Diagnostic performance of 2-[18F]FDG PET/CT in recurrent differentiated thyroid cancer and elevated antithyroglobulin antibodies: an updated systematic review and bivariate meta-analysis

PURPOSE

This updated systematic review and bivariate meta-analysis aimed to investigate the diagnostic performance of 2-[18F]FDG PET/CT for the detection of recurrent disease in patients with differentiated thyroid cancer (DTC) who have negative 131I whole body scintigraphy and increased antithyroglobulin antibodies (TgAb) levels.

METHODS

The current systematic review was carried out following a preset protocol, and the "Preferred Reporting Items for a Systematic Review and Meta-Analysis" served as a guideline for its development and reporting. A comprehensive research of the PubMed/MEDLINE, Embase and Cochrane library databases was conducted until June 2024.

RESULTS

Between 2002 and 2023, 13 studies (608 patients) published on this topic were selected. The pooled sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 2-[18F]FDG PET or PET/CT were 84% (95%CI: 78-87%), 82% (95%CI: 78-86%), 72% (95%CI: 67-76%), 90% (95%CI: 87-93%) and 83% (95%CI: 79%-86%) respectively. The pooled positive and negative likelihood ratios (LR+ and LR - ) and the diagnostic odds ratio (DOR) were 0.180 (95%CI: 0.128-0.253), 3.214 (95%CI: 2.357-4.383), and 17.863 (95%CI: 10.475-30.462), respectively. No statistically significant heterogeneity among the studies was found for all the metrics evaluated (I2 < 50%).

CONCLUSIONS

2-[18F]FDG PET/CT demonstrated a good diagnostic performance in patients with DTC and increased TgAb. Although more studies are warranted, the provided evidence-based data should support the integration of 2-[18F]FDG PET/CT in clinical and diagnostic guidelines on DTC patients with increased TgAb.

[Diagnosis of lymph node metastases from papillary thyroid carcinoma by measuring thyroglobulin in the puncture needle. Calculation of optimal cut-off point in our series]

Fine-needle aspiration cytology (FNAC), used in suspicious cervical lymph nodes of unknown origin is frequently inconclusive and prone to false negatives. In order to evaluate the usefulness of measuring thyroglobulin in the washing with saline solution of the puncture needle for the diagnosis of metastasis of papillary carcinoma of the thyroid, an optimal thyroglobulin cutting point has to be calculated, being positive or negative depending on whether the thyroglobulin levels are higher or lower than the cutting point. We have retrospectively studied 33 patients (19 women and 14 men) with an average age of 49.3 years, with papillary carcinoma of the thyroid and suspected lymph node metastasis. Of them 16 (47.1%) had a positive FNAC. To determine thyroglobulin predictive capacity with regards to the metastasis of papillary carcinoma of the thyroid a ROC analysis was carried out with an under curve area UCA: 0.987 (CI 95%: 0.808-1.000) obtaining, using Youden's J statistic, 0.4 ng/ml as the thyroglobulin cutting point with best predictive capacity. The study of the relationship between thyroglobulin and the preservation/non-preservation of the thyroid showed statistically significant differences (P=.023). Our results validate 0.4 ng/ml of thyroglobulin as an optimal cutting point of the presence of metastasis of papillary carcinoma of the thyroid in lymph nodes. When reviewing the bibliography, a great diversity of cutting points may be found, which is explained mainly by the great inter-observer and inter-assay variability. That is why we recommend calculating each laboratory's own optimal cutting point; and determine in subsequent studies two cutting points depending on whether or not thyroid is preserved.

Diagnostic, Theranostic and Prognostic Value of Thyroglobulin in Thyroid Cancer

Thyroglobulin (Tg) is an iodinated glycoprotein, which is normally stored in the follicular colloid of the thyroid, being a substrate for thyroid hormone production. Since it is produced by well-differentiated thyroid cells, it is considered a reliable tumor marker for patients with differentiated thyroid carcinoma (DTC) during their follow-up after total thyroidectomy and radioiodine ablation. It is used to monitor residual disease and to detect recurrent disease. After total thyroid ablation, unstimulated highly sensitive Tg measurements are sufficiently accurate to avoid exogenous or endogenous thyrotropin (TSH) stimulation and provide accurate diagnostic and prognostic information in the great majority of DTC patients. Adopting sophisticated statistical analysis, i.e., decision tree models, the use of Tg before radioiodine theranostic administration was demonstrated to be useful in refining conventional, pathology-based risk stratification and providing personalized adjuvant or therapeutic radioiodine administrations. The follow-up of DTC patients aims to promptly identify patients with residual or recurrent disease following primary treatment. Our review paper covers the diagnostic, theranostic and prognostic value of thyroglobulin in DTC patients.

