Compare FDG-PET and Tc-99m tetrofosmin SPECT to detect metastatic thyroid carcinoma

Positron Emission Tomography (PET) and PET/CT in Thyroid Cancer: A Systematic Review and Meta-Analysis

BACKGROUND

Positron emission tomography (PET) and PET/CT are functional imaging methods that are widely used in diagnostic procedures in oncology.

OBJECTIVES

The objective of this study was to assess the patient-relevant benefit of PET or PET/CT in patients with thyroid cancer based on a literature review and meta-analysis.

METHODS

A systematic review including studies that had been published until December 2013 was performed. To be included, studies had to prospectively investigate patients with thyroid cancer in a clinical setting of staging, restaging, or diagnosing tumour recurrence.

RESULTS

Out of 3,506 potentially relevant articles, 29 studies were included. No study directly evaluated the benefits of PET. Twenty-eight studies dealt with the diagnostic accuracy of PET or PET/CT, and 1 study evaluated the prognostic value of PET/CT. The authors showed that a positive result of PET/CT in restaging patients with differentiated thyroid cancer yielded a significant decrease in overall survival (hazard ratio, HR 5.01, CI 3.41-6.62). In patients with suspected recurrence of differentiated thyroid cancer, meta-analysis showed higher sensitivity of PET (89.7%, CI 78-99%) and PET/CT (94.3%, CI 87-97%) compared with conventional imaging (65.4%, CI 32-88%) and comparable results for specificity. Due to the low numbers of studies and patients, meta-analyses on medullary carcinoma did not produce meaningful results.

CONCLUSION

The patient-relevant benefits of PET or PET/CT in thyroid cancer could not be evaluated satisfactorily based on the included studies. It remains unclear whether higher diagnostic test accuracy leads to changes in therapeutic strategies and better patient-relevant outcomes.

A comprehensive overview of radioguided surgery using gamma detection probe technology

The concept of radioguided surgery, which was first developed some 60 years ago, involves the use of a radiation detection probe system for the intraoperative detection of radionuclides. The use of gamma detection probe technology in radioguided surgery has tremendously expanded and has evolved into what is now considered an established discipline within the practice of surgery, revolutionizing the surgical management of many malignancies, including breast cancer, melanoma, and colorectal cancer, as well as the surgical management of parathyroid disease. The impact of radioguided surgery on the surgical management of cancer patients includes providing vital and real-time information to the surgeon regarding the location and extent of disease, as well as regarding the assessment of surgical resection margins. Additionally, it has allowed the surgeon to minimize the surgical invasiveness of many diagnostic and therapeutic procedures, while still maintaining maximum benefit to the cancer patient. In the current review, we have attempted to comprehensively evaluate the history, technical aspects, and clinical applications of radioguided surgery using gamma detection probe technology.

Utility of fluorodeoxyglucose-PET in patients with differentiated thyroid carcinoma

AIM

In differentiated thyroid carcinoma, persistent plasma thyroglobulin (Tg) is a specific marker for persistent or recurrent disease after thyroidectomy and radioiodine ablation. When Tg remains elevated and no substrate can be found on whole-body radioiodine imaging (131I-WBS), or even when recurrent disease is suspected with normal Tg, conventional imaging (CI) is often insufficient. As fluorodeoxyglucose (FDG)-PET has proven to be an effective modality for detecting various types of cancer, the utility of FDG-PET was analysed and compared with CI in this retrospective study in patients with differentiated thyroid cancer.

PATIENTS AND METHODS

After total thyroidectomy and radioiodine ablation, 68 FDG-PET scans were performed in 39 patients with elevated Tg levels or clinical suspicion of recurrent disease. At the time of FDG-PET, 54 131I-WBS (in 30 patients) were negative, 14 (in 11 patients) were equivocal. Tg was normal at the time of 14 scans (10 patients) and elevated in 54 (in 33 patients). FDG-PET results were compared with histology, 131I-WBS and CI and clinical follow-up. Sensitivity and specificity were evaluated in various subgroups.

