Diagnostic Performance of [18F]TFB PET/CT Compared with Therapeutic Activity [131I]Iodine SPECT/CT and [18F]FDG PET/CT in Recurrent Differentiated Thyroid Carcinoma

[18F]tetrafluoroborate ([18F]TFB) is an emerging PET tracer with excellent properties for human sodium iodide symporter (NIS)-based imaging in patients with differentiated thyroid cancer (DTC). The aim of this study was to compare [18F]TFB PET with high-activity posttherapeutic [131I]iodine whole-body scintigraphy and SPECT/CT in recurrent DTC and with [18F]FDG PET/CT in suspected dedifferentiation. Methods: Twenty-six patients treated with high-activity radioactive [131I]iodine therapy (range, 5.00-10.23 GBq) between May 2020 and November 2022 were retrospectively included. Thyroid-stimulating hormone was stimulated by 2 injections of recombinant thyroid-stimulating hormone (0.9 mg) 48 and 24 h before therapy. Before treatment, all patients underwent [18F]TFB PET/CT 40 min after injection of a median of 321 MBq of [18F]TFB. To study tracer kinetics in DTC lesions, 23 patients received an additional scan at 90 min. [131I]iodine therapeutic whole-body scintigraphy and SPECT/CT were performed at a median of 3.8 d after treatment. Twenty-five patients underwent additional [18F]FDG PET. Two experienced nuclear medicine physicians evaluated all imaging modalities in consensus. Results: A total of 62 suspected lesions were identified; of these, 30 lesions were [131I]iodine positive, 32 lesions were [18F]TFB positive, and 52 were [18F]FDG positive. Three of the 30 [131I]iodine-positive lesions were retrospectively rated as false-positive iodide uptake. Tumor-to-background ratio measurements at the 40- and 90-min time points were closely correlated (e.g., for the tumor-to-background ratio for muscle, the Pearson correlation coefficient was 0.91; P < 0.001; n = 49). We found a significant negative correlation between [18F]TFB uptake and [18F]FDG uptake as a potential marker for dedifferentiation (Pearson correlation coefficient, -0.26; P = 0.041; n = 62). Conclusion: Pretherapeutic [18F]TFB PET/CT may help to predict the positivity of recurrent DTC lesions on [131I]iodine scans. Therefore, it may help in the selection of patients for [131I]iodine therapy. Future prospective trials for iodine therapy guidance are warranted. Lesion [18F]TFB uptake seems to be inversely correlated with [18F]FDG uptake and therefore might serve as a dedifferentiation marker in DTC.

Diagnostic significance of MRI versus CT using identical PET data in patients with recurrent differentiated thyroid cancer: A PET/MRI study

In this retrospective study we compared magnet resonance imaging (MRI) and computed tomography (CT) each combined with identical 2-deoxy-2-[18F] fluoro-D-glucose or 2-[18F] F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) data in patients with recurrent differentiated thyroid cancer (DTC). In total 42 patients with DTC were examined. All patients underwent FDG PET/MRI and CT, the latter originating from one of the following examinations: I-131 single photon emission computed tomography/CT (32/42), low dose FDG PET/CT (5/42) or diagnostic FDG PET/CT (5/42). Two readers assessed FDG PET/MRI as well as FDG PET/CT, with the latter CT coming from one of the above examinations performed at a maximum temporal interval of 5 days from PET/MRI. Local recurrence, cervical lymph node - and pulmonary metastases were assessed in a consensus read. Lesions rated with a high malignancy score (score 4 or 5) were further analyzed. Every malignant lesion was verified if it was identified by one of both or by both modalities. In 20 of 42 patients altogether 100 malignant lesions were present. In 11/20 patients in total 15 local recurrences (15 in MRI/ 9 in CT: 9 CT/MRI, 6 MRI only, 0 CT only; P = .04) were found with a statistically significant better performance of MRI. Regarding lymph node metastases, in total 13 lesions (12 in MRI/ 8 in CT: 7 CT/MRI, 5 MRI only, 1 CT only; P = .22) in 8/20 patients were found with no significant difference between both modalities. Furthermore, in 9/20 patients in total 72 lung lesions (40 in MRI/ 63 in CT: 31 CT/MRI, 9 MRI only, 32 CT only; P = .001) were found with a statistically significant better performance of CT. In 33/42 patients follow up was available and supported the observations. In patients with recurrent DTC, PET/MRI showed superiority compared to PET/CT in evaluation of the neck region. PET/MRI was inferior to PET/CT in evaluation of the lung. PET/MRI in combination with a low dose CT of the lung may thus represent the ideal staging tool in patients with recurrent DTC.

