Negative 131I Scan Research Articles

The role of Tg kinetics in predicting 2-[18F]-FDG PET/CT results and overall survival in patients affected by differentiated thyroid carcinoma with detectable Tg and negative 131I-scan

PurposeThe aim of this study was to assess the potential role of thyroglobulin (Tg) kinetics in predicting 2-[18F]-FDG-PET/CT results and overall survival (OS) in patients affected by differentiated thyroid carcinoma (DTC) and suspected recurrence.MethodsOn hundred and thirty-nine patients were retrospectively included. All patients underwent 2-[18F]-FDG-PET/CT due to detectable Tg levels and negative [131I] whole-body scan. The last two consecutive serum Tg measurements before PET/CT were used for Tg-doubling time (TgDT) and Tg-velocity (Tg-vel) calculation. Receiver operating characteristic (ROC) curves were used to determine the optimal cutoff points for Tg, TgDT and Tg-vel for predicting PET/CT results.ResultsOne hundred and fifteen (83%) patients had positive PET/CT for DTC recurrence, while the remaining 24 (17%) negative. Stimulated Tg before PET and Tg-vel were significantly higher in patients with a positive PET/CT scan than negative scan (average Tg 190 vs 14 ng/mL, p = 0.006; average Tg-vel 4.2 vs 1.7 ng/mL/y, p < 0.001). Instead, TgDT was significantly shorter in positive scan (average TgDT 1.4 vs 4.4 years, p < 0.001). ROC curve analysis revealed the best Tg, TgDT and Tg-vel cutoff of 18 ng/mL,1.36 years and 1.95 ng/mL/y. In patients with Tg<18 ng/mL, the PET/CT detection rate was significantly lower in patients with low Tg-vel (p = 0.018) and with long TgDT (p = 0.001). ATA class risk, PET/CT results and Tg before PET were confirmed to be independent prognostic variables for OS.ConclusionsTg kinetics may help to predict 2-[18F]-FDG-PET/CT results in DTC patients with negative [131I]WBS and detectable Tg, especially in case of low-moderate Tg.

Role of early 18F-FDG PET/CT in the management of differentiated thyroid cancer patients with negative 131I scan and elevated thyroglobulin levels

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Re-differentiation of radioiodine-refractory BRAF V600E-mutant thyroid carcinoma with dabrafenib: A pilot study.

6025 Background: Resistance to radioactive iodine is a leading cause of mortality in differentiated thyroid carcinoma. The MAPK pathway is a major determinant of iodine uptake into thyroid carcinoma cells. Mutations in BRAF activate this pathway, resulting in resistance to radioactive iodine. A pilot study using the MEK1/2 inhibitor, selumetinib, (Ho, ASCO 2012) increased radioiodine uptake in a subset of thyroid cancers. Methods: This is a single institution, single arm pilot study investigating the potential for the BRAF inhibitor dabrafenib to induce radioiodine uptake in metastatic, BRAF-mutant, radioiodine-refractory papillary thyroid carcinoma (PTC). The primary endpoint is increased radioiodine uptake demonstrated on a 4mCi 131-I whole body scan. Patients with increased uptake receive 14 additional days of dabrafenib followed by treatment with 150mCi 131-I. Secondary endpoints include safety and tolerability and clinical benefit as measured by decreases in serum thyroglobulin and objective response rate per modified RESIST 1.1. Results: To date, 7 patients have been enrolled. All had negative 131-I scans within 14 months of enrollment. No dose adjustments for toxicity have been needed. One patient developed reversible hypophosphatemia and a second developed a benign skin lesion. 3 of 5 evaluable patients developed radioiodine uptake after 28 days of dabrafenib, and new radioiodine-avid lesions were demonstrated in all three after receiving a therapeutic dose of 131-I. All three patients demonstrated increases in thyroglobulin levels during treatment with dabrafenib. Conclusions: This initial data suggests that a subset of patients with radioiodine-resistant BRAF-mutant PTC demonstrate new iodine uptake following treatment with dabrafenib. Reuptake may correlate with increases in thyroglobulin, suggestive of re-differentiation. It is not yet known whether increased uptake of radioactive iodine will translate into a radiographic response. Two patients failed to convert to radioiodine-sensitive disease; it is possible that BRAF inhibition was incomplete in these patients and/or determinants other than BRAF mutation status contribute to radioiodine sensitivity. Clinical trial information: NCT01534897.

