F-18 FDG PET/CT in the management of thyroid cancer

PET/CT in the management of differentiated thyroid cancer

The standard treatment of differentiated thyroid cancer (DTC) consists of surgery followed by iodine-131 (¹³¹I) administration. Although the majority of DTC has a very good prognosis, more aggressive histologic subtypes convey a worse prognosis. Follow-up consists of periodically measurements of serum thyroglobulin, thyroglobulin antibodies and neck ultrasound and ¹²³I/¹³¹I whole-body scan. However, undifferentiated thyroid tumors have a lower avidity for radioiodine and the ability of DTC to concentrate ¹³¹I may be lost in metastatic disease. Positron emission tomography (PET)/computed tomography (CT) has been introduced in the evaluation of patients with thyroid tumors and the 2-[18F]-fluoro-2-deoxyd-glucose (¹⁸F-FDG) has been largely validated as marker of cell's metabolism. According to the 2015 American Thyroid Association guidelines, ¹⁸F-FDG PET/CT is recommended in the follow-up of high-risk patients with elevated serum thyroglobulin and negative ¹³¹I imaging, in the assessment of metastatic patients, for lesion detection and risk stratification and in predicting the response to therapy. It should be considered that well-differentiated iodine avid lesions could not concentrate ¹⁸F-FDG, and a reciprocal pattern of iodine and ¹⁸F-FDG uptake has been observed. Beyond ¹⁸F-FDG, other tracers are available for PET imaging of thyroid tumors, such as Iodine-124 (¹²⁴I), ¹⁸F-tetrafluoroborate and Gallium-68 prostate-specific membrane antigen. Moreover, the recent introduction of PET/MRI, offers now several opportunities in the field of patients with DTC. This review summarizes the evidences on the role of PET/CT in management of patients with DTC, focusing on potential applications and on elucidating some still debating points.

Role of Thyroglobulin Doubling Time in Differentiated Thyroid Cancer and Its Relationship with Demographic-Histopathologic Risk Factors and 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Parameters

Background: Aim of this study was to investigate the relationship between thyroglobulin doubling time (TgDT) and basal risk factors and metabolic parameters derived from ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in differentiated thyroid cancer (DTC). Materials and Methods: An analysis of 95 DTC patients who had rising serum thyroglobulin (Tg) levels under levothyroxine (LT4) suppression after radioiodine therapy was made. TgDT was calculated for 28/95 patients. The relationship between TgDT and basal demographic and histopathologic risk factors, preablative Tg, and antithyroglobulin antibody (ATg) levels and metabolic parameters was analyzed. Results: In 28 patients (15M, 13F, mean age: 52.6 ± 17.6) that TgDT could be calculated, ¹⁸F-FDG PET/CT was positive in 12 patients. Median TgDT was lower in ¹⁸F-FDG PET/CT positive patients compared to the negative cases (p < 0.05). Patients with skeletal metastasis or local recurrence had a shorter DT compared to the patients with lung metastasis. TgDT was correlated with peak standardized uptake value (SUV_peak) (p < 0.05). Maximum standardized uptake value (SUV_max) was correlated with tumor size (p < 0.05) and mean standardized uptake value (SUV_mean) with tumor size and vascular invasion (p < 0.05). Median SUV_max and SUV_mean were higher in follicular cancer or poor histological variants of papillary DTC compared to papillary cancer classical variant patients Conclusion: TgDT may be predictive of a positive ¹⁸F-FDG PET/CT in DTC. Skeletal metastasis and local recurrence are related to shorter TgDT. Greater tumor size, vascular invasion, and follicular cancer or poor variants of papillary carcinoma are related with higher SUV_max and SUV_mean. Larger scale studies are needed to confirm results and to calculate a possible cutoff of TgDT for a positive ¹⁸F-FDG PET/CT study.

Head-to-head comparison of F-18 FDG PET/CT in radioidine refractory thyroid cancer patients with elevated versus suppressed TSH levels a pilot study

Introduction

To perform a head-to-head comparison of the uptake pattern of F-18 fluorodeoxyglucose in positron emission computed tomography (FDG PET/CT) in radioiodine refractory thyroid carcinomas (RAIR) in the same patient under elevated TSH levels (eTSH) and suppressed TSH levels (sTSH).

Methods

FDG PET/CT studies were performed under two conditions: levothyroxine intake (sTSH) and 30 days after hormonal withdrawal (eTSH). SUVmax values and the number of lesions detected (local recurrence and metastases in cervical and distant lymph nodes, lungs and bone) where blindly evaluated. Blood serum TSH and Tg levels were obtained prior to both studies. FDG PET/CT imaging, neck ultrasound, biopsy and follow-up were considered the reference standard.

