Thyroglobulin antibodies in differentiated thyroid cancer

Antithyroglobulin Antibody Variation During Follow-Up Has a Good Prognostic Value for Preoperative Antithyroglobulin Antibody-Positive Differentiated Thyroid Cancer Patients: A Retrospective Study in Southwest China

OBJECTIVE

Antithyroglobulin antibody (TgAb) is a potential tumour marker for detecting differentiated thyroid cancer (DTC) recurrence, but insufficient data have supported its clinical applications. Our study aimed to describe the changing trend of TgAb after surgery and identify the relationship between this trend and clinical outcomes.

PATIENTS AND METHODS

We reviewed the electronic records of 1,686 DTC patients who had undergone total thyroidectomy (TT) and radioactive iodine (¹³¹I) therapy at West China Hospital of Sichuan University from January 2015 to December 2017. Finally, 289 preoperative TgAb-positive DTC patients were included and divided into four subgroups depending on the clinical outcome: Group A (tumour free), Group B (uncertain), Group C (incomplete biochemical response), and Group D (structural disease). The patient demographics, tumour characteristics, operations, pathology reports, and all serological biomarkers were reviewed and compared, and the prognostic efficacy of TgAb was evaluated.

RESULTS

Among all 1,686 patients, 393 (23.65%) were TgAb positive (>40 IU/ml) preoperatively. The TgAb level in Group A decreased significantly after surgery and ¹³¹I therapy and stabilised at a low level after 1-2 years of ¹³¹I therapy. However, in the other three groups, the decrease in TgAb was not significant after treatment. Conversely, TgAb declined slowly and remained stable or increased. The variations in TgAb relative to the preoperative level of Group A were significantly larger than those of Groups B, C, and D at most time points of follow-up (p < 0.001). By receiver operating characteristic (ROC) analyses, the variations of TgAb > -77.9% at 6 months after ¹³¹I therapy (area under the curve (AUC) = 0.862; p < 0.001) and TgAb > -88.6% at 2 years after ¹³¹I therapy (AUC = 0.901; p < 0.001) had good prognostic efficacy in tumour-free survival. When the variation in TgAb > -88.6% at 2 years after ¹³¹I therapy was incorporated as a variable in the American Thyroid Association (ATA) categories, both intermediate- and high-risk patients also had a significantly increased chance of being tumour free (from 75.68% to 93.88% and 42.0% to 82.61%, respectively).

CONCLUSIONS

For preoperative TgAb-positive DTC patients, variations in TgAb > -77.9% at 6 months after ¹³¹I therapy and TgAb > -88.6% at 2 years after ¹³¹I therapy had good prognostic efficacy. Their incorporation as variables in the ATA risk stratification system could more accurately predict disease-free survival.

Monitoring differentiated thyroid cancer patients with negative serum thyroglobulin

Aim: Serum antithyroglobulin antibody (TgAb) has been reported as a surrogate marker for differentiated thyroid cancer (DTC) in some conditions. We investigated changes in serum TgAb levels after stimulation with thyroid- stimulating hormone (TSH) and the clinical implications for monitoring DTC. Patients, methods: We retrospectively enrolled 53 DTC patients who had undergone total thyroidectomy and were negative for serum Tg and positive for TgAb. Patients underwent highdose radioactive iodine treatment, and serum TgAb was measured before (TgAbBAS) and after TSH stimulation (TgAbSTIM). TgAb was followed up 6 to 12 months later (TgAbF/U). The change in TgAb after TSH stimulation ΔTgAb- STIM) was calculated as a percentage of the baseline level. Patient disease status was classified into no residual disease (ND) and residual or recurred disease (RD) by follow-up imaging studies and pathologic data. The characteristics and diagnostic value of serum TgAb levels and ΔTgAbST|M were investigated with respect to disease status. Results: 38 patients were in the ND group and 15 were in the RD group. TgAbBAS, TgAbSTIM and TgAbF/U were significantly higher in the RD compared to the ND group (p = 0.0008, 0.0002, and < 0.0001, respectively). ΔTgAbSTIM was also significantly higher in the RD group (p = 0.0009). In the patients who presented with obviously high (> 50%) or low (< -50%) ΔTgAbSTIM, the proportions in the RD group were markedly different at 100% and 7%, respectively. ΔTgAbSTIM had significant diagnostic value for RD (p < 0.001). Conclusion: The change in serum TgAb level after TSH stimulation is different between the RD and ND groups, and thus, it may be used as a surrogate diagnostic marker for DTC when the serum Tg is negative and TgAb is positive.