Axillary Lymph Node Metastasis of Papillary Thyroid Carcinoma Detected by FDG PET/CT in a Thyroglobulin-Positive Patient With Negative Whole-Body 131I Scan

Axillary metastasis is not a common finding in papillary carcinoma. 18F-FDG can detect foci of metastasis in patients with negative 131I scan. We report a case of a 64-year-old man who had undergone thyroidectomy and 131I ablation due to classic type of papillary carcinoma 14 years ago. Follow-up examination revealed high serum thyroglobulin and negative whole body 131I scan. 18F-FDG PET/CT showed focally increased uptake in right axillary as well as supraclavicular and bilateral cervical lymph nodes. Histopathological examination of the surgically removed lymph nodes confirmed the metastasis of papillary thyroid carcinoma.

Use of 18FFDG-PET in patients with suspicion of recurrent differentiated thyroid cancer by elevated antithyroglobulin antibodies levels and negative 131I scan

Aim To evaluate the utility of 18FFDG-PET for patients diagnosed of differentiated thyroid carcinoma who present risk of disease and invaluable levels of thyroglobulin (Tg) by the presence of antibodies antithyroglobulin (AbTg). Material and methods Retrospective study of 7 women of 40 years old and histological diagnosis of differentiated thyroid cancer (7 papillary tumours) that were sent to our department for the accomplishment of 18FFDG-PET study because of suspicion of disease, due to 131I negative and high levels of AbTg, between the year 2002 and 2007. 11 PET scans were obtained after the intravenous injection of 370–434 MBq of 18FFDG in normoglycemia conditions and previous administration of muscle relaxant, hydration and diuretic. The results of 18FFDG-PET scans were confirmed by pathologic examination or clinical outcome and radiographic examination for more than 24 months. Results The prevalence of recurrence in our population was 57.14%. All patients presented levels of Tg lower than 3 ng/dl and AbTg superior to 200 UI/ml. Three patients had precedent thyroiditis. Out of 11 scans performed 3 of them were negative and 8 cases were found positive. It ruled out the existence of disease in three patients and localized the presence of recurrence in 4 patients. Conclusion 18F-FDG-PET is a useful diagnostic tool for the detection of recurrence as well as to rule out the existence of disease with a high accuracy, in patients with differentiated thyroid carcinoma with 131 I whole body scan negative but with pathological elevation of antithyroglobulin antibodies.

Role of 18F-fluorodeoxyglucose positron emission tomography/computed tomography in patients affected by differentiated thyroid carcinoma, high thyroglobulin level, and negative 131I scan: review of the literature

Differentiated thyroid carcinoma (DTC) is a slow-growing tumor that represents 1% of all malignant tumors and is the most frequent endocrine cancer. ¹⁸F-Fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT) imaging is an increasingly important imaging tool in oncology and is still under investigation in numerous studies looking into its efficacy and cost-effectiveness. Despite the fact that ¹⁸F-FDG-PET/CT has been shown to be a powerful and accurate diagnostic tool in patients affected by DTC with high serum thyroglobulin (Tg) levels and negative radioiodine (¹³¹I) total body scan, its definitive role is not completely clear, in particular regarding the role of thyroid stimulating hormone (TSH) and Tg value "cutoff" over which is better to perform the study. In this review, these issues are analyzed to clarify controversial aspects and identify established cornerstones. In particular, the literature analysis suggests that levothyroxine withdrawal is preferable in cases of relatively low Tg levels (<10 ng/ml) and good clinical compliance to hypothyroidism. Moreover, recombinant thyrotropin stimulating hormone (rTSH) could be a preferable alternative in patients clinically unable to tolerate therapy withdrawal. A Tg cutoff level over which to perform the study seems to be 10 ng/ml, a reasonable value maintaining high accuracy in terms of a good compromise between sensitivity and specificity.