Results

Fifteen patients performed both eTSH and sTSH FDG PET/CT studies. Both were positive for metastases in 80% of the patients. eTSH FDG PET/CT studies did not reveal increased uptake (p = 0.0640) and did not demonstrate a higher number of lesions (p = 0.320) when compared to sTSH FDG PET/CT studies. There was no change in the clinical management of these patients.

Conclusions

eTSH FDG PET/CT in patients with RAIR did not show more metastases in comparison to sTSH FDG PET/CT and there was no impact in clinical management of patients. Elevating TSH levels (whether by hormonal withdrawal or recombinant TSH) in patients being submitted to FDG PET/CT may not be necessary.

Usefulness of 68Ga-DOTA-RGD (αvβ3) PET/CT Imaging in Thyroglobulin Elevation With Negative Iodine Scintigraphy

TENIS (thyroglobulin elevation with negative iodine scintigraphy) syndrome in patients with differentiated thyroid carcinoma is not a rare finding. In such patients, F-FDG PET/CT can help in disease evaluation. RGD tripeptide, used for imaging angiogenesis, may also help in disease detection in patients with negative radioiodine whole-body scan. We present 1 such case in whom Ga-RGD tripeptide imaging was helpful in disease detection in the setting of negative radioiodine whole-body scan.

Thyroid incidentalomas on 18FDG-PET/CT: a metabolico-pathological correlation

Background

Thyroid incidentaloma is defined as an unsuspected thyroid lesion found on imaging study or while performing a surgery non-related to the thyroid gland. Most recent scientific literature tends to demonstrate a detection rate of 0.1–4.3% for incidental findings of thyroid focal uptake identified by ¹⁸F-fluorodeoxyglugose Positron Emission Tomography with computed tomography (¹⁸FDG-PET/CT) initially prescribed for nonthyroid disease. From 10.3 to 80.0% of patients who underwent further evaluation are diagnosed with malignant lesions.

Our first objective is to determine the risk of malignancy confined in thyroid incidentalomas(IT) detected on ¹⁸FDG-PET/CT in patients treated in a tertiary care center (Centre Hospitalier Universitaire de Sherbrooke). Second, we want to identify a cut-off value for SUVmax in order to distinguish benign from malignant IT. Third, we look for predictive criterion that can be outlined to help in their management.

Methods

We retrospectively reviewed 40 914 charts of patients who had a ¹⁸FDG-PET/CT done in a tertiary center from 2004 to 2014. For each patient where a thyroid incidentaloma has been identified, Maximum Standardized Uptake Value (SUVmax), ultrasound report, cytology and histopathological results as well as oncologic outcomes were compiled and analyzed.

Results

In this study, the incidence for thyroid incidentaloma detected with ¹⁸FDG-PET/CT is 0.74%. The rate of malignancy present in IT is 8.2% based on histopathological results. Of the patients who underwent surgery, thyroid malignancy was identified in 54.3% of them. Cytoponction showed a strong correlation with final histopathological results (p = 0.009).

Conclusion

Thyroid incidentalomas detected with ¹⁸FDG-PET/CT are relatively infrequent, but the potential risk of malignancy remains elevated. Fine needle aspiration biopsy is the investigation of choice to rule out a malignant incidentaloma when there is no other element in the clinical portrait to preclude such additional work up.

Prognostic role of 18F-FDG PET/CT in the postoperative evaluation of differentiated thyroid cancer patients

PURPOSE

The aim of this study was to evaluate the role of F-FDG PET/CT performed after surgery but before radioiodine therapy in patients with differentiated thyroid cancer.

PROCEDURES

FDG PET/CT was performed off l-thyroxine in 60 newly diagnosed differentiated thyroid cancer patients. Clinical and hematological evaluation as well as high-resolution neck ultrasound were performed. All patients underwent a complete follow-up (range, 6-67 months; mean [SD], 31.7 [20.6] months). The date of recurrence or the most recent office visit was recorded. Progression-free survival (PFS) is the primary end point of this study. Analysis was performed by Cox proportional hazards model. Survival curves were generated using Kaplan-Meier estimates, and the log-rank test was used to assess significance.

RESULTS

FDG PET/CT was negative in 63% of patients, 20% had FDG thyroid bed uptake, 5% distant metastases, and 12% lymph node FDG uptake. In patients with positive FDG PET/CT scan (ie, those with distant metastases or lymph node uptake), a higher rate of recurrence was observed (50% vs 6%, P < 0.05). Thyroglobulin, neck ultrasound, stage, and FDG PET/CT correlated with PFS at univariate analysis. At multivariate analysis, only thyroglobulin and FDG PET/CT continued to be predictors of PFS. Patients with a negative FDG PET/CT scan have a better PFS either in the whole group or in those with elevated thyroglobulin level (both >2 ng/mL and >10 ng/mL).

