Follow-up of patients with thyroid cancer and antithyroglobulin antibodies: a review for clinicians.

Antithyroglobulin antibodies (TgAb) are present in up to 25% of patients with differentiated thyroid carcinoma on initial postoperative assessment. Detectable concentrations of TgAb even below the manufacturer's cut-off can interfere with serum thyroglobulin (Tg) determination. When Tg is quantified using an immunometric assay (IMA) (hereafter referred to as Tg-IMA), this interference results in underestimated values of Tg. Although promising, more clinical trials evaluating the capacity of liquid chromatography/tandem mass spectrometry and of new assays to detect elevated Tg in patients with TgAb and structural disease are necessary, particularly when Tg is undetectable by a second-generation IMA (Tg-2GIMA). Neck ultrasonography (US) should be performed in patients submitted to total thyroidectomy and with negative Tg-IMA but with detectable TgAb more than 6 months after initial therapy. In patients treated with 131I, comparison of TgAb concentrations obtained before this treatment is useful to estimate the risk of disease and to guide the investigation. If initial assessment does not reveal any persistent tumor, the repetition of US is recommended while TgAb persist. Significant elevation of TgAb requires extended investigation. On the other hand, patients with negative Tg-IMA and US without abnormalities who exhibit a reduction > 50% in TgAb generally do not require investigation. Although TgAb can interfere with Tg, the management and follow-up of patients submitted to total thyroidectomy with borderline TgAb can probably be the same as those recommended for patients without TgAb if Tg-2GIMA and US indicate an excellent response to therapy. Currently, the presence/absence or the trend of TgAb levels cannot be considered in the follow-up of patients submitted to lobectomy.

Role of adjuvant therapy with radioactive iodine in patients with elevated serum thyroglobulin after neck reoperation due to recurrent papillary thyroid cancer: a monoinstitutional comparative study.

BACKGROUND: Most patients with papillary thyroid cancer (PTC) and lymph node metastases (LNM) undergoing reoperation do not show apparent disease after this procedure, but serum thyroglobulin (Tg) continues to be elevated in part of them. This study evaluated adjuvant therapy with 131I in these patients. METHODS: Patients with PTC and LNM diagnosed after initial therapy were selected. Patients undergoing reoperation and those without apparent disease after this procedure, but with nonstimulated Tg ≥1 ng/ml 6 months after reoperation, were included. The first 25 patients were submitted to therapy with 131I (groups A) and the subsequent 30 patients did not receive this therapy (group B). RESULTS: Groups A and B were similar. During further follow-up, 21 patients developed structural disease and 34 continued without detectable disease (eight achieved complete remission). The outcomes were similar in groups A and B. Patients with Tg reduction >50% after reoperation tended to have a lower risk of recurrence (22.7 versus 48.5%), notably distant metastases (0 versus 15.1%), and were more likely to achieve complete remission (28 versus 3%). Patients with LNM FDG-positive had a higher risk of recurrence (54.5 versus 11.7%) and were less likely to achieve complete remission (3 versus 29.4%) after reoperation. CONCLUSION: Our results suggest that therapy with 131I apparently does not prevent recurrences among patients who continue to have elevated Tg after neck reoperation. Further studies involving these patients are necessary, especially those who are at high risk of recurrence.

Is Stimulated Thyroglobulin Necessary after Ablation in All Patients with Papillary Thyroid Carcinoma and Basal Thyroglobulin Detectable by a Second-Generation Assay?

Objective. To evaluate the percentage of elevated stimulated thyroglobulin (sTg) and persistent or recurrent disease (PRD) in patients with detectable basal Tg < 0.3 ng/mL. Methods. The sample consisted of 130 patients with papillary thyroid carcinoma (PTC) who were at low risk of PRD and who had neck ultrasound (US) without abnormalities, negative anti-Tg antibodies (TgAb), and detectable basal Tg < 0.3 ng/mL about 6 months after ablation. Results. sTg was <1 ng/mL in 88 patients (67.7%), between 1 and 2 ng/mL in 26 (20%), and ≥2 ng/mL in 16 (12.3%). Imaging methods revealed the absence of tumors in 16 patients with elevated sTg. During follow-up, Tg increased to 0.58 ng/mL in one patient and lymph node metastases were detected. Sixty-nine patients continued to have detectable Tg < 0.3 ng/mL and US revealed recurrence in only one patient. Sixty patients progressed to persistently undetectable Tg without apparent disease on US. Conclusions. In low-risk patients with PTC who have detectable basal Tg < 0.3 ng/mL after ablation, negative TgAb, and US, persistent disease is rare and eventual recurrences can be detected by basal Tg elevation and/or subsequent US assessments, with follow-up without sTg being an "alternative" to Tg stimulation.