Value of 18F-FDG-PET/PET-CT in differentiated thyroid carcinoma with radioiodine-negative whole-body scan: a meta-analysis

The aim of this study was to evaluate the diagnostic accuracy of 18F-fluorodeoxyglucose-PET (FDG-PET) and FDG-PET/computed tomography (CT) in the detection of recurrent or metastatic differentiated thyroid carcinoma (DTC) that was not identified by radioiodine whole-body scintigraphy (WBS). A total of 25 studies (comprising 789 patients) that were published from January 1990 to September 2008 were reviewed. These studies evaluated the role of FDG-PET and FDG-PET/CT in the detection of recurrent or metastatic DTC that radioiodine WBS failed to detect. Systematic methods were used to identify, select, and evaluate the methodological quality of the studies and to summarize the overall findings of sensitivity and specificity. In total, 17 studies with 571 patients who had recurrent or metastatic DTC and a radioiodine-negative whole-body scan were collected, and the overall patient-based sensitivity and specificity of FDG-PET were 0.835 [95% confidence interval (CI): 0.791-0.873] and 0.843 (95% CI: 0.791-0.886), respectively. Of these studies, six included lesion-based data, totaling 237 lesions, and the pooled lesion-based sensitivity and specificity were 0.916 (95% CI: 0.863-0.953) and 0.775 (95% CI: 0.660-0.865), respectively. The pooled sensitivity and specificity in the DTC patients who presented with elevated serum thyroglobulin and negative 131I scan were 0.885 (95% CI: 0.828-0.929) and 0.847 (95% CI: 0.715-0.934), respectively. In the six studies where the 165 patients were diagnosed by using FDG-PET/CT, pooled sensitivity and specificity were 0.935 (95% CI: 0.870-0.973) and 0.839 (95% CI: 0.723-0.920), respectively. FDG-PET is especially effective in detecting patients with elevated thyroglobulin levels and normal radioiodine WBS; FDG-PET/CT is a more sensitive method in the follow-up of thyroid cancer recurrence or metastases, particularly in those with negative WBS.

Follicular Thyroid Carcinoma Metastasis to the Esophagus Detected by 18FDG PET/CT

We report an unusual case of an esophageal metastasis demonstrated on integrated 18F-fluorodeoxyglucose (18FDG) positron emission tomography/computed tomography (PET/CT) scanning. A 55-year-old male with treated well-differentiated follicular thyroid carcinoma (FTC) had persistently raised thyroglobulin levels despite both negative whole-body CT scan and 131I scans. An initial 18FDG PET/CT scan showed moderate focal uptake in the esophagus, which was initially thought to be physiological. A subsequent comparative 18FDG PET/CT scan showed more intense uptake. A diagnostic endoscopy revealed a pedunculated esophageal polyp, which histological examination confirmed to be metastatic FTC. Such a case has not previously been reported.

Combined PET/CT in the follow-up of differentiated thyroid carcinoma: what is the impact of each modality?

18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a well-established method in the follow-up of patients with differentiated thyroid carcinoma (DTC), elevated thyroglobulin (Tg) and negative 131I scans. This retrospective clinical study was designed to evaluate the impact of computed tomography (CT) and that of FDG-PET in combined FDG-PET/CT examinations on the restaging of DTC patients. Forty-seven FDG-PET/CT scans of 33 patients with a history of DTC, elevated Tg levels and negative 131I uptake or additionally suspected 131I-negative lesions were studied. PET and CT images were analysed independently by an experienced nuclear medicine specialist and a radiologist. Afterwards a final consensus interpretation, the gold standard in our department, was provided for the fused PET/CT images and, if available, for supplementary investigations. Thirty-five investigations (74%) revealed pathological FDG-PET/CT findings. In summary, 25 local recurrences, 62 lymph node metastases and 122 organ metastases (41 lung, 60 bone, 21 other organs) were diagnosed. In 36 out of 47 examinations (77%), the original PET diagnoses were modified in the final consensus interpretation owing to the CT assessments. In 8 of the 35 pathological FDG-PET/CT examinations (23%), the final consensus interpretation of the PET/CT images led to an alteration in the treatment plan. PET/CT is a powerful fusion of two pre-existing imaging modalities, which not only improves the diagnostic value in restaging DTC patients with elevated Tg and negative 131I scan, but also provides accurate information regarding subsequent treatment options and may lead to a change in treatment management.

Which thyroid cancer patients need periodic stimulation tests?