Antithyroglobulin Antibody as a Marker of Successful Ablation Therapy in Differentiated Thyroid Cancer

The aim of this study was to determine the role of antithyroglobulin antibody (ATA) serum as a marker of successful I-131 ablation therapy in differentiated thyroid cancer (DTC) patients with low serum thyroglobulin (Tg). A retrospective study was conducted on 60 patients (10 males and 50 females). All patients underwent posttotal thyroidectomy and received 2.96 to 3 GBq I-131 ablation. Subjects were divided into two groups with succesful and unsuccessful I-131 ablation therapies. The data of age, gender, histopathologic type, tumor size, and metastasis were collected. Preablation serum Tg and ATA level (Tg1 and ATA1) 6–12 months after ablation (Tg2 and ATA2) were measured. The success of ablation therapy was evaluated by diagnostic whole body scan (DxWBS) 6–12 months after ablation. There were no significant differences in age, gender, type of histopathology, tumor size, and nodal metastasis between the two groups. ATA2 ≤30 kIU/L were found in 23 (62.2%) subjects with successful ablation therapy, and ATA2 >30 kIU/L in 16 (69.6%) subjects belonged to the unsuccessful group (P = 0.017). Changes between ATA1 and ATA2 levels did not differ significantly in both the groups (P = 0.062). Tg1 <10 mg/L was found in 26 (57.8%) subjects with successful therapy (P = 0.037). Multivariate analysis showed ATA2 and Tg1 as the independent factors for the success of ablation therapy (P = 0.007 and 0.015). Adjusted odds ratio of postablation ATA was 5.379 [95% confidence interval (CI) 1.590 to 18.203] and preablation Tg was 5.822 (95% CI 1.418 to 23.902). ATA levels at 6–12 months after ablation, by considering the preablation Tg levels, is a useful marker to determine successful ablation therapy in WDTC patients with low serum Tg. Changes in serum ATA levels, although not statistically significant, can provide additional information about the course of the disease.

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.

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.

Serum oncofetal fibronectin (onfFN) mRNA in differentiated thyroid carcinoma (DTC): large overlap between disease-free and metastatic patients

AIM

This study assessed if onfFN mRNA in the peripheral blood of patients with DTC can identify individuals with metastatic disease.

METHODS

Comparison of onfFN mRNA was made among 3 groups: disease-free, lymph node metastasis, and distant metastasis using real-time RT-PCR on 5 ml blood samples from each DTC patient.

RESULTS

Fifty-one patients were included: 30 (59%) were disease-free; 7 (13.7%) had lymph node metastasis; and 14 (27.5%) had distant metastasis. OnfFN mRNA levels in the 3 groups were significantly different (P=0.001) but with a large overlap and the expression being highest in the disease-free group. Subgroup analysis of the metastatic groups did not show any effect of age, cell type, and serum TSH, Tg, and antiTg on onfFN mRNA. The within-run and between-run root mean square coefficients of variations were <2%.

CONCLUSION

OnfFN mRNA in patients with DTC cannot identify those with metastatic disease.

Measuring Thyroglobulin Concentrations in Patients with Differentiated Thyroid Carcinoma