CONCLUSIONS

FDG PET/CT was abnormal in 17% of patients. Moreover, FDG PET/CT has an independent prognostic role, with a better PFS in patients with a negative scan.

The prevalence and predictors of active brown adipose tissue in Chinese adults

OBJECTIVE

Previous studies have shown that active brown adipose tissue (BAT) is present in adults and may play important roles in the regulation of energy homeostasis. However, nearly every study has been carried out in patients undergoing scanning for cancer surveillance (CS), whose metabolism and BAT activity may not reflect those of healthy individuals. The objective of this study was to investigate the prevalence and predictors of active BAT in Chinese adults, particularly in healthy individuals.

DESIGN

A total of 31,088 consecutive subjects aged ≥18 years who had undergone positron emission tomography/computed tomography (PET/CT) scanning of BAT were evaluated in this study.

METHODS

We measured BAT activity via (18)F-fluorodeoxyglucose PET/CT in subjects who had undergone scanning for either a routine medical checkup (MC) or CS in Shanghai. Then, we investigated the predictors of active BAT, particularly in healthy individuals.

RESULTS

In both groups, the prevalence of BAT was higher in women than in men. Using a multivariate logistic analysis, we found age, sex, BMI, and high thyroid glucose uptake to be significant predictors of BAT activity in the MC group. Similarly, we found age, sex, and BMI to be significant predictors of BAT activity, but not thyroid high glucose uptake, in the CS group.

CONCLUSIONS

In Chinese adults, BAT activity inversely correlates with BMI and thyroid high glucose uptake, which reinforces the central role of brown fat in adult metabolism and provides clues to a potential means for treating the metabolic syndrome.

Therapeutic impact of (18)F-FDG PET/CT in recurrent differentiated thyroid carcinoma

PURPOSE

(18)F-fluorodeoxyglucose-positron emission tomography/computed tomography (PET/CT) has proved effective in detecting recurrent or metastatic differentiated thyroid carcinoma (DTC) in the follow-up of operated DTC patients with high thyroglobulin (Tg) levels and negative findings on radioiodine whole-body scan. The aim of this retrospective study was to assess the impact of PET/CT on the planning of appropriate treatment for known recurrent disease in operated DTC patients.

MATERIALS AND METHODS

The study concerned 44 consecutive DTC patients (36 papillary, 8 follicular), who underwent total thyroidectomy and thyroid remnant ablation with (131)I and PET/CT. All patients had proven or strongly suspected recurrent disease judging from neck ultrasound (US) and fine-needle aspiration cytology, and detectable basal Tg levels.

RESULTS

PET/CT findings were positive in 25/44 patients (56.81 %) and negative in 19. A positive PET/CT result predicted resectable tumour recurrences in 19/25 patients, but also detected additional tumour sites that prompted changes to the treatment plan in 6/25 patients (24 %). A negative PET/CT result led to clinical monitoring for 11/19 patients (57.89 %).

CONCLUSIONS

PET/CT can help select patients, who might benefit from a tailored therapy by improving the detection of local recurrences not apparent on neck US or metastases.

Relationship between the immunohistochemistry of the primary tumour and 18F-FDG-PET/CT at recurrence in patients with well-differentiated thyroid carcinoma

PURPOSE

In patients thyroidectomized for well-differentiated thyroid carcinoma, the correlation between thyroglobulin (Tg) plasma level and F-fluoro-2-deoxy-D-glucose (F-FDG)-PET results is still a matter of debate. We evaluated whether the immunochemical profile of the primary tumour could be used as a predictor of positivity on F-FDG-PET/computed tomography (CT) when recurrence is confirmed.

MATERIALS AND METHODS

A total of 26 patients (eight men, 18 women; 51±16 years old) were included. All of the patients had a histologically proven recurrence or a high level of Tg during follow-up and underwent a F-FDG-PET/CT following two intramuscular injections of rhTSH. The F-FDG-PET/CT scans were blindly analysed by three nuclear physicians. The results of the PET scans were classified as true positive, false positive or false negative. Nine antibodies were used for the immunochemical analysis (tissue microarray: hexokinase I, II and III; Tg; vascular endothelial growth factor; and glucose transporter type 1, CD31, CD68 and sodium iodide symporter).

RESULTS

The PET scans were positive for 15 patients and negative for 11 patients. Hexokinase I was expressed in nine of the 26 primary tumours (7/26 for the isoforms). No single molecule expressed in the primary tumours was correlated with the F-FDG-PET/CT results. There was no association of antibody overexpression (clustering) in the primary tumours with the F-FDG-PET/CT results of the recurrences.