Recurrences are frequent in thyroid cancer patients and long-term follow-up is therefore necessary. We evaluated the yield of rhTSH stimulation in three groups of patients, classified according to the UICC/TNM risk stratification and the results of first follow-up testing. The study population comprised 129 patients referred for rhTSH testing. All had undergone first follow-up testing after thyroid hormone withdrawal (off-T4) within 1 year of 131I ablation. Negative first follow-up testing was defined as Tg <2 ng/ml and no neck uptake on 131I diagnostic whole-body scan. Seventy-five patients had stage I thyroid cancer and negative first follow-up testing (group A), 19 had stage I disease and positive first follow-up testing (group B), and 35 had stage II-IV disease (group C). RhTSH stimulation was performed an average of 6 years after first follow-up testing. 131I diagnostic scanning after rhTSH was negative in all 75 group A patients. Only one group A patient had detectable Tg after rhTSH injection (1.5 ng/ml), but Tg had also been detected at baseline in this patient (1.45 ng/ml). Given the absence of a response to stimulation, suggesting an interference, Tg was reassessed with a different technique and proved to be undetectable (<0.1 ng/ml). Stimulation with rhTSH in group B showed residual Tg in seven patients and residual 131I uptake in the thyroid bed in two patients, but none of these patients had signs of disease progression. Five group C patients (14%) had a positive rhTSH test result, and this was suggestive of disease progression in at least two cases. The first follow-up testing is essential for prognostic classification after 131I ablation of thyroid cancer. In stage I patients, undetectable Tg and negative 131I scan 1 year after ablation define a large population of subjects who have a very low risk of recurrence and who do not require further stimulation tests. In contrast, periodic rhTSH stimulation tests appear useful in higher-risk patients.

Combined Positron Emission Tomography/Computed Tomography Imaging of Recurrent Thyroid Cancer

The study goal was to evaluate the use of combined positron emission tomography/computed tomography (PET/CT) imaging for localization of recurrent disease in thyroid cancer patients. Eight patients with suspected recurrence of thyroid cancer on the basis of elevated serum thyroglobulin or calcitonin levels underwent combined PET/CT imaging on a prototype device. All 8 patients had previously undergone total thyroidectomy and (131)I ablation for thyroid carcinoma. Patients with papillary carcinoma had negative (131)I scans. Eight patients underwent combined PET/CT scanning. Four (50%) of 8 patients underwent PET/CT indicating recurrence in the head and neck. A total of 11 lesions in these 4 patients were suspicious for recurrence on combined PET/CT imaging. Three patients with 8 lesions suspicious for recurrence on PET/CT underwent surgical removal of disease. All 3 patients had pathologic confirmation of recurrence, with 6 (75.0%) of 8 lesions being positive. Combined PET/CT imaging is a valuable tool for the diagnosis and anatomic localization of recurrent thyroid cancer.

Whole-body FDG-PET imaging in the management of patients with cancer

Fluorodeoxyglucose-positron emission tomography (FDG-PET) imaging is increasingly used for the management of patients with cancer. The technique is now well accepted by most physicians as an effective complement to the existing imaging modalities. For many malignancies, PET achieves high sensitivity and specificity. The critical role of this powerful technique is realized increasingly in the day-to-day practice of oncology. This is particularly true for the management of patients with non-small-cell lung cancer (NSCLC). The contribution of PET for the selection of patients eligible for curative treatments in this setting is well established. Convincing data also exist to support the use of PET for evaluating patients with recurrent colorectal carcinoma, for staging and restaging lymphomas, and for diagnosing recurrent thyroid carcinoma in the presence of elevated thyroglobulin and negative 131I scans. Other indications include staging of various recurrent malignancies, such as breast cancer, melanoma, and head and neck and gynecologic carcinomas. Existing data are limited for the determination of the impact of PET in certain malignancies, and further studies, which should include outcome information, will allow clarification of the role of this modality for such indications. Despite the small number of studies specifically designed to assess changes in management plans for some malignancies after performing PET the overall favorable results are encouraging enough at this time to include this modality as an essential element of the practice of modern oncology. Finally, the evolving role of PET imaging as a predictor of response after local or systemic treatment may add a major dimension to the application of this novel technique.