Thyroglobulin and thyroglobulin antibody: an updated clinical and laboratory expert consensus

OBJECTIVE

Thyroglobulin measurement is the cornerstone of modern management of differentiated thyroid cancer, with clinical decisions on treatment and follow-up based on the results of such measurements. However, numerous factors need to be considered regarding measurement with and interpretation of thyroglobulin assay results.

DESIGN

The present document provides an integrated update to the 2013 and 2014 separate clinical position papers of our group on these issues.

METHODS

Issues concerning analytical and clinical aspects of highly-sensitive thyroglobulin measurement will be reviewed and discussed based on an extensive analysis of the available literature.

RESULTS

Thyroglobulin measurement remains a highly complex process with many pitfalls and major sources of interference, especially anti-thyroglobulin antibodies, need to be assessed, considered and, when necessary, dealt with appropriately.

CONCLUSIONS

Our expert consensus group formulated 53 practical, graded recommendations for guidance on highly-sensitive thyroglobulin and TgAb in laboratory and clinical practice, especially valuable where current guidelines do not offer sufficient guidance.

Utility of Stimulated Thyroglobulin in Reclassifying Low Risk Thyroid Cancer Patients' Following Thyroidectomy and Radioactive Iodine Ablation: A 7-Year Prospective Trial

Context

Following total thyroidectomy and radioactive iodine (RAI) ablation, serum thyroglobulin levels should be undetectable to assure that patients are excellent responders and at very low risk of recurrence.

Objective

To assess the utility of stimulated (sTg) and non-stimulated (nsTg) thyroglobulin levels in prediction of patients outcomes with differentiated thyroid cancer (DTC) following total thyroidectomy and RAI ablation.

Method

A prospective observational study conducted at a University Hospital in Saudi Arabia. Patients diagnosed with differentiated thyroid cancer and were post total thyroidectomy and RAI ablation. Thyroglobulin levels (nsTg and sTg) were estimated 3-6 months post-RAI. Patients with nsTg <2 ng/ml were stratified based on their levels and were followed-up for 5 years and clinical responses were measured.

Results

Of 196 patients, nsTg levels were <0.1 ng/ml in 122 (62%) patients and 0.1-2.0 ng/ml in 74 (38%). Of 122 patients with nsTg <0.1 ng/ml, 120 (98%) had sTg levels <1 ng/ml, with no structural or functional disease. sTg levels >1 occurred in 26 (35%) of patients with nsTg 0.1-2.0 ng/ml, 11 (15%) had structural incomplete response. None of the patients with sTg levels <1 ng/ml developed structural or functional disease over the follow-up period.

Conclusion

Suppressed thyroglobulin (nsTg < 0.1 ng/ml) indicates a very low risk of recurrence that does not require stimulation. Stimulated thyroglobulin is beneficial with nsTg 0.1-2 ng/ml for re-classifying patients and estimating their risk for incomplete responses over a 7 years follow-up period.

Comparison between a new thyroglobulin assay with the well-established Beckman Access immunoassay: A preliminary report

OBJECTIVES

Measurement of serum thyroglobulin (Tg) plays a key role in the post-thyroidectomy management of differentiated thyroid carcinoma (DTC). In this context, the performance of new-generation thyroglobulin assay has clinical implications in the follow-up of DTC patients. Aim of this study was to compare the new highly sensitive Liaison Tg II (Tg-L) with the well-established Tg Access assay (Tg-A).

MATERIALS AND METHODS

A total of 91 residual serum samples (23 positive and 68 negatives for Tg auto-antibodies) were tested by the Beckman Access and Diasorin Liaison assays. Study samples were from 21 patients with pathologically proven DTC and control samples from 70 (16 patients with benign thyroid disease and 54 apparently healthy subjects).