Additive value of 18FDG-PET/CT to positive 131I whole body scan in recurrent differentiated thyroid cancer patients with potential influence on treatment strategy: single Egyptian center experience

Background

Years ago the utility of of18F-fluorodeoxyglucose-positron emission tomography/computerized tomography (18FDG-PET/CT) in differentiated thyroid cancer was confined mainly to cases with elevated serum thyroglobulin and negative 131I whole body scan. In this study, we try to assess the diagnostic performance of 18FDG-PET/CT in recurrent differentiated thyroid cancer patients with positive 131I whole body scan and in addition to evaluate the impact of 18FDG-PET/CT on the treatment strategy.

Results

The 18FDG PET/CT detected tumor recurrence in 35 (81.3%) patients most of them (91.4%) were in stage IV, while the rest 8.5% was in stage III. No recurrence was detected among patients in stage II and III by 18FDG PET/CT.

Regarding lesion-based analysis, sensitivity of 18FDG-PET/CT was superior to that of 131I post-therapeutic whole body scan (TxWBS) (78.2% vs. 69.4%, respectively), while both modalities had the same specificity (50%). 18FDG-PET/CT changed the treatment plan in 18 (41.6%) patients.

Conclusion

18FDG-PET/CT may be complementary to 131ITxWBS in high-risk DTC with impact on treatment strategy.

Incremental diagnostic value of [18F]tetrafluoroborate PET-CT compared to [131I]iodine scintigraphy in recurrent differentiated thyroid cancer

INTRODUCTION

Efficient therapy of recurrent differentiated thyroid cancer (DTC) is dependent on precise molecular imaging techniques targeting the human sodium iodide symporter (hNIS), which is a marker both of thyroid and DTC cells. Various iodine isotopes have been utilized for detecting DTC; however, these come with unfavorable radiation exposure and image quality ([131I]iodine) or limited availability ([124I]iodine). In contrast, [18F]tetrafluoroborate (TFB) is a novel radiolabeled PET substrate of hNIS, results in PET images with high-quality and low radiation doses, and should therefore be suited for imaging of DTC. The aim of the present study was to compare the diagnostic performance of [18F]TFB-PET to the clinical reference standard [131I]iodine scintigraphy in patients with recurrent DTC.

METHODS

Twenty-five patients with recurrent DTC were included in this retrospective analysis. All patients underwent [18F]TFB-PET combined with either CT or MRI due to newly discovered elevated TG levels, antiTG levels, sonographically suspicious cervical lymph nodes, or combinations of these findings. Correlative [131I]iodine whole-body scintigraphy (dxWBS) including SPECT-CT was present for all patients; correlative [18F]FDG-PET-CT was present for 21 patients. Histological verification of [18F]TFB positive findings was available in 4 patients.

RESULTS

[18F]TFB-PET detected local recurrence or metastases of DTC in significantly more patients than conventional [131I]iodine dxWBS and SPECT-CT (13/25 = 52% vs. 3/25 = 12%, p = 0.002). The diagnosis of 6 patients with cervical lymph node metastases that showed mildly increased FDG metabolism but negative [131I]iodine scintigraphy was changed: [18F]TFB-PET revealed hNIS expression in the metastases, which were therefore reclassified as only partly de-differentiated (histological confirmation present in two patients). Highest sensitivity for detecting recurrent DTC had the combination of [18F]TFB-PET-CT/MRI with [18F]FDG-PET-CT (64%).

CONCLUSION

In the present cohort, [18F]TFB-PET shows higher sensitivity and accuracy than [131I]iodine WBS and SPECT-CT in detecting recurrent DTC. The combination of [18F]TFB-PET with [18F]FDG-PET-CT seems a reasonable strategy to characterize DTC tumor manifestations with respect to their differentiation and thereby also individually plan and monitor treatment. Future prospective studies evaluating the potential of [18F]TFB-PET in recurrent DTC are warranted.

Low or Undetectable Basal Thyroglobulin Levels Obviate the Need for Neck Ultrasound in Differentiated Thyroid Cancer Patients After Total Thyroidectomy and 131I Ablation

BACKGROUND

Neck ultrasound (NUS) is currently seen as a main component of follow-up of differentiated thyroid cancer (DTC) and is usually performed regardless of non-stimulated thyroglobulin (Tg) levels. The aim of this study was to determine whether there is a clinical benefit from such a routine NUS in DTC patients.

METHODS

A retrospective database study was conducted of 3176 cervical ultrasound exams performed in 773 patients between June 15, 1996, and July 1, 2012. The accuracy of ultrasound results was assessed based on the results of further diagnostic and/or therapeutic procedures within six months of a particular ultrasound.

