Investigating Antithyroglobulin Antibody As a Prognostic Marker for Differentiated Thyroid Cancer: A Meta-Analysis and Systematic Review

Background: Serum thyroglobulin (Tg) is used in the follow-up of patients with differentiated thyroid cancers (DTC), but the presence of antithyroglobulin antibodies (TgAbs) makes Tg measurements unreliable. TgAb decline after total thyroidectomy and persistent/increasing levels may indicate cancer persistence/recurrence. Hence, we aimed to determine whether TgAb might be a reliable prognostic marker for DTC. Methods: We conducted a meta-analysis and systematic review. A comprehensive literature search was performed to identify studies of patients with DTC with known TgAb status and prognostic outcomes in five databases (Medline, Embase, PubMed, Google Scholar, and Scopus). We used a random-effects model to calculate pooled odds ratios (ORs) and 95% confidence intervals (CIs) for TgAb status and its association with DTC prognosis. Results: After analysis of 34 studies, we found that TgAb+ patients have a higher risk of lymph node metastasis (OR = 1.18 [CI 1.47-2.25]) and cancer persistence/recurrence (OR = 2.78 [CI 1.55-4.98]) than TgAb- patients. However, no significant differences in mean/median tumor size, risk of extrathyroidal extension, tumor multifocality, and cancer mortality were found between the two groups. In a comparison of TgAb trends, patients with persistent/increasing TgAb levels were found to have a higher risk of cancer persistence/recurrence (OR = 9.90 [CI 4.36-22.50]) and cancer mortality (OR = 15.18 [CI 2.99-77]) than patients with decreasing TgAb levels. Conclusions: TgAb positivity and persistent/increasing trends were associated with compromised DTC prognosis. These results suggest that TgAb may be used as a prognostic marker in the follow-up of patients with DTC.

Diagnostic Performance of 18F-FDG PET/CT in Papillary Thyroid Carcinoma with Negative 131I-WBS at first Postablation, Negative Tg and Progressively Increased TgAb Level

Differentiated thyroid cancer (DTC) patients with negative serum thyroglobulin (Tg), negative ¹³¹I whole–body scintigraphy (¹³¹I-WBS) at first post-ablation and progressively increased TgAb level are a relatively rare entity in the follow-up after total thyroidectomy and radioactive iodine therapy. The value of ¹⁸F-FDG PET/CT in detecting the recurrence of disease in these patients has only been reported in a small case series. The goal of this study was to investigate the diagnostic accuracy of ¹⁸F-FDG PET/CT in detecting recurrent disease in these specific PTC patients and to identify risk factors for patients with positive ¹⁸F-FDG PET/CT results. Eighty-two PTC patients who had ¹⁸F-FDG PET/CT scans with negative Tg, negative ¹³¹I-WBS at first post-ablation and progressively increased TgAb levels were included. We found that the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of ¹⁸F-FDG PET/CT in this patient group were determined as 84%, 72%, 92%, 57% and 82%, respectively. ¹⁸F-FDG PET/CT scan had a good diagnostic performance and should be performed routinely in PTC patients with negative Tg, negative ¹³¹I-WBS at first postablation and progressively increased TgAb level, especially when span for progressively increased TgAb level ≥ 3 years and/or progressively increased TgAb value up to 150 IU/mL.

Age and body composition influence TSH concentrations after administration of rhTSH

AIM

Previous studies listed body surface area (BSA), lean body mass (LBM), and age as modifying factors on the TSH concentrations after administration of recombinant human thyrotropin (rhTSH). The purpose of this study was to identify the main modifying factors on serum TSH levels and to compare the stimulation via single rhTSH injection after a short thyroid hormone withdrawal (THW) with that of the standard stimulating protocol.