RESULTS

Our results showed that Tg-L was highly correlated with Tg-A for both values ranging between 0.2 and 50 ng/mL (Pearson's r = 0.933 [95%CI 0.894-0.958], P < .001) and higher than 50 ng/mL (Pearson's r = 0.849 [95%CI 0.609-0.946], P < .001). For Tg values lower than 0.2 ng/mL, the overall concordance rate was 92%. Moreover, we tested 7 fine-needle aspiration washout fluids (FNA), showing an overall concordance rate in discriminating negative and positive of 100%. Finally, we found no interference by Tg auto-antibodies (TgAbs) for both Tg-L and Tg-A. Conversely, rheumatoid factor (RF) interferes with Tg-A, but not with Tg-L in one patient with no relapsing thyroid carcinoma.

CONCLUSIONS

Liaison Tg II demonstrated a good correlation with Access Tg assay both for sera and FNAs. Further studies on larger population are needed to evaluate Tg-L clinical impact on DTC patient's follow-up.

Circulating biomarkers for the detection of tumor recurrence in the postsurgical follow-up of differentiated thyroid carcinoma

PURPOSE OF REVIEW

To discuss advances and challenges in thyroglobulin and Tg-antibody (TgAb) measurement and their impact on clinical management of differentiated thyroid carcinoma (DTC).

RECENT FINDINGS

Basal high-sensitive Tg (hsTg) measurement avoids the need for stimulation and greatly simplifies DTC patients' management. In addition, patients with undetectable hsTg after thyroid ablation are at a very low risk of recurrence and can be safely managed by periodic hsTg measurement alone. When TgAb is present, its trend over time serves as primary (surrogate) tumor marker. However, an undetectable hsTg measurement appears to indicate a complete remission of DTC even in the presence of TgAb. Finally, reliable reference values are not yet available for low-risk DTC who are treated with less than total thyroid ablation, and caution is needed before well-designed studies addressing these issues have been published.

SUMMARY

The use of hsTg assays has changed paradigms for DTC monitoring even in the presence of TgAb, and greatly reduced patients' discomfort and overall case-management costs. Reliable Tg interpretation criteria are urgently needed for patients treated with less than total thyroid ablation.

Additional value of a high sensitive thyroglobulin assay in the follow-up of patients with differentiated thyroid carcinoma

OBJECTIVE

Thyroglobulin (Tg) is an excellent tumour marker, as detectable or increasing Tg levels are highly indicative of persistent or recurrent differentiated thyroid carcinoma (DTC). The clinical value of a highly sensitive (hs)-Tg assay in patients with DTC has not yet been established. The aim of this study was to investigate the additional value of unstimulated hs-Tg measurements (Tg-on) compared to stimulated IRMA-Tg measurements (Tg-off) in the follow-up of patients with DTC.

DESIGN, PATIENTS, MEASUREMENTS

We retrospectively studied patients treated for DTC between 2006 and 2013 and compared hs-Tg and IRMA-Tg measurements. The study group consisted of 99 DTC patients in remission; Tg-on was measured 3 months after remnant ablation and Tg-off 6 months after ablation.

RESULTS

In the study group, 44 patients showed a hs-Tg-on <0·15 μg/l (functional sensitivity); of these, 43 had an IRMA-Tg-off measurement <1·0 μg/l, resulting in a negative predictive value of 97·7% and a positive predictive value of 56·4%.

CONCLUSIONS

The hs-Tg-on measurement is able to predict patients with an IRMA-Tg-off <1·0 μg/l, and therefore decreases the need for Tg stimulation after ablation.

Comparison of Thyroglobulin Measurements Using Three Different Immunoassay Kits: A BRAMHS Tg-Plus RIA Kit, a BRAMHS hTg Sensitive Kryptor Kit, and a Beckman Coulter ACCESS Immunoassay Kit

BACKGROUND

Second-generation thyroglobulin immunometric assays (Tg-IMAs) have been developed with improved sensitivity. Our aim was to compare the diagnostic value of Tg-IMA measurements using a Kryptor (BRAHMS AG) kit (Tg-K) and an ACCESS (Beckman Coulter) kit (Tg-A) with that of the first-generation Tg measurement using a Tg-plus (BRAHMS AG) kit (Tg+).

