Long-Term Follow-Up in Patients with Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features (NIFTP) Without a Suspicion of Persistent Disease in Postoperative Assessment

The objective was to determine whether negative assessment after surgery is a predictor of no relevant change of the results in subsequent evaluations in patients with noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). Six months after surgery, "absence of persistent disease" was defined when concentration of thyroglobulin (Tg) is ≤2 ng/ml in patients undergoing total thyroidectomy and ≤10 ng/ml in those undergoing lobectomy, in the absence of antithyroglobulin antibodies (TgAb), and neck ultrasonography (US) without abnormalities. One hundred thirteen patients met the definition of "absence of persistent disease". The patients were followed up for 18-150 months. None of the patients developed structural disease. In the 56 patients undergoing total thyroidectomy, 380 Tg measurements were obtained and an increase in concentrations was not observed in any of them. During the same period, 332 US scans were performed and a suspicious lymph node was detected on only one occasion, but was not metastatic on fine needle aspiration (FNA). In the 57 patients undergoing lobectomy, 382 Tg measurements were obtained and increases or persistent concentrations>10 ng/ml were not observed in any patient. During the same period, 376 US scans were performed and nodules with an indication for FNA were detected in 4 patients, but malignancy was not confirmed in any of them. Finally, TgAb were not elevated in any of the 762 measurements obtained from the 113 patients. After complete resection of NIFTP, negative postoperative assessment can be used to exclude the need for long-term repetition of these tests.

Clinical Impact of Detectable Antithyroglobulin Antibodies Below the Reference Limit (Borderline) in Patients with Papillary Thyroid Carcinoma with Undetectable Serum Thyroglobulin and Normal Neck Ultrasonography After Ablation: A Prospective Study

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 as TgAb positivity in patients with thyroid cancer. This prospective study evaluated patients with papillary thyroid carcinoma with undetectable Tg and normal neck ultrasonography (US) after total thyroidectomy and ablation with ¹³¹I, and compared tumor persistence/recurrence and long-term Tg and TgAb behavior in those with borderline versus undetectable TgAb.

METHODS

A total of 576 patients were evaluated, 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 (2.6%) patients in group A and 5 (3.2%) in group B developed a recurrence (p = 0.77). In group A, recurrences occurred in 9/390 patients who continued to have undetectable TgAb and in 1/9 patients who progressed to borderline TgAb. In group B, recurrences were detected in 1/84 patients who progressed to have undetectable TgAb, in 1/45 who still had borderline TgAb, and in 3/12 who developed elevated TgAb. In the presence of Tg levels <0.2 ng/mL, recurrences were detected in 2/486 patients with undetectable TgAb, in 0/67 with borderline TgAb, and in 3/12 with elevated TgAb. The results of post-therapy whole-body scanning (RxWBS) of 216 patients with Tg ≤0.2 ng/mL and normal US at the time of ablation were also analyzed. 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 (4%) with borderline TgAb and in 2/57 (3.5%) with undetectable TgAb.

CONCLUSIONS

The results suggest that among low- or intermediate-risk patients with undetectable Tg and normal US after thyroidectomy, those with borderline TgAb are at no greater risk of tumor persistence or recurrence than those with undetectable TgAb. When undetectable Tg levels persist, recurrence should be suspected in the case of a TgAb elevation above the reference limit.