CONCLUSION

In a larger series, we failed to confirm the preliminary results of Hooft and colleagues. This study did not allow for the determination of a single marker expressed in the primary tumours that would be predictive of F-FDG-PET/CT positivity when recurrence is suspected. Therefore, at present, immunochemistry does not appear to be a definitive tool for predicting the results of F-FDG-PET/CT in cases of recurrence.

FDG PET/CT in the detection of metastases in a patient with Tg and 131I WBS negative follicular thyroid cancer

After a total or near total thyroidectomy and radioiodine ablation therapy for differential thyroid cancer (DTC), routine follow-up methods are (131)I or (131)I whole-body scanning (WBS) as well as serum thyroglobulin (Tg) and anti-thyroglobulin (anti-Tg) levels. We describe a case of a 41-year-old woman with follicular thyroid cancer. Although serum Tg level and (131)I WBS were negative after radioiodine ablation therapy, she had pain around her left medial clavicle. FDG PET/CT was performed for any undetected metastases. FDG PET/CT showed hypermetabolic bone metastases in the left medial clavicle. Biopsy confirmed metastases of the thyroid follicular carcinoma.

Increasing the yield of recombinant thyroid-stimulating hormone-stimulated 2-(18-fluoride)-flu-2-deoxy-D-glucose positron emission tomography-CT in patients with differentiated thyroid carcinoma

OBJECTIVE

The aim of this study was to assess the accuracy of recombinant thyroid-stimulating hormone (rTSH)-stimulated 2-(18-fluoride)-flu-2-deoxy-D-glucose ((18)F-FDG) positron emission tomography (PET)-CT in detecting recurrence in patients with differentiated thyroid cancer.

METHODS

Consecutive (18)F-FDG PET-CT scans performed with rTSH stimulation between 2007 and 2010 in patients with a history of papillary or follicular thyroid carcinoma were reviewed. PET-CT findings were correlated with thyroglobulin levels, and histological, clinical and radiological follow-up.

RESULTS

58 rTSH PET-CT scans were performed in 47 patients with a previous thyroidectomy and radioiodine ablation. The only indication for PET-CT was a raised thyroglobulin level in 46 of 58 scans, with the remainder for characterisation of equivocal radiology or staging. 25 (43%) of PET-CT scans were positive for recurrent disease. Histological correlation was available for 21 (36%) scans. The overall sensitivity, specificity, positive predictive value and negative predictive value were 69%, 76%, 72% and 73%, respectively. Median unstimulated thyroglobulin in true-positive scans was 33 µg l(-1) and 2.2 µg l(-1) in the remainder (p=0.12). 4 of 35 (11%) patients with unstimulated thyroglobulin levels <10 µg l(-1) had true-positive scans. Median stimulated thyroglobulin in true-positive scans was 320 µg l(-1), and 10 µg l(-1) in the remainder (p=0.046), with no positive scans with a stimulated thyroglobulin <8 µg l(-1). PET-CT directly influenced patient management in 17/58 (29%) scans.

CONCLUSION

rTSH PET-CT is a useful imaging technique for detecting disease recurrence in patients with iodine-resistant differentiated thyroid cancer. Low stimulated thyroglobulin levels are potentially useful in identifying patients unlikely to benefit from a PET-CT scan.

BRAF mutation in papillary thyroid cancer and its value in tailoring initial treatment: a systematic review and meta-analysis

Clinicians have long sought to characterize biological markers of neoplasia as objective indicators of tumor presence, pathogenicity, and prognosis. Armed with data that correlate biomarker activity with disease presence and progression, clinicians can develop treatment strategies that address risks of disease recurrence or persistence and progression. The B-type Raf kinase (BRAF V600E) mutation in exon 15 of the BRAF gene has been noted to be a putative prognostic marker of the most prevalent form of thyroid cancer, papillary thyroid cancer (PTC)--a tumor type with high proclivity for recurrence or persistence. There has been a remarkable interest in determining the association of BRAF mutation with PTC recurrence or persistence. Using many new studies that have been published recently, we performed a meta-analysis to investigate correlations of BRAF mutation status with PTC prognosis, focusing on the recurrence or persistence of the disease after initial treatment. The study was based on published studies included in the PubMed and Embase databases addressing the BRAF mutation and the frequency of recurrence of PTC. We selected studies with data that enabled measurement of the risk ratio for recurrent disease. We also analyzed the factors that are classically known to be associated with recurrence. These factors included lymph node metastasis, extrathyroidal extension, distant metastasis, and American Joint Committee on Cancer (AJCC) stages III/IV. We used 14 articles that included an analysis of these factors as well as PTC recurrence data, with a total of 2470 patients from 9 different countries. The overall prevalence of the BRAF mutation was 45%. The risk ratios in BRAF mutation-positive patients were 1.93 (95% confidence interval [CI], 1.61-2.32; Z = 7.01; p < 0.00001) for PTC recurrence, 1.32 (95% CI, 1.20-1.45; Z = 5.73; p < 0.00001) for lymph node metastasis, 1.71 (95% CI, 1.50-1.94; Z = 8.09; p < 0.00001) for extrathyroidal extension, 0.95 (95% CI, 0.63-1.44; Z = 0.23; p = 0.82) for distant metastasis, and 1.70 (95% CI, 1.45-1.99; Z = 6.46; p < 0.00001) for advanced stage AJCC III/IV. Thus, in this meta-analysis, the BRAF mutation in PTC was significantly associated with PTC recurrence, lymph node metastasis, extrathyroidal extension, and advanced stage AJCC III/IV. Patients with PTC harboring mutated BRAF are likely to demonstrate factors that are associated with an increased risk for recurrence of the disease, offering new prospects for optimizing and tailoring initial treatment strategies to prevent recurrence.

