Inhibition of metabolic activity in papillary thyroid carcinoma by a somatostatin analogue

Refractory thyroid carcinoma: which systemic treatment to use?

The incidence of thyroid cancer has increased markedly in recent decades, but has been stable in terms of mortality rates. For the most part, these cancers are treated with surgery, which may or may not be followed by radioactive iodine depending on the tumor subtype. Still, many of these cancers will recur and may be treated with radioactive iodine or another surgery. It is unclear what treatment is best for cases of locally advanced or metastatic thyroid cancer that are refractory to radioactive iodine. Chemotherapy has a very low response rate. However, in the past few years, several systemic therapies, primarily targeted, have emerged to improve the overall survival of these patients. Alternative treatments are also of interest, namely peptide receptor radionuclide therapy or immunotherapy.

Utility of (99m)Tc-Hynic-TOC in 131I Whole-Body Scan Negative Thyroid Cancer Patients with Elevated Serum Thyroglobulin Levels

Several studies have reported on the expression of somatostatin receptors (SSTRs) in patients with differentiated thyroid cancer (DTC). The aim of this study was to evaluate the imaging abilities of a recently developed Technetium-99m labeled somatostatin analog, (99m)Tc-Hynic-TOC, in terms of precise localization of the disease. The study population consisted of 28 patients (16 men, 12 women; age range: 39-72 years) with histologically confirmed DTC, who presented with recurrent or persistent disease as indicated by elevated serum thyroglobulin (Tg) levels after initial treatment (serum Tg > 10 ng/ml off T4 suppression for 4-6 weeks). All patients were negative on the Iodine-131 posttherapy whole-body scans. Fluorine-18 fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) was performed in all patients. SSTR scintigraphy was true positive in 23 cases (82.1%), true negative in two cases (7.1%) and false negative in three cases (10.7%) which resulted in a sensitivity of 88.46%, specificity of 100% and an accuracy of 89.2%. Sensitivity of (99m)Tc-Hynic-TOC scan was higher (93.7%) for patients with advanced stages, that is stages III and IV. (18)F-FDG showed a sensitivity of 93.7%, a specificity of 50% and an accuracy of 89.3%. (18)F-FDG PET was found to be more sensitive, with lower specificity due to false positive results in 2 patients. Analysis on a lesion basis demonstrated substantial agreement between the two imaging techniques with a Cohen's kappa of 0.66. Scintigraphy with (99m)Tc-Hynic-TOC might be a promising tool for treatment planning; it is easy to perform and showed sufficient accuracy for localization diagnostics in thyroid cancer patients with recurrent or metastatic disease.

[Treatment of patients with radioiodine refractory, differentiated thyroid carcinoma. A Consensus Statement]

There is no clear standard therapy for patients with radioactive iodine (131I)-refractory locally advanced or metastatic differentiated thyroid cancer. The therapeutic options for this indication have expanded with the recently approved multiple kinase inhibitor sorafenib. Recommendations for the definition and the management of iodine refractory patients were worked up by an interdisciplinary expert panel, consisting of endocrine surgeons, medical oncologists and nuclear medicine specialists.

Somatostatin receptor expression in thyroid disease

Somatostatin analogues are commercially available and used for the management of acromegaly and neuroendocrine tumours, but the expression of the receptors as a target in thyroid disease has not been explored. To assess somatostatin (SST) and somatostatin receptor (SSTR1-5) expression in both normal and thyroid disorders, as a potential target for somatostatin analogue therapy, 67 thyroid tissue specimens were reviewed: 12 differentiated thyroid carcinomas, 14 follicular adenomas, 17 multinodular goitres, 14 Graves disease, 10 Hashimotos thyroiditis specimens and five normal thyroids. Tissue was immunostained for SST and SSTR1-5. Positivity and the degree of positivity were recorded by double-blinded observers. Somatostatin receptor expression was highly expressed in normal tissue for SSTR1, 3, 4 and 5 (5 of 5, 4 of 5, 4 of 5 and 5 of 5 respectively) whilst SST and SSTR 2a and b were not expressed at all. The commonest receptor expressed for all pathological subtypes grouped together was SSTR2b (63 specimens). The commonest receptors expressed in differentiated thyroid cancer were SSTR5 (11 of 12 specimens) and SSTR2b (10 of 12 specimens). The commonest receptor expressed in benign disease was SSTR2b (53 of 55 specimens). SSTR5 was significantly under-expressed in Graves disease (P < 0.05). This study illustrates that SSTR 1, 3, 4 and 5 are highly expressed in normal, benign and malignant thyroid tissue. SSTR 2a and 2b appear absent in normal tissue and present in benign and malignant thyroid tissue (P < 0.02). This suggests that focussed SSTR2 treatment may be a potential therapeutic target.