PATIENTS, METHODS

106 patients with differentiated thyroid cancer (DTC) undergoing radioiodine therapy (RIT) after rhTSH administration were obtained through chart review. Two groups were evaluated: Group I was treated with a single rhTSH administration after two weeks of T3 therapy followed by one week of THW. Group II was stimulated according to the international standard protocol via rhTSH injections for two consecutive days. Serum TSH concentrations were documented prior to rhTSH administration (day 1 TSH), one day after (day 3 TSH) and 3-6 days after (mean 4.2 days, day 6 TSH) the last rhTSH injection. The following data was collected: age, gender, weight, height, BMI, LBM, BSA, residual thyroid tissue, CRP, creatinine, GFR, liver enzymes, alkaline phosphatase, cholesterol, and triglycerides.

RESULTS

Group I: Age combined with anthropometric factors like BMI (TSH increase and day 6 TSH), BSA (TSH decrease), and gender (day 6 TSH) are the main modifying factors on serum TSH concentrations after rhTSH administration. Group II: Age and lean body mass (LBM) showed a significant impact on day 3 TSH, TSH increase (day 3-day 1), and TSH decrease (day 6-day 3). Day 6 TSH was found to be influenced by GFR (group II).

CONCLUSION

Age and anthropometric parameters have significant independent influence on TSH concentrations after rhTSH injection in both groups. Anthropometric parameters (BSA, LBM) and demographic parameters (female gender) show strong influence on TSH concentrations. Further research should be conducted to examine the influence of body compartments on TSH levels through measuring total body water.

The role of FDG-PET/CT in differentiated thyroid cancer patients with negative iodine-131 whole-body scan and elevated anti-Tg level

AIM

In the follow-up of differentiated thyroid cancer (DTC) after a successful total-near total thyroidectomy and I-131 ablation therapy, anti-thyroglobulin antibodies (anti-Tg) may be persistently or progressively increased in the patients with an undetectable serum thyroglobulin (Tg) level. In these cases, further investigation was performed to search for recurrence/metastases. The aim of our study was clarifying the role of FDG-PET/CT in detecting recurrence/metastasis in patients with DTC with negative serum Tg and elevated anti-Tg level.

MATERIALS AND METHODS

A total of 40 patients (32 female, 8 male; mean age: 43.15 years (22-65); mean age at diagnosis: 39.08 (16-64)) with DTC who had undetectable serum Tg and elevated anti-Tg level after a successful initial therapy were included in the study. All of the patients had serum anti-Tg of >40 IU/ml and underwent FDG-PET/CT to search for recurrence/metastasis.

RESULTS

Twenty patients (50 %) had recurrence/metastasis on FDG-PET/CT while the other 20 had no pathologic findings. Of the 20 patients who had positive FDG-PET/CT, 12 had a histopathological final diagnosis of which 11 were true positive (TP) and 1 was false positive (FP). On the other hand, 16 of the 40 patients had a histopathological final diagnosis of which 11/16 had TP, 1/16 FP, 3/16 false negative (FN) and 1/16 true negative (TN) findings by PET/CT. The final diagnosis was made by clinical follow-up in the remaining 24 patients. Of these, 8 patients were PET positive, and in 1 (12.5 %) of 8 patients a decrease in serum anti-Tg level, in 2 (25 %) patients a saw-toothed pattern and in 5 (62.5 %) a progressive increase in the serum anti-Tg level were noted during the follow-up. Of the 16 of 24 patients who were diagnosed by clinical follow-up, in 8 a (50 %) decrease in serum anti-Tg level, in 6 (37.5 %) a saw-toothed pattern, and in 2 (12.5 %) a progressively increased anti-Tg level was seen. Of the 40 patients, 14 (35 %) had a diagnosis of recurrence/metastasis finally, with PET/CT detecting 11 (78.6 %) of them.

CONCLUSION

The value of a persistently or progressively increased serum anti-Tg level in the follow-up of DTC in the prediction of recurrence/metastasis is controversial. However, it is reported that FDG-PET can be useful in the detection of recurrence/metastasis. We conclude from the available data that PET/CT can be effectively used in the detection of recurrence/metastasis in the follow-up of patients with DTC and negative serum Tg and a persistently/progressively increased anti-Tg level. Besides, one half of the patients were FDG negative, meaning that further studies are needed to assess the prognostic-clinical value of PET negativity.