Effectiveness of [(124)I]-PET/CT and [(18)F]-FDG-PET/CT for localizing recurrence in patients with differentiated thyroid carcinoma

Although the prognosis of patients with differentiated thyroid carcinoma (DTC) is generally encouraging, a diagnostic dilemma is posed when an increasing level of serum thyroglobulin (Tg) is noted, without detection of a recurrent tumor using conventional imaging tools such as the iodine-131 whole-body scanning (the [(131)I] scan) or neck ultrasonography (US). The objective of the present study was to evaluate the diagnostic value of [(124)I]-PET/CT and [(18)F]-FDG-PET/CT in terms of accurate detection of both iodine- and non-iodine-avid recurrence, compared with that of conventional imaging such as the [(131)I] scan or neck ultrasonography (US). Between July 2009 and June 2010, we prospectively studied 19 DTC patients with elevated thyroglobulin levels but who do not show pathological lesions when conventional imaging modalities are used. All involved patients had undergone total thyroidectomy and radioiodine (RI) treatment, and who had been followed-up for a mean of 13 months (range, 6-21 months) after the last RI session. Combined [(18)F]-FDG-PET/CT and [(124)I]-PET/CT data were evaluated for detecting recurrent DTC lesions in study patients and compared with those of other radiological and/or cytological investigations. Nine of 19 patients (47.4%) showed pathological [(18)F]-FDG (5/19, 26.3%) or [(124)I]-PET (4/19, 21.1%) uptake, and were classed as true-positives. Among such patients, disease management was modified in six (66.7%) and disease was restaged in seven (77.8%). In particular, the use of the described imaging combination optimized planning of surgical resection to deal with locoregional recurrence in 21.1% (4/19) of patients, who were shown to be disease-free during follow-up after surgery. Our results indicate that combination of [(18)F]-FDG-PET/CT and [(124)I]-PET/CT affords a valuable diagnostic method that can be used to make therapeutic decisions in patients with DTC who are tumor-free on conventional imaging studies but who have high Tg levels.

Glucose transporter 1 expression, tumor proliferation, and iodine/glucose uptake in thyroid cancer with emphasis on poorly differentiated thyroid carcinoma

PURPOSE

Glucose transporters 1 (GLUT1) facilitates glucose uptake in cancer. An inverse relationship between I-131 and F-18 fluorodeoxyglucose (FDG) uptake in PET/CT ("flip-flop phenomenon") was described for thyroid cancers (TCs) during dedifferentiation. We investigated the relationship among GLUT1 expression, proliferation, iodine concentration, and glucose uptake in different TC types, with emphasis on "poorly differentiated thyroid carcinoma" (PDTC).

METHODS

For immunohistochemistry, 95 thyroid tumors (follicular adenoma, papillary TC, follicular TC, PDTC, and anaplastic TC [ATC]) were investigated for GLUT1 expression and proliferation (Ki-67 index). For PET/CT study, 47 F-18 FDG PET/CT of patients with TC (22 PDTC), 39 corresponding I-124 PET/CT, and glucose and iodine uptake were evaluated. PTC and FTC were summarized under differentiated TC (DTC).

RESULTS

Immunohistochemistry: 65% of TC expressed GLUT1. The number of GLUT1-positive TC and GLUT1 expression increased with escalating dedifferentiation/aggressiveness of TC types (P < 0.001). A correlation between proliferation and GLUT1 expression was noted (P < 0.001). PET/CT study: F-18 FDG uptake was measured in 81% of cases. Occurrence of F-18 FDG-avid cases as well as median F-18 FDG maximum standardized uptake values were lowest in DTC, intermediate in PDTC, and highest in ATC. Accordingly, numbers of iodine-avid cases and median I-124 maximum standardized uptake value featured an inverse pattern.