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.

New therapeutic approaches for metastatic thyroid carcinoma

Treatment of metastatic differentiated thyroid cancer (DTC) includes the use of radioiodine and suppressive thyroid hormone treatment. A third of patients with distant metastases (who have radioiodine uptake, are younger than 40 years, have small metastases, and have well differentiated thyroid tumour) can be cured with radioiodine treatment. For other patients, there are no effective treatment modalities. However, the recent availability of molecularly targeted treatments has led to changes in the treatment strategy for DTC in patients with distant metastases, especially in those who are resistant to radioiodine treatment.

Is there a role for sandostatin treatment in patients with progressive thyroid cancer and iodine-negative but somatostatin-receptor-positive metastases?

INTRODUCTION

The aim of our study was to determine whether treatment with a long-acting somatostatin-receptor analogue is effective in patients with (131)I-negative but somatostatin-receptor-positive metastases from dedifferentiated and anaplastic thyroid cancer.

MATERIALS AND METHODS

Twelve patients were screened for the study. All of them showed progressive disease confirmed by radiologic evaluation, increasing serum thyroglobulin (Tg), and negative diagnostic or posttherapeutic (131)I whole-body scans (WBS). Eight of 12 patients (4 males and 4 females; age range, 57-89 years; 1 papillary thyroid cancer; 4 poorly differentiated follicular thyroid cancer; 1 follicular and anaplastic thyroid cancer; 2 anaplastic thyroid cancer) showed positive somatosatin-receptor expression in Tc-99m depreotide WBS/SPECT (Tc-99m Dep.WBS). Initially, in all patients fluorine-18 2-fluoro-2- D-glucose-positron emission tomography-computed tomography ((18)F-FDG-PET-CT), Tc-99m Dep.WBS, and Tg measurements were performed. In the case of positive receptor scintigraphy, patients were treated with 20mg Sandostatin LAR (Novartis Pharmaceuticals, Basel, Switzerland) once per month intramuscularly over a period of 6 months followed by repeated (18)F-FDG-PET-CT, Tc-99m Dep.WBS, and Tg measurement to determine metabolic activity and tumor size. In case of tumor progression, the dose was increased to 30mg of Sandostatin LAR once per month.

RESULTS

Only 3 patients were able to undergo long-term treatment. Two patients were treated with octreotide long-acting release (LAR) for 1 year and 1 patient for 1(1/2) years. All patients showed progressive disease during the treatment: an increase of serum Tg on one hand and an increase in the number of lesions and extent in tumor size visible on FDG-PET-CT and Tc-99m Dep.WBS on the other. During the treatment there was no change in receptor expression, nevertheless, clear tumor progression under therapy with a somatostatin analogue was visible in FDG-PET-CT and in Tc-99m Dep.WBS.

CONCLUSION

Our data demonstrate that all of our patients treated with a somatostatin analogue showed clinical progression and that our attempt to achieve a stabilization of the disease failed.

Staging and treatment of differentiated thyroid carcinoma with radiolabeled somatostatin analogs

In patients with progressive metastatic (or recurrent) differentiated thyroid carcinoma that either do not take up radioiodine or are unresponsive to continued radioiodine therapy, staging is difficult and treatment options are few. However, in most of these patients uptake of radiolabeled somatostatin analogs is evident on somatostatin-receptor scintigraphy (SRS). Using SRS, patients with sufficient uptake of radiolabeled somatostatin analogs can be selected for high-dose peptide receptor radionuclide therapy (PRRT) as an alternative targeted-treatment option. PRRT with the beta-particle-emitting radionuclides (90)yttrium ((90)Y) and (177)lutetium ((177)Lu) gives the best results in terms of objective tumor response. Promising, novel, radiolabeled somatostatin analogs that have a broader receptor affinity profile and, thus, a potentially wider therapeutic range are being tested clinically.

Six month follow-up after 111In-DTPA-octreotide therapy in patients with progressive radioiodine non-responsive thyroid cancer: a pilot study

BACKGROUND AND AIM

111In-DTPA-octreotide is internalized by thyroid and neuroendocrine cancer cells via somatostatin receptor subtypes and can cause DNA damage by the emission of conversion and Auger electrons. The aim of the study was to determine the effect of 111In-DTPA-octreotide therapy in patients with progressive radioiodine non-responsive thyroid cancer in relation to 111In-DTPA-octreotide uptake by tumour localizations assessed on pre-treatment diagnostic octreotide scans.