ISOTOPE IMAGING FOR METASTATIC THYROID CANCER

Many isotopes are available for imaging patients with suspected thyroid cancer recurrence and metastases. TSH-stimulated low-dose 131I whole-body scanning with serum thyroglobulin either by standard LT4 withdrawal or rhTSH stimulation is the preferred test for monitoring patients without palpable disease or elevated serum thyroglobulin on LT4 therapy (Fig. 5). This approach has the advantage of finding disease that may be amenable to 131I therapy, although low-dose 131I scans are less sensitive than are scans with other imaging agents. 123I has better imaging characteristics than 131I and has been shown to be equivalent or superior to low-dose 131I in recent studies. As the availability of 123I increases and the cost decreases, this agent may replace 131I in imaging for recurrent or metastatic thyroid cancer. Patients who have an elevated serum thyroglobulin on LT4 therapy or after TSH stimulation but have a negative low-dose 131I scan require other imaging procedures to find the suspected disease. The authors currently perform a sensitive neck ultrasound to look for surgically remediable disease and consider a noncontrast CT scan of the chest to look for small pulmonary metastases that poorly concentrate low doses of 131I (Fig. 5). Fluoro-18-deoxyglucose PET, 99mTc MIBI, 201Tl, and 99mTc tetrofosmin are primarily useful in the setting of a negative whole-body 131I scan and elevated serum thyroglobulin. 18FDG-PET seems to have the highest sensitivity in this setting and would be the preferred imaging agent, but availability and cost are major issues (Fig. 5). Although some researchers have advocated these radiopharmaceuticals as first-line agents replacing 131I, there is little support for this position. This approach to imaging is not cost-effective because positive scans in these patients would most likely require 131I scintigraphy to determine whether the lesions are amenable to radioiodine therapy. 99mTc pertechnetate, 99mTc furifosmin, and somatostatin receptor scintigraphy have a limited role in imaging for recurrent or metastatic differentiated thyroid carcinoma. In choosing among 99mTc MIBI, 201Tl, and 99mTc tetrofosmin, the technetium label of sestamibi and tetrofosmin results in better image quality and faster imaging than 201Tl. Although 99mTc sestamibi and 99mTc tetrofosmin have not been compared in a large series, the higher tumor-to-background ratio and consistently high sensitivities of 99mTc tetrofosmin suggest that it could potentially have additional value over 99mTc sestamibi, but there is still limited experience with 99mTc tetrofosmin.

Positron emission tomography of the thyroid, with an emphasis on thyroid cancer.

The role of Positron Emission Tomography (PET) using 18F-fluorodeoxyglucose (FDG) in the management of thyroid cancer is discussed. It is important to ensure that patients are relaxed because uptake of FDG in tense or active muscles in the neck and larynx can be misinterpreted as metastases. The major role for PET is in patients where the stage of disease is uncertain, usually the result of discordant negative 131I scan and a positive serum thyroglobulin (Tg) values. PET identifies the source of Tg production in 50-80% of patients. PET scan can be negative in well differentiated cancers which retain the ability to trap iodine. This can result in a 'flip/flop', with negative PET, positive radio-iodine scan, or positive PET, negative radioiodine scan. PET is also valuable in identifying the source of calcitonin production in patients with medullary thyroid cancer. When focal uptake is seen in the thyroid of patients who are scanned for non thyroidal reasons, the likelihood of primary thyroid cancer is high. In contrast diffuse uptake of FDG in the thyroid is usually the result of auto-immune thyroid disorders.

Value of preoperative diagnostic modalities in patients with recurrent thyroid carcinoma

Abstract Background The prognosis of differentiated thyroid carcinoma is usually excellent, but the majority of patients who develop a recurrence have a higher risk of death from the disease. Beside clinical examination, several diagnostic tools, such as ultrasonography, 131I scanning, [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) and thyroglobulin (TG) measurement under raised thyroid-stimulating hormone in serum can detect tumour recurrences. This prospective study compared the value of different diagnostic modalities in the detection of recurrent differentiated thyroid cancer. Methods From April 1992 to October 1999, 181 patients with thyroid carcinoma, of whom 150 had a well differentiated tumour, subjected to surgical treatment were identified prospectively. Some 107 patients (71 per cent) presented with primary tumour and 43 patients (29 per cent) with recurrent disease. The patients with tumour recurrence were evaluated regarding the mode of detection of recurrent disease, including clinical examination, ultrasonography, fine-needle biopsy (FNB), TG measurement and FDG-PET, the surgical treatment and outcome. Results Some 63 per cent of patients presented with regional lymph node metastases and 37 per cent with local recurrence. None of the patients with local recurrence was operated on for primary tumour in this department. In 87 per cent the recurrence was detected by clinical examination. Ultrasonography and 131I scan revealed suspicious findings in 97 and 69 per cent respectively. FNB disclosed abnormal cytological findings in 95 per cent. There were pathological TG levels in 86 per cent of patients. Among patients with a raised level of TG and negative scan results, 13 underwent FDG-PET, with pathological findings in 82 per cent. Conclusion In patients with well differentiated thyroid carcinoma, ultrasonography and FNB are the most sensitive methods for the detection of local recurrence or regional lymph node metastases. FDG-PET is a useful diagnostic tool in patients with a negative 131I scan and a raised level of TG.