CONCLUSIONS

Dedifferentiation in TC is accompanied by GLUT1 upregulation and increased proliferation. PDTC was found to be intermediate between DTC and ATC in terms of GLUT1 expression and F-18 FDG or I-124 uptake, suggesting that the flip-flop phenomenon occurs at a dedifferentiation stage in between. Furthermore, the results suggest that F-18 FDG PET/CT is an important imaging modality for ATC and PDTC.

Role of [(18)F]-fluorodeoxy-D-glucose positron emission tomography and computed tomography in the early detection of persistent/recurrent thyroid carcinoma in intermediate-to-high risk patients following initial radioactive iodine ablation therapy

BACKGROUND

Positron emission tomography/computed tomography (PET/CT) scan has a role in the surveillance of patients with a history of thyroid carcinoma. Its efficacy after remnant ablation as far as detecting persistent or recurrent thyroid carcinoma before other surveillance methods is not known, however. In intermediate-to-high risk thyroid carcinoma patients we studied whether PET/CT scan, performed 6-12 months after the first remnant ablation, could provide more information than ultrasonography (US) and thyrotropin-stimulated serum thyroglobulin (Tg) determination with diagnostic whole-body scan (DxWBS).

METHODS

We studied 71 subjects with differentiated thyroid cancer (DTC) who were intermediate-to-high risk for persistent/recurrent disease and who had received PET/CT scan, US, and DxWBS simultaneously with stimulated Tg levels 6-12 months after remnant ablation. To evaluate the diagnostic efficacy of PET/CT scan, the sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy were calculated.

RESULTS

Ten subjects (14%) had persistent/recurrent disease detected 6-12 months after remnant ablation. Persistence/recurrence was detected in nine (12.7%) of these patients by conventional methods, including US and DxWBS, along with stimulated Tg levels. The remaining case was detected solely by a PET/CT scan, which showed a mediastinal prevascular lesion; this was confirmed by a therapeutic WBS after additional radioiodine therapy. Among the six patients whose PET/CT scan showed positive results, five had persistent/recurrent disease. The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of PET/CT scan for detecting persistent/recurrent thyroid carcinoma were 50%, 98.4%, 83.3%, 92.3%, and 91.5%, respectively.

CONCLUSION

In intermediate-to-high risk patients with DTC seen 6-12 months after their first remnant ablation, there is almost no complementary role for adding a PET/CT scan to conventional follow-up methods, an US and a DxWBS simultaneously with stimulated Tg levels.

Positron emission tomography/computed tomography in patients treated for differentiated thyroid carcinomas

Differentiated thyroid cancer (DTC) generally has a favorable prognosis; however, the chance of a recurrence in patients with DTC is 20%, and 8% of patients with recurrence will subsequently die of the disease. After thyroid remnant ablation, detectable serum thyroglobulin levels are a sensitive marker for residual or recurrent disease, while imaging procedures, primarily neck ultrasound and an iodine-131 (¹³¹I) or iodine-123 diagnostic whole-body scan, are useful to localize recurrent disease. However, ultrasound cannot identify lesions outside the neck, and diagnostic whole-body scan is of limited value if progressive dedifferentiation of thyroid carcinoma cells occurs. In these patients, fluorine-18 (¹⁸F)-fluorodeoxyglucose PET/computed tomography (¹⁸FDG-PET/CT) has been shown to improve detection and localization of tumor foci. Additionally, ¹⁸FDG-PET/CT is also of value in selecting patients unlikely to benefit from additional ¹³¹I therapy and those at highest risk of disease-specific mortality, which may prompt more alternative therapies. Recently, iodine-124 (¹²⁴I)-PET/CT was proved to perform better than low-dose diagnostic ¹³¹I scans. Additionally, ¹²⁴I PET/CT succesfully predicts the results of subsequent high-dose post-treatment ¹³¹I scans and allows lesion-based dosimetric calculations. The present article reviews the utility and limitations of PET/CT techniques in DTC management and offers practical recommendations.

PET-CT scans in recurrent or persistent differentiated thyroid cancer: is there added utility beyond conventional imaging?

BACKGROUND

Integrated positron emission tomography (PET)-computed tomography (CT) may have advantages over conventional imaging in localizing recurrent or persistent differentiated thyroid cancer.

METHODS

A retrospective review of patients who underwent PET-CT scans was performed. Results were compared with contrast CT, magnetic resonance imaging, ultrasonography, and radioactive iodine (RAI) scans.