METHODS

Eleven consecutive patients, selected on positive pretreatment diagnostic scans, were treated with fixed doses of approx. 7400 MBq of 111In-DTPA-octreotide with an interval of 2-3 weeks between the doses. In one patient, the dose was adjusted because of sickle-cell disease. To assess the effects during treatment with 111In-DTPA-octreotide thyroglobulin levels were gathered from 2 years before treatment, during treatment and up to 1 year after treatment. A computed tomography scan was performed 3 months after the last treatment.

RESULTS

Two patients died during and shortly after the treatment course. Death was due to a sepsis and an insulin overdose, respectively. In 44% of the patients, stable disease was achieved up to 6 months after the first treatment according to both criteria. All four had relative low pretreatment thyroglobulin values (mean value 275 microg.l), representing limited metastasized disease. In two patients biochemical stable disease was observed, whereas computed tomography showed tumour progression.

CONCLUSION

Treatment with high doses of 111In-DTPA-octreotide in differentiated thyroid cancer results in a stable disease in a subgroup of patients. Our results suggest that a low pre-treatment thyroglobulin value, representing a small tumour load, may be a selection criterion for treatment.

Somatostatin receptors: from basic science to clinical approach--thyroid

Somatostatin and its receptors are expressed in the thyroid gland, but somatostatin analogs which are currently available have provided contradictory results in the diagnosis and treatment of thyroid neoplasia. Somatostatin and its analogs fail to influence follicular thyroid function, whereas their administration in patients with medullary thyroid carcinoma induces a reduction of serum calcitonin concentrations and clinical symptoms, but fails to influence tumour size and patient survival rate. Radiolabelled somatostatin analogs can localise tumours expressing somatostatin receptors, but somatostatin receptor-targeted radiotherapy of thyroid malignancies has provided conflicting and inconclusive results. Our recent results indicate that somatostatin receptor 2 activation by somatostatin receptor 2 agonists inhibits cell proliferation in the human medullary thyroid carcinoma cell line, TT. This effect can be hampered by concurrent somatostatin receptor 5 selective agonist treatment, which fails to influence TT cell proliferation, suggesting an antagonism between somatostatin receptors 5 and 2 agonists in medullary thyroid carcinoma cells. Moreover, somatostatin receptors 2 or 5 agonists fail to inhibit calcitonin secretion and calcitonin gene expression. On the other hand, somatostatin receptor 1 agonists inhibit proliferation, calcitonin secretion and calcitonin gene expression in parafollicular C cells, suggesting that analogs with enhanced somatostatin receptor 1 affinity and selectivity besides having great potentiality as pharmacological tools to control neoplastic growth, may also be used to reduce symptoms in patients with medullary thyroid carcinoma.

99mTc-EDDA/HYNIC-TOC and (18)F-FDG in thyroid cancer patients with negative (131)I whole-body scans

Several studies have reported on the expression of somatostatin receptors in patients with differentiated thyroid cancer (DTC). The aim of this study was to evaluate the imaging abilities of a recently developed technetium-99m labelled somatostatin analogue, (99m)Tc-EDDA/HYNIC-TOC ((99m)Tc-TOC), in terms of precise localisation of disease. The study population comprised 54 patients (24 men, 30 women; age range 22-90 years) with histologically confirmed DTC who presented with recurrent or persistent disease as indicated by elevated Tg levels after initial treatment. All patients were negative on the iodine-131 post-therapy whole-body scans. Fluorine-18 fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) was performed in a subgroup of 36 patients. The study population consisted of two groups: Group A ( n=22) comprised patients with disease recurrence as shown by elevated Tg levels but without detectable pathology. In group B ( n=32), pre-existing lesions were known. Among the 54 cases, SSTR scintigraphy was true positive in 33 (61.1%), true negative in 4 (7.4%) and false negative in 17 (31.5%) cases, which resulted in a sensitivity of 66%. A total of 138 tumour foci were localised in 33 patients. The fraction of true positive (99m)Tc-TOC findings was positively correlated ( P<0.01) with elevated Tg levels (higher than 30 ng/ml). Despite two false positive findings, analysis on a lesion basis demonstrated better diagnostic efficacy with (18)F-FDG PET ( P<0.001); however, it also revealed substantial agreement between the imaging techniques [Cohen's kappa of 0.62 (0.47-0.78)]. In conclusion, scintigraphy with (99m)Tc-TOC might be a promising tool for treatment planning; it is easy to perform and showed sufficient accuracy for localisation diagnostics in thyroid cancer patients with recurrent or metastatic disease.

Indium-111-Octreotide scintigraphy in differentiated thyroid carcinoma metastases that do not respond to treatment with high-dose I-131

AIM

Differentiated thyroid cancer is characterized by a very good prognosis in the majority of the patients. The therapy of choice is surgery followed by ablation with Iodine-131 (I-131). However, some patients have metastases that have lost the capability of concentrating I-131, even when it is given in therapeutic doses. In the present study, we describe the value of Indium-111 Octreotide (Octreoscan) in differentiated thyroid cancer patients with increased Tg levels who failed to demonstrate a response to treatment with high-dose I-131.

