In-111 DTPA-octreotide scintigraphy for disease detection in metastatic thyroid cancer: comparison with F-18 FDG positron emission tomography and extensive conventional radiographic imaging

The value of I-131 SPECT in the detection of recurrent differentiated thyroid cancer

AIM

The aim of this study is to assess the additional value of radioiodine-131 (I-131) single-photon emission computed tomography (SPECT) to whole-body scintigraphy (WBS) in the detection of recurrent differentiated thyroid cancer.

MATERIALS AND METHODS

Eighty-seven consecutive patients with differentiated thyroid cancer, who had undergone a diagnostic SPECT WBS study, were included. In all patients, posttreatment scans, computed tomography scanning or ultrasonography were used to assess positive results, whereas follow-up was used in patients with a negative scan result. General data, such as primary tumor, histology and biochemical parameters were also gathered.

RESULTS

In this study cohort, nine positive diagnostic WBS were found compared with 31 positive SPECT scans. In eight of the nine (89%) positive WBS, recurrent thyroid cancer was found at the same location on the SPECT scan. In 56 patients SPECT and WBS were negative. Moreover, eight patients with a positive SPECT study had a serum thyroglobulin level less than 1 microg/l, which, in our hospital, was the cut-off level for treatment. On the basis of the serum thyroglobulin measurements and the WBS, 9% of the patients would not have been treated.

CONCLUSION

I-131 SPECT of the head and neck region and chest has a complementary role for planar imaging in the follow-up of patients treated for differentiated thyroid cancer. Therefore, its use in addition to WBS is strongly recommended in clinical practice.

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.

Radionuclides in the management of thyroid cancer

Nuclear medicine imaging was born over 60 years ago with imaging of thyroid conditions. Most of our present imaging devices were developed for imaging of the thyroid and thyroid cancer. Millions of patients in over 100 countries have been diagnosed and treated for thyroid cancer using nuclear medicine techniques. It remains, however, one of the most dynamic areas of development in nuclear medicine with new roles for positron emission tomography and receptor based imaging. In addition to this is research into combinations of genetic therapy and radioisotopes and receptor based therapy using beta emitting analogues of somatostatin. Despite the use of ultrasound computed tomography and magnetic resonance, nuclear medicine techniques remain central to both imaging and therapy in thyroid disease and the field has recently become one of the most dynamic within the specialty.

PET imaging in differentiated thyroid cancer: where does it fit and how do we use it?

Positron emission tomography (PET) is a rapidly evolving imaging modality that has gained widespread acceptance in oncology, with several radionuclides applicable to thyroid cancer. Thyroid cancer patients have been studied most commonly using 18F-Fluorodeoxyglucose (FDG)-PET, with perhaps the greatest utility being the potential localization of tumor in differentiated thyroid cancer (DTC) patients who are radioiodine whole body scan (WBS) negative and thyroglobulin (Tg) positive. Also of value is the identification of patients unlikely to benefit from additional 131I therapy and identification of patients at highest risk of disease-specific mortality, which may prompt more aggressive therapy or enrollment in clinical trials. Emerging data suggest that PET/CT fusion studies provide increased accuracy and modify the treatment plan in a significant number of DTC cases when compared to PET images alone. However, studies documenting improvements in survival and tumor recurrence attributable to FDG-PET imaging in thyroid cancer patients are lacking. Specific case examples of thyroid cancer patients who appear to have benefited from FDG-PET imaging do exist, while less data are available in the setting of anaplastic or medullary thyroid carcinoma. This article reviews the utility and limitations of FDG-PET in DTC management, and offers practical recommendations.

Hürthle cell thyroid carcinoma metastatic to the sigmoid colon

Prognosis of differentiated thyroid cancer is favorable in the majority of cases. However, distant metastases occur in 10-15% of cases, predominantly in lungs and bones, especially in older patients exhibiting poorly differentiated forms or advanced stages. We report a case history of Hürthle cell thyroid carcinoma metastasized to the sigmoid colon. To the best of our knowledge, this location has never been described before. This case history illustrates the difficulties of diagnosis and treatment in patients whose metastases do not concentrate radioiodine. The interest of different imaging modalities, including fluoro-deoxy-glucose positron emission tomography scan and somatostatin receptor scintigraphy, is discussed.

Role Of [18F]Fluorodeoxyglucose Positron Emission Tomography In Follow-Up Of Differentiated Thyroid Cancer

OBJECTIVE

To assess the diagnostic utility of [(18)F]flu-orodeoxyglucose positron emission tomography (FDG PET) in the follow-up of patients with differentiated thyroid cancer (DTC).

METHODS

In this study, we used strict definitions of presence and absence of the disease and performed all FDG PET scans while the patients were not taking levothyroxine (LT4). We report the results of conventional FDG PET scans obtained during the follow-up of 50 nonselected patients with DTC (34 female and 16 male patients; median age, 40.5 years; range, 18 to 68). All FDG PET scans and measurement of thyroglobulin (Tg) levels were performed while the patients were not taking LT4 (thyrotropin>or=25 microIU/mL). Tg antibodies were negative in all patients. The initial surgical procedure was total thyroidectomy in all cases, and 26 patients underwent additional operations (2 to 4 procedures). Radioactive iodine (131I) therapy was given to 48 patients (median dose, 5,550 MBq). In 42 patients, FDG PET was used for evaluation of Tg-positive (Tg>2 ng/mL in the absence of LT4 therapy), scan-negative disease. In 8 patients, Tg was <or=2 ng/mL but other findings suggested the presence of the disease (detectable Tg in 7 cases and abnormal ultrasound findings in 3). Disease was considered present if confirmed by fine-needle aspiration, histopathologic examination of subsequent surgical specimens, or persistent elevation of Tg levels (>2 ng/mL without LT4 therapy) for >1 year. Disease was considered absent if Tg was <or=2 ng/mL and at least all the following imaging studies were negative: diagnostic radioiodine whole-body scan, chest radiography or spiral computed tomography of the chest, and high-resolution neck ultrasonography. If all these criteria were present, a positive FDG PET scan was considered a false-positive study.

RESULTS

FDG PET scans were positive in 27 patients (54%) and negative in 23 (46%). FDG PET results were true-positive in 26 cases, false-positive in 1, true-negative in 7, and false-negative in 16. The sensitivity, specificity, and positive and negative predictive values were 61.9%, 87.5%, 96.3%, and 30.4%, respectively.

CONCLUSION

FDG PET scanning is moderately sensitive and specific for detection of persistent or recurrent DTC.

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.