Thyroid carcinomas are the most common malignant endocrine tumors. Thyroglobulin (Tg), a specific thyroid protein, is the most important tumor marker in thyroid oncology. After total thyroidectomy or radioiodine therapy, detectable or increasing serum Tg levels in patients with differentiated thyroid carcinoma indicate persistence of active thyroid tissue or cancer recurrence. Serum Tg concentration primarily reflects three variables: the mass of differentiated thyroid tissue present; the degree of thyrotropin receptor stimulation and the intrinsic ability of the tumor to synthesize and secrete Tg. Measurement of serum Tg by current immunometric (IMA) and radioimmunological (RIA) assays encounters some methodological problems which can diminish its clinical importance. Discrepancy between the results for Tg using different methods may be caused by: different reference materials, specific properties of the primary and secondary antibodies for antigenic determinants on Tg and diverse binding affinities of these epitopes, together with interference by serum factors (usually antibodies to Tg (TgAb)) with the primary and secondary Tg antibodies from the diagnostic set. In the presence of endogenous TgAb, Tg values measured by immunoradiometric assay (IRMA) and similar assays are usually lower than the real concentrations, while in RIA apparently lower or higher results can be obtained. Falsely low values may lead to delay in necessary treatment, while an inappropriately high Tg value can cause patient anxiety and unnecessary scans. Despite current methodological limitations, serum Tg measurement is a useful test for determining worsening disease and monitoring the effects of therapy in patients who have undergone surgery for differentiated thyroid carcinoma.

Thyroglobulin antibody is associated with increased cancer risk in thyroid nodules

BACKGROUND

The association between autoimmune thyroiditis (AIT) and thyroid cancer is still not clear despite many previous reports. This study investigated whether serologic thyroid antibodies are predictive of thyroid cancer in patients with thyroid nodules.

METHOD

We retrospectively reviewed records of patients with thyroid nodules evaluated by ultrasonography-guided fine-needle aspiration cytology at our institution between January 2006 and December 2008. Thyroid autoimmunity was assessed by measuring thyroglobulin antibody (TgAb) and thyroid peroxidase antibody (TPOAb). The final outcome deciding a benign or malignant status involved a combination of cytology and histology.

RESULTS

Of the 1638 patients, malignant nodules had a higher rate of positive TgAb (30.8% vs. 19.6%; p < 0.001) and elevated thyrotropin (TSH) levels (2.5 +/- 2.8 mIU/L vs. 2.1 +/- 2.0 mIU/L; p = 0.021) than benign nodules. The rate of positive TPOAb was not higher in malignant nodules, although both TPOAb and TgAb were well correlated with TSH levels and histological AIT. In the multivariate analysis, a positive TgAb was significantly associated with thyroid cancer (odds ratio [OR] = 1.61, 95% confidence interval [CI] 1.12-2.33) with upper tertile of normal range of TSH levels (OR = 1.72, 95% CI 1.12-2.63) and above normal range of TSH levels (OR = 1.98, 95% CI 1.06-3.70).

CONCLUSION

We report for the first time that a positive serum TgAb test was an independent predictor for thyroid malignancy in thyroid nodules along with serum TSH levels regardless of the presence of AIT. Our results suggest that TgAb measurement could give additional information for predicting malignancy in cytologically indeterminate thyroid nodules in conjunction with clinical risk factors and TSH levels.

Recurrence detection in differentiated thyroid cancer patients with elevated serum level of antithyroglobulin antibody: special emphasis on using (18)F-FDG PET/CT

OBJECTIVE

A clinical challenge is presented by differentiated thyroid cancer (DTC) patients who show increased serum antithyroglobulin antibody (TgAb) level with undetectable thyroglobulin (Tg) and negative radioiodine whole body scan (I-WBS). The aim of this study is to investigate the recurrence in DTC patients with elevated TgAb by using (18)F-FDG PET/CT (PET/CT) in addition to I-WBS and neck ultrasonography (USG).

SUBJECTS AND DESIGN

A total of 276 TgAb+ patients were enrolled. Recurrence was assessed and compared between TgAb+ and TgAb- patients. TgAb+ patients were further categorized into two groups of 35-140 U/ml (Group A) and 140 U/ml or greater (Group B), according to receiver operating characteristic (ROC) curve analysis. Tumoural status was evaluated regarding the TgAb positivity and the degree of increase of TgAb.

RESULTS

Thirty-seven (13.4%) of 276 TgAb+ patients were finally diagnosed with recurrence, compared with 21 (13.5%) of 156 TgAb- patients (P = 0.987). There was a correlation between TgAb level and recurrence (P = 0.032). Recurrence was more common in Group B than Group A (27.8% and 9.9%, respectively, P = 0.001). Recurrence was found in 37.5% of 24 TgAb+/Tg- patients who showed a gradually increasing tendency in serial measurements of TgAb. Sixteen cervical foci (21.1%) missed on neck USG and 17 lesions (22.4%) located outside the neck were additionally detected with PET/CT in TgAb+ patients.