RESULTS

Thirty patients (mean age, 49.9 ± 17 years) underwent 36 PET-CT scans, mostly for elevated thyroglobulin levels and negative RAI scans (30 scans). Fifty percent (18/36) of PET-CT scans showed increased uptake in the neck, 11 of 36 (31%) in the chest, 3 of 36 (8.3%) in bone, and 6 of 36 (16.6%) in other areas. PET-CT had overall sensitivity, specificity, and positive predictive values of 73.9%, 61.5%, and 77.3% respectively. To assess the added value of PET-CT, we focused on the 21 scans performed after conventional imaging in 20 patients. PET-CT provided additional information in 2 (10%) patients, both of whom were spared interventions. However, PET-CT underestimated extent of disease in 3 (15%) patients and led to unnecessary interventions in 3 (15%) additional patients.

CONCLUSION

PET-CT has reasonable sensitivity in the detection of recurrent thyroid cancer. However, the added value of PET-CT may be seen only in a limited number of patients after good quality, conventional imaging. Further studies are needed to determine the most cost-effective approach to managing these patients.

18F-FDG PET/CT imaging in oncology

Accurate diagnosis and staging are essential for the optimal management of cancer patients. Positron emission tomography with 2-deoxy-2-[fluorine-18]fluoro-D-glucose integrated with computed tomography (18F-FDG PET/CT) has emerged as a powerful imaging tool for the detection of various cancers. The combined acquisition of PET and CT has synergistic advantages over PET or CT alone and minimizes their individual limitations. It is a valuable tool for staging and restaging of some tumors and has an important role in the detection of recurrence in asymptomatic patients with rising tumor marker levels and patients with negative or equivocal findings on conventional imaging techniques. It also allows for monitoring response to therapy and permitting timely modification of therapeutic regimens. In about 27% of the patients, the course of management is changed. This review provides guidance for oncologists/radiotherapists and clinical and surgical specialists on the use of 18F-FDG PET/CT in oncology.

PET and PET/CT in the management of thyroid cancer

The introduction of PET(-CT) has brought about a major paradigm shift in the management of thyroid carcinoma, especially from the diagnostic standpoint. From the viewpoint of patient management, the areas where it has made significant impact include the following: (1) the detection of disease focus in patients with differentiated thyroid carcinoma with elevated Tg levels and negative radioiodine scan. When localized disease is identified with F-18 FDG-PET-CT, surgery or focused radiotherapy could be utilized to eradicate the tumor; (2) the localization of disease in patients of MTC with elevated serum calcitonin levels; (3) the detection of unsuspected focal F-18 FDG uptake in the thyroid in patients undergoing whole body F-18 FDG PET for a different indication. This would prompt a workup to rule out thyroid carcinoma. The use of I-124 is evolving at this time and has been of great promise with regard to (a) its better efficacy of lesion detection and (b) the ability to provide lesion-specific dosimetry. In addition, F-18 FDG PET appears to be of potential value in patients with thyroid lymphoma in making the initial diagnosis, monitoring therapeutic response, and assessing for residual disease and/or recurrence.

Phase II study of daily sunitinib in FDG-PET-positive, iodine-refractory differentiated thyroid cancer and metastatic medullary carcinoma of the thyroid with functional imaging correlation

PURPOSE

We conducted a phase II study to assess the efficacy of continuous dosing of sunitinib in patients with flurodeoxyglucose positron emission tomography (FDG-PET)-avid, iodine-refractory well-differentiated thyroid carcinoma (WDTC) and medullary thyroid cancer (MTC) and to assess for early response per FDG-PET.

EXPERIMENTAL DESIGN

Patients had metastatic, iodine-refractory WDTC or MTC with FDG-PET-avid disease. Sunitinib was administered at 37.5 mg daily on a continuous basis. The primary end point was response rate per Response Evaluation Criteria in Solid Tumors (RECIST). Secondary end points included toxicity, overall survival, and time to progression. We conducted an exploratory analysis of FDG-PET response after 7 days of treatment.

RESULTS

Thirty-five patients were enrolled (7 MTC, 28 WDTC), and 33 patients were evaluable for disease response. The primary end point, objective response rate per RECIST, was 11 patients (31%; 95% confidence interval, 16-47%). There were 1 complete response (3%), 10 partial responses (28%), and 16 patients (46%) with stable disease. Progressive disease was seen in 6 patients (17%). The median time to progression was 12.8 months (95% confidence interval, 8.9 months-not reached). Repeat FDG-PET was done on 22 patients. The median percent change in average standardized uptake values was -11.7%, -13.9%, and 8.6% for patients with RECIST response, stable disease, and progressive disease, respectively. Differences between response categories were statistically significant (P = 0.03). The most common toxicities seen included fatigue (11%), neutropenia (34%), hand/foot syndrome (17%), diarrhea (17%), and leukopenia (31%). One patient on anticoagulation died of gastrointestinal bleeding.