METHODS

We enrolled 82 differentiated thyroid cancer patients who underwent total thyroidectomy with radioactive iodine remnant ablation and who underwent diagnostic whole body scan using recombinant human thyroid stimulating hormone (rhTSH). The Tg+, Tg-K, and Tg-A were measured before rhTSH administration during levothyroxine treatment (suppressed Tg) from the same sample. Serum Tg+ was measured after rhTSH stimulation (stimulated Tg).

RESULTS

Suppressed Tg+ was more significantly correlated with suppressed Tg-K (R²=0.919, P<0.001) than with suppressed Tg-A (R²=0.536, P<0.001). The optimal cut-off values of suppressed Tg+, Tg-K, and Tg-A for predicting stimulated Tg+ of 1 ng/mL were 0.3, 0.2, and 0.2 ng/mL, respectively. The sensitivity, specificity, and accuracy of suppressed Tg+ were 67%, 100%, and 90%, respectively; those of suppressed Tg-K were 83%, 90%, and 88%; those of suppressed Tg-A were 96%, 82%, and 87%, respectively. The positive predictive and negative predictive values of Tg+ were 100% and 87%, respectively; those of Tg-K were 79% and 92%; and those of Tg-A were 73% and 98%.

CONCLUSION

We could not clearly demonstrate which kit had better diagnostic performance after comparison of first-generation Tg measurements with Tg-IMA measurements. Also, there were kit-to-kit variations between Tg-IMA kits. Suppressed Tg measured by Tg-IMA was insufficient to completely substitute for a stimulated Tg measurement.

Any detectable thyroglobulin in lymph node biopsy washouts suggests local recurrence in differentiated thyroid cancer

The sensitivity of local recurrence detection in differentiated thyroid cancer (DTC) is increased by measuring thyroglobulin in needle washouts from lymph node fine-needle aspiration biopsies (FNA-Tg). Recent studies have proposed minimum diagnostic threshold values for FNA-Tg and have reported interference from Tg antibodies (Tg Ab), leading to low or false-negative results. The aim of this study was to assess the utility of FNA-Tg in the diagnosis of local DTC recurrence in patients referred to a single pathology service used by our tertiary teaching hospital, the first such study in an Australian cohort. Data were collected from the pathology service database for FNA-Tg over an 18-month period, and the results of 69 FNA-Tg samples from 57 patients were obtained. FNA-Tg findings were compared with cytology and histology when patients proceeded to surgery. Using the functional sensitivity as the cut-off, detectable FNA-Tg (≥0.9 μg/l) had a sensitivity of 95.7%, specificity of 50% and positive predictive value of 95.7%. Our results suggest that detectable FNA-Tg leads to histological confirmation of local nodal DTC recurrence and would support a decision to proceed to surgery. Serum Tg Ab can, however, interfere with FNA-Tg measurements. Thus, we now recommend routine use of FNA-Tg washouts in all lymph node FNA biopsies for the detection of DTC recurrence.

Thyroglobulin measurement using highly sensitive assays in patients with differentiated thyroid cancer: a clinical position paper

Differentiated thyroid cancer (DTC) is the most common endocrine cancer and its incidence has increased in recent decades. Initial treatment usually consists of total thyroidectomy followed by ablation of thyroid remnants by iodine-131. As thyroid cells are assumed to be the only source of thyroglobulin (Tg) in the human body, circulating Tg serves as a biochemical marker of persistent or recurrent disease in DTC follow-up. Currently, standard follow-up for DTC comprises Tg measurement and neck ultrasound combined, when indicated, with an additional radioiodine scan. Measurement of Tg after stimulation by endogenous or exogenous TSH is recommended by current clinical guidelines to detect occult disease with a maximum sensitivity due to the suboptimal sensitivity of older Tg assays. However, the development of new highly sensitive Tg assays with improved analytical sensitivity and precision at low concentrations now allows detection of very low Tg concentrations reflecting minimal amounts of thyroid tissue without the need for TSH stimulation. Use of these highly sensitive Tg assays has not yet been incorporated into clinical guidelines but they will, we believe, be used by physicians caring for patients with DTC. The aim of this clinical position paper is, therefore, to offer advice on the various aspects and implications of using these highly sensitive Tg assays in the clinical care of patients with DTC.