CONCLUSIONS

TgAb plays a complementary role to Tg in the detection of recurrence of DTC. Tumour recurrence was more frequent in patients with elevated TgAb level over 140 U/ml or a trend toward increasing levels. PET/CT could provide additional information to I-WBS and neck USG in detecting tumour recurrence in patients with elevated TgAb.

Change of serum antithyroglobulin antibody levels is useful for prediction of clinical recurrence in thyroglobulin-negative patients with differentiated thyroid carcinoma

OBJECTIVES

The aim of the study was to evaluate the usefulness of the antithyroglobulin autoantibody (TgAb) value at 6-12 months after remnant ablation in predicting recurrence in differentiated thyroid carcinoma patients who had undetectable thyroglobulin (Tg) values. The change in TgAb concentration measured between the time of remnant ablation (TgAb1) and 6-12 months thereafter (TgAb2) was also evaluated as a possible prognostic indicator.

PATIENTS AND METHODS

Patients with differentiated thyroid carcinoma who underwent total thyroidectomy followed by (131)I remnant ablation between 1995 and 2003 at the Asan Medical Center (Seoul, Korea) were enrolled. Of these, 824 patients with undetectable Tg at 6-12 months after remnant ablation during thyroid hormone withdrawal were the subjects of this study.

RESULTS

TgAb2 was positive in 56 patients. Ten of 56 patients (18%) with positive TgAb2 had recurrence, whereas only 10 of 768 patients (1%) with negative TgAb2 had recurrence during 73.6 months of follow-up (P < 0.001). The change between TgAb1 and TgAb2 levels was evaluated in patients with positive TgAb2. TgAb concentration decreased by more than 50% in 21 patients (group 1) and by less than 50% in 16 patients (group 2), and it increased in 19 patients (group 3). The recurrence rates in groups 1, 2, and 3 were 0, 19, and 37%, respectively (P = 0.016).

CONCLUSIONS

Serum TgAb levels measured at 6-12 months after remnant ablation could predict recurrence in patients with undetectable Tg values. In patients with undetectable Tg and positive TgAb values, a change in TgAb concentration during the early postoperative period may be a prognostic indicator of recurrence.

Clinical importance of anti-thyroglobulin auto-antibodies in patients with differentiated thyroid carcinoma: Comparison with 99mTc-MIBI scans

AIMS

(1) To investigate whether elevated serum anti-thyroglobulin antibody (ATG) reflects the recurrence of cancer in patients with differentiated thyroid carcinoma (DTC) in whom thyroglobulin was undetectable after radioiodine ablation. (2) To assess the sensitivity of disease detection for (99m)Tc-MIBI whole-body scans (WBSs) in these patients and investigate the correlation between MIBI WBS results and high serum ATG levels.

MATERIALS AND METHODS

In this retrospective study, we evaluated 14 patients (13 women and 1 man; mean age 44 +/- 19 years) with DTC who underwent total or near-total thyroidectomy followed by an ablative dose of I at various time intervals. According to histopathological findings, 10 patients (71.4%) who were diagnosed as having papillary carcinoma and four patients (28.6%) as having follicular cell carcinoma, had high serum ATG concentrations (> 40 IU x ml(-1); range, 62-2000 IU x ml(-1)), but low serum thyroglobulin concentrations (< 1.6 ng x ml). Post-therapeutic and diagnostic (131)I WBSs and (99m)Tc-MIBI WBSs were performed. Scans were visually evaluated for detecting recurrence. If necessary, bone scans, chest X-rays, computerized tomography, ultrasonography and histopathological evaluation were performed.

RESULTS

Recurrent and/or persistent disease was found in 12 of the patients. This was confirmed pathologically in four patients and by using other imaging methods in eight (bone scans, computerized tomography, ultrasonography). The sensitivity and specificity of disease detection for MIBI WBSs was 66.7% and 100%, respectively. For (131)I WBSs, the sensitivity of disease detection was 55.6%. Among these 12 patients, 10 responded to treatment (three underwent surgery, seven received radioiodine therapy, and two had surgery + radioiodine therapy). ATG levels decreased in eight of the 10 patients, but remained persistently elevated in two despite treatment.