CONCLUSION

Continuous administration of sunitinib was effective in patients with iodine-refractory WDTC and MTC. Further study is warranted.

Does recombinant human thyrotropin-stimulated positron emission tomography with [18F]fluoro-2-deoxy-D-glucose improve detection of recurrence of well-differentiated thyroid carcinoma in patients with low serum thyroglobulin?

BACKGROUND

Thyrotropin (TSH) stimulates thyrocyte metabolism, glucose transport, and glycolysis. The interest in using recombinant human TSH (rhTSH) stimulation of fluoro-2-deoxy-D-glucose (FDG) with positron emission tomography (PET) has been shown, but mainly for patients with high serum thyroglobulin (Tg) concentration. We evaluated the use of rhTSH-stimulated PET-FDG in patients with low serum Tg concentration.

METHODS

Sixty-one PET/computed tomography (CT)-FDG (Biograph Sensation 16; Siemens Medical Solutions, Knoxville, TN) were performed in 44 patients (28 women and 16 men; 51 +/- 16 years) with positive Tg levels, negative or no contributive iodine-131 whole-body scintigraphy results, and no contributive morphological imaging results (ultrasound, magnetic resonance imaging, and CT). Thirty-eight patients had papillary carcinoma and six had follicular thyroid carcinoma. All patients had previously undergone total thyroidectomy and postoperative iodine ablation of thyroid bed remnant tissue. The rhTSH-stimulated PET/CT-FDG (5 MBq/kg) was performed after two 0.9 mg intramuscular doses of rhTSH (Thyrogen; Genzyme) which were administered 48 and 24 hours before imaging, while patients continued levothyroxine (LT(4)). Blood sampling was performed immediately before FDG injection for measurement of serum TSH and Tg concentrations (TSH(1) and Tg(1)) and after 48 hours (TSH(2) and Tg(2)). PET/CT-FDG findings were compared with the Tg: (i) at the initial iodine treatment during T(4) withdrawal (Tg(ini)), (ii) under T(4) (Tg(T4)) within 3 months before the PET/CT-FDG, (iii) with Tg(1), and (iv) with Tg(2). PET/CT-FDG findings were correlated with the findings of histology, iodine-131 whole-body scintigraphy, morphological imaging, or clinical follow-up.

RESULTS

The mean Tg(ini) was 785 +/- 2707 microg/L for a TSH of 73 +/- 64 mU/L. The mean Tg(T4) was 7 +/- 15 microg/L (T(4) = 195 +/- 59 microg/day; mean TSH of 0.24 +/- 0.57 mU/L). Among the 44 patients, PET/CT-FDG findings were positive in 20 and negative in 24. Among the 61 PET/CT-FDG, 25 PET/CT-FDG were positive (41%). Among the 25 positive PET, the Tg(T4) values were less than 10 microg/L for 19, including 9 true-positive patients (20% of the 44 patients). There was no difference of PET/CT-FDG results (positive vs. negative) as related to the serum Tg concentrations (p = 0.99 for Tg(ini), p = 0.95 for Tg(T4), p = 0.07 for Tg(1), and p = 0.42 for Tg(2)). No relation was observed with PET/CT-FDG results and initial tumor size (p = 0.52) or node metastasis (p = 0.14).

CONCLUSION

In the diagnosis of recurrent disease in patients with differentiated thyroid carcinoma and low Tg level, the sensitivity of rhTSH-stimulated PET/CT-FDG seems to be low and no correlation was observed between PET/CT-FDG findings and Tg level. However, positive PET-FDG results have been found in 9/44 (20%) patients with serum Tg levels lower than 10 microg/L. Therefore, this series shows that a cutoff value of 10 microg/L for the Tg under T(4) is probably not the best criteria to select patient candidates for PET/CT-FDG examination to detect the recurrence of differentiated thyroid carcinoma.

The value of positron emission tomography (PET) in the management of patients with thyroid cancer

For more than a decade, positron emission tomography (PET) has had an important role in the management of thyroid cancer patients. It may be involved in initial, sometimes inadvertent, diagnosis; in postoperative evaluation; in detection of occult metastases; in the evaluation of thyroid nodules; and in prognostication of metastatic disease. In this review we will update the advances in the application of PET scanning to optimal patient management. The majority of the published studies to date have used 18F-fluoro-deoxyglucose (FDG) as the PET isotope, and unless specifically noted, all references to PET scanning will imply that this tracer has been used.

Current role of radionuclide imaging in differentiated thyroid cancer

Nuclear medicine plays an integral role in the management of differentiated thyroid cancer. This editorial aims to provide a summary of the current role of radionuclide imaging, including whole body iodine scan and fluorodeoxyglucose (FDG)-positron emission tomography (PET), in the diagnostic work-up and follow-up of patients with thyroid cancer.