Utility of fluorine-18-fluorodeoxyglucose positron emission tomography in differentiated thyroid carcinoma with negative radioiodine scans and elevated serum thyroglobulin levels

Background: This study aimed to determine the role of fluorine-18-fluorodeoxyglucose positron emission tomography (FDG-PET) in the follow-up of patients who underwent total thyroidectomy and iodine-131 ( 131I) ablation therapy for differentiated thyroid cancer and presented increased thyroglobulin levels with negative 131I and thallium-201 ( 201Tl) scans. Methods: Two patients with follicular carcinoma and eight with papillary tumors underwent total thyroidectomy and 131I therapy until the 131I scan was negative. 131I and 201Tl scans were performed with negative results in all cases, while serum thyroglobulin measurements were all positive with negative thyroglobulin autoantibodies. One week after the 131I scans, all the patients underwent FDG-PET whole-body scans. Results: The FDG-PET scan detected in 4 patients, a single focal increase of FDG uptake in one lymph node metastasis (subsequently confirmed histologically); in 1 patient, multiple pathological focal uptakes in brain, neck, and chest; and in 1 patient, two mild focal uptakes in the mediastinum, close to the tracheal branch. In 2 other patients, pathological FDG uptakes in cervical spine and mediastinum were not confirmed by other imaging techniques, and in the 2 remaining patients the scan results were inconclusive. The sensitivity of FDG-PET whole-body scan for detecting metastatic thyroid cancer was 60%. Conclusions: This study indicates that the FDG-PET whole-body scan is a useful tool in the follow-up of patients with differentiated thyroid cancer, negative 131I and 201Tl scans and elevated serum thyroglobulin levels. The FDG-PET scan detects metastatic disease in 60% of patients with differentiated thyroid cancer, enabling surgical therapy to be performed on accessible lesions.

The role of technetium-99m methoxyisobutylisonitrile scintigraphy in the planning of therapy and follow-up of patients with differentiated thyroid carcinoma after surgery.

The aim of this study was to investigate the possible role of technetium-99m methoxyisobutylisonitrile (MIBI) scan in planning post-surgical therapy and follow-up in patients with differentiated thyroid carcinoma (DTC). Four groups of DTC patients were considered: Group 1 comprised 122 patients with high serum thyroglobulin (s-Tg) levels and negative high-dose iodine-131 scan during follow-up who had previously undergone total thyroidectomy and 131I treatment. Group 2 consisted of 27 patients who had previously undergone total thyroidectomy and 131I treatment but were now considered disease-free; this group was considered as controls. Group 3 comprised 49 patients studied after total thyroidectomy but prior to 131I scan. Finally, group 4 consisted of 21 patients who had previously undergone partial thyroidectomy alone. MIBI scan, neck ultrasonography (US), and s-Tg measurements during suppressive hormonal therapy (SHT) were obtained in all patients. Neck and chest computed tomography (CT) or magnetic resonance imaging (MRI) was also performed in group 1 patients. In group 1, MIBI scan and US were very sensitive in detecting cervical lymph node metastases (93.54% and 89.24%, respectively). Furthermore, MIBI scan and US played a complementary role in several patients, yielding a global sensitivity of 97.84%. In contrast, CT/MRI sensitivity for cervical lymph node metastases was very low (43.01%). MIBI scan also showed a higher sensitivity than CT/MRI in detecting mediastinal lymph node metastases (100% vs 57.89%). Regarding distant metastases, MIBI scan provided results similar to those of conventional imaging (CT, MRI, 99mTc-methylene diphosphonate bone scan). In group 2, no false-positive cases were observed with MIBI scan (100% specificity). In group 3, MIBI scan correctly identified all the 131I-positive metastatic foci, except in two patients with micronodular pulmonary metastases that were visualised with 131I scan. In contrast, both MIBI scan and US showed low sensitivity (46.15% and 61.53%, respectively) compared with 131I scan in detecting thyroid remnants. s-Tg was increased in all patients with distant metastases but only in 56% of those with lymph node metastases. Furthermore, s-Tg was increased in 21.42% of patients with thyroid remnants alone (false-positive results). In group 4, MIBI scan was the only examination capable of detecting at an early stage a mediastinal lymph node metastasis in one patient. We conclude that the integrated MIBI scan/neck US protocol: (a) can be proposed as a first-line diagnostic procedure in the follow-up of DTC patients with high s-Tg levels and negative high-dose 131I scan, and (b) may be helpful in the follow-up of DTC patients who undergo partial thyroidectomy alone. Moreover, the combined MIBI scan/neck US/s-Tg protocol appears to be highly sensitive in identifying patients with metastatic disease after total thyroidectomy and prior to 1311 scan; consequently, it may play a prognostic role in distinguishing high-risk from low-risk DTC patients. However, due to the low sensitivity of MIBI scan and neck US in detecting thyroid remnants, this diagnostic approach cannot be used as a predictor of 131I scan results. Lastly, because of the high sensitivity of MIBI scan and neck US in revealing both functioning and non-functioning metastases, this integrated protocol might be helpful in the follow-up of high-risk DTC patients, particularly for the early detection of lymph node metastases in patients with undetectable s-Tg during SHT.

