Prognostic Value of Postoperative and Post-ablative Serum Thyroglobulin Levels in Patients with Differentiated Thyroid Cancer

Prognostic Value of Basal Serum Thyroglobulin Levels, but Not Basal Antithyroglobulin Antibody (TgAb) Levels, in Patients with Differentiated Thyroid Cancer

Objective: The prognostic values of serum thyroglobulin (Tg) and antithyroglobulin antibody (TgAb) levels, measured immediately before I-131remnant ablation in patients with differentiated thyroid cancer (DTC), have been advocated by some researchers; however, it had controversial outcomes. This study was carried out to examine this dilemma and to check the clinical significance of basal serum Tg and TgAb levels and postablation iodine 131whole body scan(WBS) findings in DTC patients.

Methods: In this retrospective study, the records of 500 patients with differentiated thyroid cancer, who had undergone treatment between 2003 and 2010, were assessed. Of those, 149 patients with results of basal serum thyroglobulin concentration and whole body scan using radioactive iodine were included. Age, sex, tumour histology, basal thyroglobulin (Tg), anti-thyroglobulin (TgAb) and TSH concentration, radioactive iodine doses in each hospitalization, numbers of hospitalization, and results of whole body scans were recorded. The relationship among basal Tg, TgAb, TSH, and whole body scan with hospitalization number and total radioactive iodine doses were assessed.

Results: A total of 149 patients, including 123 (83%) females and 26 (17%) males, with a mean age of 40±15 years, took part in the study. The mean (SD) basal Tg, TgAb, and TSH were 91.7±169.2 ng/mL (0.1-1000 ng/mL), 250±893 U/mL (0-9000 U/m L), and 64.8±61.5 µU/mL (30-689 U/mLµ), respectively. A total of 52 (34.9%) cases had TgAb levels greater than 100 U/mL. The mean basal Tg in patients who were admitted three or more times was significantly greater than that of patients with one hospitalization (p=0.026). In addition, the mean of Tg in patients who received 7.4 GBq radioactive iodine or less was significantly lower than the others (p=0.003). The mean of TgAb and TSH were not different between these groups. In the results of the whole body scans, patients with metastasis had higher frequency of hospitalization (p=0.010) and received higher radioactive iodine levels (p<0.001).

Conclusions: The findings of this study showed that, in differentiated thyroid cancer, lower basal serum Tg levels and absence of metastasis in radioiodine scan after ablation treatment were correlated with fewer hospitalizations and lower doses of radioactive iodine. Basal TgAb and TSH had no relation. Therefore, it seems that basal Tg could help us in determining which patients need aggressive treatment.

Clinical outcome in differentiated thyroid carcinoma and microcarcinoma

INTRODUCTION

Due to the frequent use of neck ultrasonography, the incidence of differentiated thyroid microcarcinoma (DTMC), defined as a lesion with greatest dimension ≤1 cm, is increasing worldwide. Although DTMC generally has a lower aggressivity and a better prognosis than differentiated thyroid carcinoma (DTC), some cases of clinically aggressive DTMC were found. The aim of this study is to compare the rate of recurrence in DTMC and DTC, during a 3-year follow-up.

METHODS

Patients with differentiated thyroid carcinoma, who underwent total thyroidectomy and postoperative (131)I-RAI ablation, were stratified according to lesion diameter (DTC for diameter > 1 cm or DTMC ≤ 1 cm). After surgery, patients underwent a 3-year follow-up. Recurrent disease was defined on the basis of positive biochemical (Tg > 2 ng/ml under TSH-suppression or after rhTSH-stimulation) and/or imaging (US, WBS, CT, PET/CT) findings.

RESULTS

449 patients have been included in the final analysis. Linfoadenectomy rate and RAI ablative dose were significantly higher in DTC than in DTMC (32.7% vs. 22.4%, p = 0.018 and 112.3 ± 21 vs. 68.3 ± 24.1 mCi, p < 0.001). During the follow-up, 50 carcinoma recurrences occurred, more frequent in DTC than in DTMC (15.6% vs. 7.6%, p = 0.010). After adjustment for gender, age, rate of lymph node dissection and 131I dose of RAI treatment, the difference in the risk of recurrence was no longer significant among DTC and DTMC patients (HR: 1.585, 95% CI 0874-2877, p = 0.130).

CONCLUSIONS

The prediction of disease severity cannot be based exclusively on lesion diameter. A more careful therapeutic approach and follow-up should be recommended in DTMC patients.