RESULTS

Overall, there were 35 true-positive, two false-positive, 20 true-negative and three false-negative FDG-PET scans. In six of these cases (one true positive, five true negative) FDG-PET was repeated without intervention and in an additional eight FDG-PET scans no definite conformation of abnormal FDG-PET could be obtained, so these results were not used for statistical analysis. Sensitivity, specificity, PPV and NPV for the whole group were 92, 88, 94 and 83%, respectively. In 38 scans performed on 31 patients with elevated Tg levels, who were not known with recurrence, this was 84, 100, 100 and 75%, respectively. In 16 scans in 10 patients with known recurrence (all with elevated Tg), sensitivity and PPV were 100% without false-positive or false-negative results. When Tg was not detectable (14 scans in 10 patients), sensitivity, specificity, PPV and NPV were 100, 75, 60 and 100%, respectively. After 35 FDG-PET scans (51%), there was a change in patient management by avoiding ineffective 131I treatment, by guiding surgical reintervention, or avoiding futile surgery. One FP FDG-PET resulted in an unnecessary surgical procedure. In 33 cases, FDG-PET did not lead to a change in treatment policy, which retrospectively would have been beneficial in six cases.

CONCLUSION

FDG-PET affected patient management in patients with differentiated thyroid cancer and negative 131I-WBS, not only when Tg is elevated, but also when Tg is not detectable and therefore the use of FDG-PET as a diagnostic tool is justified in these patients.

99mTc-sestamibi radio-guided surgery of loco-regional 131Iodine-negative recurrent thyroid cancer

AIM

We report here our experience in a larger series of differentiated thyroid cancer (DTC) patients who had been treated by (99m)Tc-sestamibi radio-guided surgery (RGS) for (131)Iodine ((131)I)-negative loco-regional recurrent disease.

METHODS

Fifty-eight patients with loco-regional (131)I-negative recurrent disease from DTC were studied with (99m)Tc-sestamibi directed RGS using a hand-held 11-mm gamma probe as an intra-operative detector. Patients were selected for RGS on the basis of (a) progressive increase of serum thyroglobulin (Tg) levels after first treatment during follow-up, (b) negative high dose (100 mCi, 3.7 GBq) (131)I whole-body scan, and (c) positive pre-operative (99m)Tc-sestamibi scintigraphy for the presence of loco-regional recurrent disease. There were 41 papillary (1 "tall" cell variant), 13 follicular and 4 Hürthle cells tumours. In 14 patients thyroid cancer recurred in the thyroid bed while cervical lymph node metastases were found in 37 patients, and 7 patients had recurrent disease both in the thyroid bed and in cervical lymph nodes.

RESULTS

At bilateral neck exploration, 147 metastatic foci ranging from 4 mm to 51 mm in largest diameter (mean tumour diameter=17.3+/-9.5mm) were removed. Eighty-five of them (58%) had been pre-operatively identified at (99m)Tc-sestamibi scintigraphy. After RGS, serum Tg levels normalised in 43 of 58 patients (serum Tg<2 ng/ml--they were considered disease-free), serum Tg remained slightly increased in 12 patients without evidence of metastatic disease at scintigraphic and radiologic imaging (serum Tg<10 ng/mg--they were considered living with microscopic disease), while serum Tg significantly increased up to values>900 ng/ml in 3 patients who developed lung metastases. The mean lesion to background (99m)Tc-sestamibi uptake ratios decreased in all 58 patients (p<0.0001). Post-surgical follow-up ranged 6-72 months (mean+/-SD=29.6+/-13.5 months). The operating surgeon assessed RGS as very useful in 14 patients in whom metastatic foci were embedded in fibrotic tissues or located behind blood vessels, useful in 22 patients, moderately useful 17 patients and not useful in 5 patients.

CONCLUSION

Our data suggest that a (99m)Tc-sestamibi intra-operative gamma probe can be used to identify and guide resection of recurrent loco-regional tumour in DTC patients with (131)I-negative loco-regional metastatic foci.