Thyroglobulin in lymph node fine-needle aspiration washout: a systematic review and meta-analysis of diagnostic accuracy

CONTEXT

The thyroglobulin measurement in the needle washout after fine-needle aspiration (FNA) has been reported to increase the sensitivity of FNA in identifying lymph node (LN) metastases from differentiated thyroid cancer (DTC).

OBJECTIVE

The aim of the study was to estimate the diagnostic accuracy of this technique.

DATA SOURCES

To identify eligible studies, we searched electronic databases for original articles in English from 1975 through 2013.

STUDY SELECTION

Studies that enrolled participants with suspicious neck LNs during thyroid nodule workup or thyroid cancer follow-up were included.

DATA EXTRACTION

Working independently, authors used a standard form to extract data. For quality assessment, QUADAS2 guidelines were applied.

DATA SYNTHESIS

Including all the selected studies (24 studies, 2865 LNs) in the pooled analysis, overall sensitivity was 95.0% (95% confidence interval [CI], 93.7-96.0%), specificity was 94.5% (95% CI, 93.2-95.7%), and diagnostic odds ratio (DOR) was 338.91 (95% CI, 164.82-696.88) with significant heterogeneity (inconsistency [I(2)] = 65.7%; heterogeneity, P < .001). Stratifying different populations and including only patients with thyroid gland (410 LNs), pooled sensitivity was 86.2% (95% CI, 80.9-90.5%), specificity was 90.2% (85.1-94.0%), and DOR was 56.621 (22.535-142.26; I(2) = 37.3%; heterogeneity, P = .121). Including only patients after thyroidectomy (1007 LNs), pooled sensitivity was 96.9% (95% CI, 94.9-98.2%), specificity was 94.1% (91.7-96.0%), and DOR was 407.65 (198.67-836.46; I(2) = 0.0%; heterogeneity, P = .673).

CONCLUSIONS

Thyroglobulin measurement in washout from LN FNA has high accuracy in early detection of nodal metastases from DTC. The technique is simple, but a better standardization of criteria for patient selection, analytical methods, and cutoff levels is required.

Preablation Stimulated Thyroglobulin/TSH Ratio as a Predictor of Successful I(131)Remnant Ablation in Patients with Differentiated Thyroid Cancer following Total Thyroidectomy

Background. About 90% of thyroid cancers are differentiated thyroid cancers. Standard treatment is total thyroidectomy followed by radioactive I(131)remnant ablation and TSH suppression with thyroxine. Unsuccessful ablation drastically affects the prognosis of patients with DTC particularly high risk individuals; therefore, identifying the factors that affect the success of ablation is important in the management of patients with DTC. sTg is a good predictor of successful ablation in DTC. Its levels can be influenced by tumor staging and TSH values, as well as other factors. Therefore, we did this study using TSH to correct the predictive value of sTg in success of RRA. Methods. We retrospectively reviewed the records of 75 patients with DTC, who underwent total thyroidectomy followed by RRA and TSH suppression. Results. Preablation sTg and sTg/TSH ratio are significantly associated with ablation outcome. Cutoff value for sTg to predict successful and unsuccessful ablation was 18 ng/mL with 76.7% sensitivity and 79.1% specificity, while for sTg/TSH cutoff was 0.35 with 81.4% sensitivity and 81.5% specificity (P < 0.001). Association was stronger for sTg/TSH ratio with adjusted odds ratio (AOR) 11.64 (2.43-55.61) than for sTg with AOR 5.42 (1.18-24.88). Conclusions. Preablation sTg/TSH ratio can be considered as better predictor of ablation outcome than sTg, tumor size, and capsular invasion.

Unstimulated highly sensitive thyroglobulin in follow-up of differentiated thyroid cancer patients: a meta-analysis

CONTEXT

Serum thyroglobulin (Tg) is an indicator of differentiated thyroid cancer (DTC) relapse.

OBJECTIVE

Our objective was to conduct a meta-analysis of published data about the diagnostic performance of highly sensitive serum Tg (hsTg) during levothyroxine therapy in DTC follow-up.