CONCLUSIONS

(1) Persistently elevated ATG levels appear to serve as a useful marker for recurrent or persistent DTC in patients with undetectable serum tyroglobulin levels. Thus, the routine measurement of ATG antibody in such patients is of great value. (2) In these patients, (99m)Tc-MIBI has a relatively high sensitivity in the diagnosis of a recurrence of thyroid cancer or metastases. So, in patients with elevated ATG but undetectable serum thyroglobulin levels, (99m)Tc-MIBI can be used to determine whether there is a recurrence of DTC or metastases.

Development and clinical impact of thyroglobulin antibodies in patients with differentiated thyroid carcinoma during the first 3 years after thyroidectomy

OBJECTIVE AND DESIGN

Cross-sectional studies have reported an increased prevalence of circulating thyroglobulin autoantibodies (TgAbs) in patients with differentiated thyroid carcinoma (DTC). With the advent of more sensitive assays, a longitudinal study monitoring the development of TgAb levels after ablative therapy was warranted.

METHODS

One hundred and twelve consecutive patients with follicular cell-derived thyroid cancer were followed for 3 years. All patients had been thyroidectomized and received, on average, two radioiodine therapies. Residual tissue was quantified scintigraphically by 131I 24-h uptake. TgAb and thyroglobulin (Tg) serum levels were determined with a sensitive direct radioligand assay and an IRMA respectively.

RESULTS

The prevalence of TgAbs at the initial examination was 29% (median 130 U/ml). During follow-up, TgAb levels rose transiently in one-tenth of the patients, but the prevalence of demonstrable TgAbs decreased to < 10% after 3 years. The median serum half-life of TgAbs in treated DTC patients was 10 weeks. At initial examination (when all patients still had residual thyroid tissue and 17 had metastases), rising TgAb levels were correlated with the inability to detect Tg in 4, 30 and 73% of the patients, when initial TgAbs were < 6, 6-50 or > 50 U/ml respectively. While the Tg recovery test was valid for all patients, an in vitro dilution assay with TgAb serum reduced Tg values by up to 32%.

CONCLUSIONS

The development and course of TgAbs in DTC patients cannot be predicted by initial or residual tumour volume, TgAb or Tg levels. The presence of TgAbs, even in low concentrations, may cause Tg underestimation despite valid recovery tests in DTC patients.

Thyroglobulin antibodies in serum of patients with differentiated thyroid cancer: relationship between epitope specificities and thyroglobulin recovery

BACKGROUND

Serum antibodies against thyroglobulin (TgAbs) are common in patients with differentiated thyroid cancer (DTC) and can interfere in thyroglobulin (Tg) assays. We identified the epitopes on Tg recognized by TgAb-positive sera from patients with DTC and examined the association between epitope specificity patterns and Tg recovery.

METHODS

We tested 50 DTC sera for Tg epitope specificity, TgAbs, and Tg recovery. Epitope recognition was determined by use of a panel of 10 well-characterized Tg monoclonal antibodies directed against 6 Tg antigenic clusters (I-VI) in competitive reactions with test sera. Tg was measured by the Thyroglobuline IRMA (CIS bio international). Recovery of added Tg (TgREC) was determined by an in-house assay.

RESULTS

Epitope recognition was restricted to immunodominant clusters in 58% of patients, whereas the rest were either broadly heterogeneous (16%) or nonreactive (26%). Median Tg recovery did not differ between sera with restricted and unrestricted specificities (69% vs 80%; P >0.05). TgREC was inversely correlated with the total number of epitopes recognized by sera (r = -0.66; P <0.001).

CONCLUSIONS

TgAbs with both restricted and broad specificities are present in patients with DTC. TgAb interference is related to the number of epitopes recognized by sera rather than the pattern of epitope recognition.