Utilidade da tomografia de emissão de pósitrons com fluoro-deoxiglicose (FDG-PET) na avaliação do câncer de tireóide: uma revisão sistemática

Após o tratamento inicial do câncer tireoidiano, a detecção de prováveis recorrências e/ou metástases se faz através da dosagem de marcadores séricos e estudos de imagem. Essas técnicas podem ser negativas apesar de evidências bioquímicas de doença metastática. A tomografia de emissão de pósitrons com fluorodeoxiglicose (FDG-PET) tem sido proposta como um teste acurado para detectá-la. O objetivo deste estudo é apresentar uma síntese das evidências obtidas através de revisão sistemática sobre a acurácia do FDG-PET na localização de metástases de câncer tireoidiano previamente tratado, nos quais as modalidades convencionais falharam na sua detecção. Foi realizada uma pesquisa bibliográfica no MEDLINE de todos os trabalhos relativos a FDG-PET e carcinoma tireoidiano diferenciado, indexados até setembro de 2005. Foram obtidas 216 citações e 17 trabalhos foram incluídos, 71% publicados a partir de 2000. A sensibilidade da FDG-PET foi elevada, com apenas um trabalho apresentando sensibilidade inferior a 75%. A especificidade, examinada em 12 estudos, foi menor que 75% em 3 estudos. Em 41% dos trabalhos existia pelo menos um teste comparativo com o FDG-PET. Os resultados apontam o FDG-PET como um teste diagnóstico útil para a detecção e localização de metástases do câncer tireoidiano, com implicações diretas no tratamento dos pacientes.

Radio-guided surgery for non-131I-avid thyroid cancer

OBJECTIVE

In this paper we report in a larger series the use of radio-probe-guided surgery (RGS) in nonradioiodine avid, well-differentiated thyroid cancer (DTC).

DESIGN

Thirty-seven patients with locoregional recurrent, nonradioiodine avid DTC were studied with (99m)Tc-sestamibi directed RGS using a handheld gamma probe as an intraoperative detector.

OUTCOME

Twenty-three women and 14 men were followed after RGS for 35.4 +/- 12.5 months (range 9-57). There were 33 papillary (one "tall" cell variant), 2 follicular, and 2 Hürthle cell cancers. In 7 patients, thyroid cancer recurred in the neck while cervical lymph node metastases were found in 31 patients (one patient had papillary cancer in both the thyroid bed and cervical lymph nodes). Sixty-six discrete nodules ranging from 6 to 45mm (mean tumor diameter, 18.4 +/- 8.5mm) were identified by both high-resolution ultrasound and (99m)Tc-sestamibi probe-guided RGS. After RGS, Tg (thyroglobulin) fell in 33 of 37 patients and mean target=nontarget sestamibi uptake ratios decreased in all 37 patients ( p < 0.0001).

CONCLUSION

These data confirm our earlier observations that a (99m)Tc-sestamibi intraoperative gamma probe can be used to identify and guide resection of recurrent tumor and involved lymph nodes in locoregional metastases of nonradioiodine-avid thyroid cancer.

FDG-PET Detected Thyroid Incidentalomas: Need for Further Investigation?

BACKGROUND

Incidental thyroid abnormalities are increasingly detected in patients undergoing PET scans. The aim of this study was to review our experience with the management of PET detected thyroid incidentalomas in a large single institution series.

METHODS

All PET scans performed from May 2003 to July 2005 were reviewed and patients with incidental thyroid abnormalities were identified. From this group, patients that underwent further investigation were analyzed. Data relating to PET scan findings, FNA diagnoses, operative details, and histopathology was reviewed.

RESULTS

In 8,800 patients, 16,300 PET scans were performed of whom 263 patients (2.9% of patients and 1.6% of PET scans) had findings positive for thyroid abnormality. Thyroid malignancy was noted in 42% (24 patients) of the 57 patients that underwent FNA. In the group of 27 patients that were subjected to operative intervention, 74% (20 patients) were noted to have a malignant diagnosis. The final histopathology revealed primary thyroid carcinoma in all these 20 patients (19 patients with papillary carcinoma and one patient with primary thyroid lymphoma). The factors that correlated with an increased risk of malignancy were the presence of physical finding (p = 0.01) and focal (p < 0.01) or unilateral uptake (p < 0.01) on PET scan. The average SUV was not useful in differentiating benign (9.2) from malignant lesions (8.2, p = 0.7).

