb. We also analyzed the results of post-therapy whole-body scanning (RxWBS) of 216 patients with Tg ≤ 0.2 ng/ml and negative US at the time of ablation. In low-risk patients, none of the 40 patients with borderline TgAb and none of the 94 with undetectable TgAb exhibited ectopic uptake on RxWBS. In intermediate-risk patients, lymph node metastases were detected by RxWBS in 1/25 with borderline TgAb (4%) and in 2/57 with undetectable TgAb (3.5%).
CONCLUSIONS: Our results suggest that, in the patients with negative Tg and US after thyroidectomy, those with borderline TgAb are at no greater risk of tumor persistence or recurrence than those with undetectable TgAb. When negative Tg persists, recurrence should be suspected in the case of TgAb elevation (above the reference limit).

PMID: 29325506 [PubMed - as supplied by publisher]

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