Thyroglobulin: a specific serum marker for the management of thyroid carcinoma

Thyroglobulin measurements in tissue and serum play an integral role in the evaluation of patients who have thyroid cancer. Immunohistochemical detection of thyroglobulin in surgical specimens is useful in the differential diagnosis of tumors of unknown origin; however, the most important application of thyroglobulin measurement in clinical practice is in the postsurgical management of differentiated thyroid cancer. Serum thyroglobulin is a highly specific and sensitive tumor marker for detecting persistent or recurrent thyroid cancer and for monitoring clinical status. The reappearance of circulating thyroglobulin after total thyroid ablation is pathognomonic for the presence of tumor. The measurement of thyroglobulin in serum is challenging, however, and several analytical problems limit assay performance. Thyroglobulin autoantibody interference is a particularly significant concern that requires all thyroglobulin samples to be screened for their presence. No immunoassay is totally free from interference by thyroglobulin autoantibodies. Measurement of thyroglobulin mRNA to detect circulating tumor cells may help to overcome some of the limitations of current protein-detection methods; serum thyroglobulin will continue to remain the "gold standard." The complex functional features of thyroid carcinomas make sole reliance upon any one diagnostic technique, including thyroglobulin assessments, potentially misleading. Thyroglobulin measurements are a critical component of a multifaceted diagnostic approach to this disease.

Impact of previous thyroid autoimmune diseases on prognosis of patients with well-differentiated thyroid cancer

Autoimmune phenomena are frequently associated with differentiated thyroid carcinomas. However, the significance of thyroid gland autoimmune aggression on the outcome of these patients is still controversial. To address this issue, we studied 173 patients (123 with papillary and 50 with follicular carcinomas) who underwent surgery complemented by radioiodine ablation and followed up for 0.5-29 (6 +/- 5.76) years. Analysis of the prognostic factors revealed that higher age, male gender, larger nodule size, follicular tumors, presence of metastases at diagnosis, grade of differentiation, and stage correlated positively with the occurrence of death, metastasis and/or recurrence, while the presence of antibodies and the previous history of autoimmune disease correlated negatively with these events. Long distant metastases increased the odds for a lower disease-free rate for patients with papillary (8.366 times) and follicular (7.373 times) carcinoma. However, univariate and multivariate analysis failed to demonstrate that neck node involvement could influence the outcome for patients with well-differentiated thyroid carcinoma. The odds for patients with previous history of thyroid autoimmune disease (p < 0.02) or with thyroid autoantibodies (p < 0.001) to have a worse outcome were lower than for patients with no evidence of autoimmune activity, suggesting that autoimmune activity against the gland may exert a protective effect on the outcome of differentiated thyroid carcinoma patients.

Clinical significance of elevated level of serum antithyroglobulin antibody in patients with differentiated thyroid cancer after thyroid ablation

OBJECTIVE

This study was designed to investigate whether an elevated serum antithyroglobulin antibody (TgAb) reflects cancer recurrence in thyroglobulin (Tg)-undetectable patients with differentiated thyroid carcinoma (DTC) after thyroid ablation.

DESIGN

We measured serum TgAb level and evaluated the disease status in 226 DTC patients who had undergone remnant ablation and showed an undetectable Tg result as assessed by immunoradiometric assay.

MEASUREMENTS

Radioligand assay of TgAb was performed. Recurrence was assessed by 131I scan, 18F-fluorodeoxyglucose positron emission tomography, sonography, computed tomography, or by surgical operation.

RESULTS

Fifty-one patients (22.6%) of the Tg-undetectable patients showed positive TgAb, and 25 (49.0%) of these were confirmed with recurrence. The recurrence rate of TgAb-positive patients was higher than that of TgAb-negative patients (3.4%; P < 0.0001). During follow-up, 73.1% of the disease-free patients showed spontaneously decreased TgAb levels. A total of 71.4% of patients with recurrent cancer, who showed responses to surgical operation or radio-iodine treatment, also showed a decreased TgAb level.

CONCLUSIONS

Persistently elevated TgAb levels appear to serve as a useful marker for recurrent or persistent DTC in patients with undetectable serum Tg results. Thus, the routine measurement of TgAb in such patient populations may be indicated.