RESULTS

A total of 2199 NUS exams were classified as true negative, 216 as true positive, 692 as false positive in 339 (43.9%) individual patients, 170 of whom were low risk, and 69 as false negative. Thus, overall sensitivity, specificity, positive predictive value, negative predictive value, and accuracy [confidence interval] were 75.8% [70.1-81.5%], 76.1% [74.3-77.8%], 23.8% [18.1-29.5%], 97.0 [96.2-97.7%], and 76.0% [74.3-77.7%], respectively. No significant differences were found between low- and high-risk patients. There were no significant differences between patients with an undetectable and a low detectable (<1 μg/L) Tg level. However, these two groups both showed significantly lower positive predictive value and higher negative predictive value than patients with a Tg ≥1 μg/L. From January 2007 onwards, true-positive and false-negative neck ultrasounds were no longer observed in patients with Tg <1 μg/L.

CONCLUSION

After total thyroidectomy and ¹³¹I ablation, neck ultrasound should be reserved only for anti-Tg antibody negative patients with a Tg level of ≥1 μg/L.

Peace of mind for patients with differentiated thyroid cancer?

Differentiated thyroid carcinomas (DTC) have an excellent prognosis, with 10-year overall survival rates over 90%. In addition, DTC patients benefit from their lifelong medical surveillance. The aim of the study was to compare the patients’ overall survival with that of a matched general population. Patients and methods: We have analyzed 1497 consecutive patients with DTC, who underwent radioiodine therapy in Münster, Germany, according to international standards. We classified our patients according to the current 7th edition of the UICC (Union Internationale Contre le Cancer) classification and we compared the overall survival of the patients with the expected survival based on age and sex of the general population as provided by the Federal Statistical Office, Germany. Results: There were no significant differences in overall survival rates between DTC patients of the cohort in stages I to IVa compared to the expected survival based on age and sex of the general population. However, patients in stage IVc showed a significantly worse overall survival rate using the log-rank test (p < 0.0001). Conclusion: Patients with DTC showed excellent overall survival rates in stages I, II, III and IVa. All patients, except for those in stage IVc (M1 ≥ 45 years), had overall survival rates similar to the general population.

Clinical utility of 18F-FDG PET/CT in the follow-up of a large cohort of patients with high-risk differentiated thyroid carcinoma

OBJECTIVE

To evaluate the clinical utility of 18F-FDG PET/CT in patients with high-risk DTC.

SUBJECTS AND METHODS

Single-center retrospective study with 74 patients with high-risk differentiated thyroid cancer (DTC), classified in 4 groups. Group 1: patients with positive sTg or TgAb, subdivided in Group 1A: negative RxWBS and no foci of metastases identified at conventional image (n = 9); Group 1B: RxWBS not compatible with suspicious foci at conventional image or not proportional to sTg level (n = 13); Group 2: patients with histological findings of aggressive DTC variants (n = 21) and Group 3: patients with positive RxWBS (n = 31).

RESULTS

18F-FDG PET/CT identified undifferentiated lesions and helped restage the disease in groups 1B and 2. The scan helped guide clinical judgment in 9/13 (69%) patients of group 1B, 10/21 (48%) patients of group 2 and 2/31 (6%) patients of group 3. There was no clinical benefit associated with group 1A. 18F-FDG PET/CT was associated with progressive disease.

CONCLUSION

18F-FDG PET/CT is a useful tool in the follow-up of patients with high-risk DTC, mainly in the group of RxWBS not compatible with suspicious foci at conventional image or not proportional to sTg level and in those with aggressive DTC variants. Additionally, this study showed that 18F-FDG PET/CT was associated with progression and helped display undifferentiated lesions guiding clinical assessments regarding surgeries or expectant treatments.

F18-FDG-PET for recurrent differentiated thyroid cancer: a systematic meta-analysis

Background

Positron emission tomography (PET) with fluor-18-deoxy-glucose (FDG) is widely used for diagnosing recurrent or metastatic disease in patients with differentiated thyroid cancer (DTC).

Purpose

To assess the diagnostic accuracy of FDG-PET for DTC in patients after ablative therapy.

Material and Methods

A systematic search was conducted in Medline/PubMed, EMBASE, Cochrane Library, Web of Science, and Open Grey looking for all English-language original articles on the performance of FDG-PET in series of at least 20 patients with DTC having undergone ablative therapy including total thyroidectomy. Diagnostic performance measures were pooled using Reitsma’s bivariate model.

Results

Thirty-four publications between 1996 and 2014 met the inclusion criteria. Pooled sensitivity and specificity were 79.4% (95% confidence interval [CI], 73.9–84.1) and 79.4% (95% CI, 71.2–85.4), respectively, with an area under the curve of 0.858.

Conclusion

F18-FDG-PET is a useful method for detecting recurrent DTC in patients having undergone ablative therapy.