DATA SOURCES

We performed a comprehensive literature search of PubMed/MEDLINE and Scopus for studies published until July 2013.

STUDY SELECTION

Studies investigating the diagnostic performance of basal hsTg in monitoring DTC were eligible. Exclusion criteria were 1) articles not within the field of interest; 2) reviews, letters, or conference proceedings; 3) articles evaluating serum Tg measurement with a functional sensitivity >0.1 ng/mL; 4) overlap in patient data; and 5) insufficient data to reassess diagnostic performance of basal serum hsTg.

DATA EXTRACTION

Information was collected concerning basic study data, patient characteristics, and technical aspects. For each study, the number of true-positive, false-positive, true-negative, and false-negative findings for basal hsTg, considering stimulated Tg measurement as a reference standard, were recorded.

DATA SYNTHESIS

Pooled data demonstrated that the negative predictive value of hsTg was 97% and 99% considering a stimulated Tg measurement >1 ng/mL and >2 ng/mL as cutoffs for positivity, respectively. Despite the high pooled sensitivity of basal hsTg, the pooled specificity, accuracy, and positive predictive value were insufficient to completely substitute for a stimulated Tg measurement.

CONCLUSIONS

Basal hsTg measurement has a very high negative predictive value but an insufficient positive predictive value for monitoring DTC patients. Therefore, a Tg stimulation test can be avoided in patients with an undetectable basal hsTg, whereas a stimulated Tg measurement should be considered when hsTg levels are detectable.

Efficacy analysis of (131)I therapy and predictive value of preablation stimulated thyroglobulin for lung metastases from differentiated thyroid cancer

OBJECTIVE

Our objective was to investigate the clinical efficacy of (131)I therapy for lung metastases from differentiated thyroid cancer (DTC) and assess whether the preablation stimulated thyroglobulin (Tg) could have predictive value for the outcome.

METHODS AND MATERIALS

Fifty-two DTC patients (mean 44.5±19.2years; 33 females and 19 males) with lung metastases treated with (131)I were retrospectively analysed. The therapeutic efficacy was evaluated based on the change in serum Tg. Fifty patients' preablation stimulated Tg were collected with negative Tg antibody levels and estimated using the t-test method.

RESULTS

After (131)I therapy, a significant decrease in serum Tg was seen in 30 patients (effective rate, 57.6%), and changes in serum Tg that indicated stabilization and ineffectiveness were both seen in 11 patients (21.2%). Only patients with age under 45years were more likely to respond to serum Tg changes (P=0.046). But binary logistic regression revealed that none of the six factors (age, patient gender, pathological type, local lymph node involvement, size of metastases, and (131)I uptake by metastases) had statistically significant impacts on the efficacy analysis (all P>0.05). For analysing with the preablation stimulated Tg, the "Fine miliaric" and (131)I uptake positive with great prognosis group was much lower than any other group (all the P<0.05).

CONCLUSION

(131)I therapy is a feasible and effective treatment for DTC lung metastases. A better prognosis would be accomplished in those who had low level of preablation stimulated Tg in DTC patient with lung metastases.

Postsurgery serum thyroglobulin disappearance kinetic in patients with differentiated thyroid carcinoma

BACKGROUND

Knowing the postsurgery thyroglobulin (Tg) kinetic would enable its rationale for use in patients with differentiated thyroid cancer (DTC). Heterogeneous results were previously reported, then we aimed to evaluate the postsurgery Tg kinetic in a large group of patients with DTC.

METHODS

Enrolled were 96 patients with DTC. Serum Tg was measured first at 5 minutes, then at 24, 48, 72, 96, and 120 hours after thyroidectomy. The Tg half-life (Tg[t(1/2)]) was estimated in a 1-compartment model. A simplified 2-point formula (24 and 120 hours) was also used.

RESULTS

The mean Tg(t(1/2)) was 28.53 to 30.22 hours in 1-compartment model and 27.39 hours when estimated by a simplified formula. A strong inter-methods relationship was found (p < .001).

CONCLUSIONS

A reliable Tg(t(1/2)) estimation could be obtained by a simplified formula requiring only 2 postsurgery Tg measurements (24 and 120 hours, respectively).