High-sensitivity human thyroglobulin (hTG) immunoradiometric assay in the follow-up of patients with differentiated thyroid cancer

Circulating human thyroglobulin (hTG) measurement has a pivotal role in the management of patients affected by differentiated thyroid cancer (DTC). Generally, hTG serum concentration less than 1 ng/ml is considered a marker of complete remission after total thyroid ablation. Recently, high-sensitivity immunoradiometric assays (IRMA) have been developed to detect very low hTG serum concentrations. The present study was undertaken to test a newly developed high-sensitivity hTG IRMA and to evaluate its diagnostic performance and reproducibility in the follow-up of patients affected by DTC. We retrospectively selected 156 patients without signs of recurrence and 39 patients with DTC recurrence. Serum samples were collected during L-thyroxine (T4) suppressive therapy (ONT4) and 4 weeks after T4 withdrawal (OFFT4), and hTG was measured by a specific high-sensitivity IRMA (DYNOtest Tg-plus, BRAHMS Diagnostica GmbH, Berlin, Germany). Sera showing the presence of antibodies against hTG (AbhTG) or hTG-recovery less than 80% were excluded from the study. The receiver operator characteristic (ROC) curve analysis was performed to select the best cut-off levels, and diagnostic performance of the marker was evaluated. By using ONT4 cut-off level of 0.2 ng/ml and OFFT4 cut-off level of 0.5 ng/ml we obtained a sensitivity/specificity/accuracy profile of 0.92/0.98/0.97 and 0.97/0.98/0.98, respectively. We found false-negative results in three (12%) and one (4%) out of 24 patients with cervical recurrence by using 0.2 and 0.5 ng/ml cut-off levels, respectively. However, we found false-negative results in 13 (54%) and six (25%) patients when 1.0 ng/ml cut-off level was used. Finally, DYNOtest Tg-plus showed a very satisfactory intra- and inter-assay reproducibility in the very low hTG concentration range. Based on our data, we conclude that DYNOtest Tg-plus assay is effective and accurate in evaluation of patients with DTC.

Serum thyroglobulin measurement. Utility in clinical practice

Serum thyroglobulin measurement has greatly facilitated the clinical management of patients with differentiated thyroid cancer and a variety of other thyroid disorders. Thyroglobulin autoantibodies remain a significant obstacle to the clinical use of thyroglobulin measurement. The interpretation of any given thyroglobulin value requires the careful synthesis of all pertinent clinical and laboratory data available to the clinician. The diagnostic use of rhTSH-stimulated thyroglobulin levels has greatly facilitated the follow-up of low-risk patients with thyroid cancer. Although the measurement of thyroglobulin mRNA from peripheral blood is likely to affect the future management of these patients, it is expected that serum thyroglobulin measurement will continue to have a principal role in the care of patients with differentiated thyroid cancer.

False positive 131I whole body scans in thyroid cancer

Well differentiated thyroid cancer is a rare disease in the UK. It is the only cancer which, having metastasized, remains curable by radioisotope therapy with 131I. The main indication for administering repeat doses of 131I is the appearance of abnormal uptake in a whole body scan following diagnostic or therapeutic 131I administration. False positive scans, showing the presence of 131I uptake in the absence of residual thyroid tissue or metastases can occur, although they are uncommon. Unless recognized as a false positive, 131I uptake may result in diagnostic error and lead to administration of an unnecessary therapy dose. We describe a series of nine patients in whom the scans showed false positive uptake of 131I, including cases where the cause of the uptake is still uncertain. We demonstrate the common sites of false positive uptake, discuss the underlying mechanisms and suggest a systematic approach to the interpretation of whole body scans in order to prevent unnecessary treatment with 131I.

Recurrent differentiated thyroid cancer without elevation of serum thyroglobulin

Thyroglobulin (Tg) is a reliable tumor marker in patients with well-differentiated thyroid cancer (WDTC). We identified 11 patients who had undetectable serum Tg and no thyroglobulin antibody (TgAb) in the presence of clinical disease. Three had residual disease after ablation of the thyroid by surgery plus radioiodine and 8 relapsed after a disease-free interval. Histologic review confirmed that 7 of the tumors were papillary carcinomas and 4 were follicular carcinomas. Immunohistochemical staining for Tg was positive in 6 of 7 papillary and in 3 of 4 follicular carcinomas. There were no identifiable histologic or clinical features that could be used to predict further patients who may relapse with absence of this serum marker. Negative serum Tg did not appear to be an adverse prognostic feature. During follow-up, measurement of Tg and TgAb should be supplemented by radioiodine scanning and radiological imaging in patients in whom recurrence is likely or suspected.