Post-PET ultrasound improves specificity of 18F-FDG-PET for recurrent differentiated thyroid cancer while maintaining sensitivity

Background

Positron emission tomography (PET) using fluor-18-deoxyglucose (18F-FDG) with or without computed tomography (CT) is generally accepted as the most sensitive imaging modality for diagnosing recurrent differentiated thyroid cancer (DTC) in patients with negative whole body scintigraphy with iodine-131 (I-131).

Purpose

To assess the potential incremental value of ultrasound (US) over 18F-FDG-PET-CT.

Material and Methods

Fifty-one consecutive patients with suspected recurrent DTC were prospectively evaluated using the following multimodal imaging protocol: (i) US before PET (pre-US) with or without fine needle biopsy (FNB) of suspicious lesions; (ii) single photon emission computed tomography (≥3 GBq I-131) with co-registered CT (SPECT-CT); (iii) 18F-FDG-PET with co-registered contrast-enhanced CT of the neck; (iv) US in correlation with the other imaging modalities (post-US). Postoperative histology, FNB, and long-term follow-up (median, 2.8 years) were taken as composite gold standard.

Results

Fifty-eight malignant lesions were identified in 34 patients. Forty lesions were located in the neck or upper mediastinum. On receiver operating characteristics (ROC) analysis, 18F-FDG-PET had a limited lesion-based specificity of 59% at a set sensitivity of 90%. Pre-US had poor sensitivity and specificity of 52% and 53%, respectively, increasing to 85% and 94% on post-US, with knowledge of the PET/CT findings (P < 0.05 vs. PET and pre-US). Multimodal imaging changed therapy in 15 out of 51 patients (30%).

Conclusion

In patients with suspected recurrent DTC, supplemental targeted US in addition to 18F-FDG-PET-CT increases specificity while maintainin sensitivity, as non-malignant FDG uptake in cervical lesions can be confirmed.

PET/CT in the management of thyroid cancers

OBJECTIVE

Thyroid cancer is the most common endocrine cancer. This review evaluates the established use of (18)F-FDG PET/CT in papillary, follicular, Hürthle cell, anaplastic, and medullary thyroid cancers. The significance of incidental diffuse and focal thyroid FDG uptake is discussed. The evolving value of non-FDG radiotracers, including (124)I, (18)F-dihydroxyphenylalanine, and (68)Ga somatostatin analogs, is summarized.

CONCLUSION

PET/CT is a valuable imaging test, in the appropriate clinical context, for the management of thyroid cancers.

Distant metastatic lesions in patients with differentiated thyroid carcinoma. Clinical implications of radioiodine and FDG uptake

AIM

Many investigators have reported an inverse relationship between iodine and glucose utilization of differentiated thyroid carcinoma (DTC) according to its degree of differentiation; however, not every DTC is compatible with this phenomenon. This study was conducted to evaluate the clinical implication of iodine and glucose uptake at distant metastatic lesions in DTC patients.

PATIENTS, METHODS

64 DTC patients (women 47; mean age 49.9 ± 16.4 years) with distant metastasis who underwent post (131)I treatment whole-body scan (RxWBS) and FDG PET/CT were included in the study. Radioiodine (RAI) and FDG uptake of metastatic lesions were evaluated. TSH stimulated serum thyroglobulin (s-Tg) were obtained.

RESULTS

53 of 64 patients (82.8%) were RAI(+) group, and 37 patients (57.8%) were FDG(+) group. Patients in the RAI(-) group showed a higher rate of FDG uptake than RAI(+) group (100.0% vs. 49.1%, p = 0.002). Patients in the FDG(-) group showed a higher rate of RAI uptake than FDG(+) group (100.0% vs. 70.3%, p = 0.002). Patients with s-Tg < 100 ng/ml were frequently observed in the FDG(-)/RAI(+) group and the FDG(+)/RAI(-) group (p = 0.023). And patients with s-Tg ≥ 500 ng/ml were more frequently observed in the FDG(+)/RAI(+) group, compared with the FDG(+)/RAI(-) group (p = 0.036). Reduced disease-specific survival (DSS) was observed in patients with RAI(-) (p = 0.003), FDG(+) (p = 0.006), SUVmax > 3.6 (p<0.001), and s-Tg > 75.8 ng/ml (p = 0.009). In multivariate analysis, only a SUVmax > 3.6 was significantly predictive of DSS (p = 0.006).

CONCLUSION

An inverse relationship between RAI and FDG uptake, flip-flop phenomenon, was observed in patients with metastatic lesions of DTC. Reduced disease-specific survival was observed in patients with FDG(+), RAI(-) in metastatic lesions, or high s-Tg value.