Nuclear imaging in the management of thyroid carcinoma.

The avidity of differentiated thyroid carcinoma for iodine is the basis for the use of radioiodine (131I) both for the detection and the treatment of recurrent thyroid cancer in patients following initial surgical treatment (thyroidectomy). Because recurrence of this type of cancer may be delayed for many years, long-term follow-up is needed. Nowadays such surveillance involves clinical assessment, monitoring of serum thyroglubulin, and, when indicated, whole-body imaging with 131I. Sensitivity of 131I imaging depends on proper preparation of the patient and careful attention to imaging technique. Interpretation of images requires knowledge of physiologic sites of radioiodine concentration and causes of artifacts. Because of the potential suppressive effect of the radiation from a diagnostic administration of 131I on the uptake of a subsequent therapeutic administration (so-called stunning of thyroid tissue) many centers limit the amount given for scanning to 2-3 mCi (74-111 MBq). Several tumor-seeking radioisotopic agents other than radioiodine have shown promise for improving the detection of metastases, and some of these agents offer a useful adjunct to 131I in the management of selected patients, particularly in those with suspected metastatic disease and negative 131I scans.

Pulmonary metastasis of differentiated thyroid carcinoma: treatment results in 101 patients.

Well differentiated thyroid carcinoma was diagnosed in 1,127 patients at The University of Texas M.D. Anderson Hospital and Tumor Institute at Houston from 1951 to 1981. Of those 1,127 patients, 101 had documented pulmonary metastasis. A retrospective analysis was conducted, and these patients were followed up until 1983. The primary tumors in these patients were histologically classified as papillary (67%), follicular (22%), or Hurthle cell (11%). The age at diagnosis ranged from 5-87 yr. Lung metastasis was diagnosed by both chest x-ray and positive uptake of 131I in 49 patients. Forty-two patients had positive chest x-ray results and negative 131I scans, and 10 patients had positive 131I scans and negative chest x-ray results. The patients were treated with radioactive iodine (76%), chemotherapy (9%), external radiotherapy (2%), or supportive care only (14%). Sixty-seven patients subsequently died of thyroid carcinoma. Our studies showed the following. 1) Patients who were younger than 40 yr of age at diagnosis had better prognosis (71% survival) compared with those over 40 yr of age (16% survival; P less than 0.01). 2) Uptake of radioactive iodine by lung metastasis is a favorable prognostic factor, especially in patients with negative radiological findings. Patients treated with radioactive iodine have a longer survival than those not treated with radioactive iodine (P less than 0.002). 3) The incidence of pulmonary metastasis is significantly less in patients who are treated by total thyroidectomy than in those treated with less than total thyroidectomy (P less than 0.03). 4) The incidence of pulmonary metastasis is lowest in patients with papillary carcinoma (9%), compared with that in patients with follicular (13%) or Hurthle cell (25%) carcinoma.