CONCLUSIONS

PET detected incidental thyroid abnormalities are rare. In patients with positive PET scan findings and suspicious features, the incidence of primary thyroid malignancy is very high. These patients warrant further investigation followed by possible operative intervention.

Tc-99m depreotide imaging of I-131-negative recurrent metastatic papillary thyroid carcinoma

The detection of radioiodine (I-131)-negative metastases of differentiated thyroid carcinoma (DTC) has been hitherto successfully tried by the well-known synthetic somatostatin analogue indium-111-labeled DTPA-octreotide (In-111 pentetreotide). The objective of this study was to evaluate the usefulness of scintiscan with the newer synthetic somatostatin analogue Tc-99m depreotide, in the restaging of papillary thyroid carcinoma (PTC) with detectable serum thyroglobulin (Tg) levels and negative I-131 whole-body scan (WBS). Whole-body planar and cervico-thoracic tomographic scintigraphy (single-photon emission tomography-SPET) with Tc-99m depreotide was performed in a 68-year-old male patient suffering from PTC stage III, with a mild increase in serum Tg levels coupled with a recent negative I-131 WBS. The findings were compared with those of neck ultrasonography (US) and computerized tomography (CT). Nodal neck dissection and histopathology provided the definitive diagnosis. Tc-99m depreotide scanning revealed foci of cervical lymph node metastases, which did not accumulate I-131. The findings were in accordance with neck US and CT. Histopathology established the diagnosis of metastatic cervical lymph node PTC. Lymph node immunoreactivity was positive for the somatostatin receptor subtypes 2, 5 and 3. Scintigraphy with Tc-99m depreotide could prove a useful adjunct to the armamentarium for the follow-up of PTC, especially in the setting of detectable serum Tg and negative I-131 WBS.

Value of 111In-DOTA-lanreotide and 111In-DOTA-DPhe1-Tyr3-octreotide in differentiated thyroid cancer: results of in vitro binding studies and in vivo comparison with 18F-FDG PET

PURPOSE

Radioiodine-negative thyroid cancer presents diagnostic and therapeutic difficulties, warranting the implementation of new imaging and treatment strategies. The purpose of this study was twofold. First, we investigated in vitro the binding characteristics of 111In-DOTA-lanreotide (111In-DOTA-LAN) and 111In-DOTA-D: Phe1-Tyr3-octreotide (111In-DOTA-TOC) to cells derived from differentiated thyroid cancer (DTC). Second, we evaluated the value of somatostatin receptor (SSTR) scintigraphy with these radioligands, as compared with 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET), for the detection of tumour lesions in DTC patients.

METHODS

Binding of 111In-DOTA-LAN and 111In-DOTA-TOC to cells isolated from surgically removed thyroid tissue was evaluated in vitro by performing saturation and displacement studies. Eighteen DTC patients with elevated thyroglobulin (12 radioiodine-negative, six radioiodine-positive) were investigated with 111In-DOTA-LAN, 111In-DOTA-TOC and 18F-FDG PET scans.

RESULTS

Large numbers of SSTR binding sites for 111In-DOTA-LAN and 111In-DOTA-TOC were found on the cells investigated. Both SSTR radioligands exhibited a high binding affinity for these SSTR binding sites. 111In-DOTA-LAN and 111In-DOTA-TOC scintigraphy detected 37 and 33 lesions, respectively, in 17 (94%) patients each, whereas 18F-FDG PET revealed 30 lesions in 15 (83%) patients. Uptake of both SSTR radioligands was found in several radioiodine-negative sites. No striking differences in lesion imaging by 111In-DOTA-LAN and 111In-DOTA-TOC were found. In both radioiodine-negative and radioiodine-positive patients, more lesions were SSTR-positive/18F-FDG-negative than were 18F-FDG-positive/SSTR-negative.

CONCLUSION

Adding a SSTR scan with these radioligands to the diagnostic work-up increases the diagnostic capacity in DTC, and should be considered particularly in radioiodine-negative patients with elevated thyroglobulin levels.