METHOD

Fifteen consecutive patients with progressive differentiated thyroid cancer (ten female, five male) (mean age: 59 years, range 13-81 years; eight papillary, six follicular, and one Hürthle cell carcinoma) were studied. Progression was based on increasing Tg levels and was confirmed by radiological evaluation. Whole body scintigraphy (WBS) was performed after the administration of 200 MBq of Indium-111-Octreotide. The images were assessed by two experienced observers and compared with post-treatment I-131 WBS.

RESULTS

In seven out of 15 patients distant metastases were already present at initial stage, whereas in ten patients the primary tumor stage was T3 or T4 indicating that the majority of the patients had advanced disease. In two out of five patients with a positive I-131 WBS, Indium-111-Octreotide was false negative. In nine out of ten patients with a negative I-131 WBS, Indium-111-Octreotide demonstrated multiple metastases. In those patients with a positive SSR-scintigraphy, metastases were found in the lungs ( n=14), bone ( n=7), mediastinum ( n=3), liver ( n=2), brains ( n=1), and cutis ( n=1). Overall, three out of 15 patients had a negative Indium-111-Octreotide result revealing a sensitivity of 80%.

CONCLUSION

Our findings demonstrate the diagnostic value of Indium-111-Octreotide in differentiated thyroid cancer that fails to respond to I-131 treatment. It opens the possibility for additional treatment with high doses of Indium-111-Octreotide or its analogs in a majority of the patients.

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

PURPOSE

The utility of In-111 DTPA octreotide scintigraphy (SRS) for disease detection in patients with metastatic thyroid carcinoma (TCA) remains controversial. The authors compared the sensitivity of In-111-based SRS, F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET), and extensive conventional radiographic imaging (CRI) in this type of cancer.

METHODS

SRS, FDG PET, and CRI were performed concurrently in 21 patients (age, 56.4 +/- 12.9 years) who had aggressive TCA. Concordance rates % of lesion positivity among pairs of different techniques (A and B) were calculated as the ratio of the number of lesions positive with both techniques divided by the sum of the total number of lesions positive with technique A + total number of lesions positive with technique B, which was then multiplied by 200.

RESULTS

The combined use of CRI, FDG PET, and SRS resulted in the detection of 105 lesions, presumed to be due to metastatic deposits. Sensitivities for SRS and FDG-PET imaging were 49.5% and 67.6%, respectively. The lesion detection concordance rates were as follows: CRI versus FDG PET, 80.8%; CRI versus SRS, 74.2%; and FDG-PET versus SRS, 58.6%. Importantly, SRS detected five unexpected lesions, which were negative by both CRI and FDG-PET imaging. In two representative patients, a positive correlation (Spearman's rank = 0.71; = 0.0576) existed between the percentage of lesional In-111 DTPA octreotide uptake and the standard uptake value in eight concordant lesions.

CONCLUSION

Although SRS has only moderate sensitivity for disease detection in metastatic TCA, sometimes it can reveal lesions that otherwise would be undetectable by either CRI or FDG-PET imaging.

Positron emission tomography in thyroid cancer management

Selected patients with thyroid cancer can benefit from the use of PET imaging with FDG or with I-124. The PET scan impacts on management by providing (1) more accurate information about staging of patients in terms of extent of tumor for better treatment planning, especially in patients who do not concentration radioactive I-131; (2) the relationship of tumor involvement to vital structures, especially in the neck and central nervous system; and (3) prognostic information (an SUV > 10 and extensive PET + disease connotes a poor prognosis in advanced patients). In the occasional patient, surgically respectable disease has been identified on PET with the result that the patient has been rendered no evident disease with treatment. PET has also been used in the follow-up of patients who have been treated for thyroid cancer, to assess response. PET may also be useful for lesion specific dosimetry, with I-124. The combination of PET and CT in the same gantry facilitates localization of thyroid cancer PET scan abnormalities in relationship to critical organs and structures.

Somatostatins and their role in thyroid cancer

Somatostatins are neuropeptides that exert a downregulatory effect on various physiological processes. Somatostatin analogues are used in the imaging and management of various tumour types. Their role in thyroid cancer has not as yet been fully elucidated. A systematic review of the literature using the keywords thyroid, cancer and somatostatin revealed 263 references. This paper summarizes the current knowledge of the role of somatostatins in thyroid cancer and assesses their future potential.

[Therapeutic advances of nuclear medicine in oncology]

With the development of new radiopharmaceuticals there is a tendency to apply nuclear medicine therapy for malignancies of higher incidence (lymphoma, prostate) than the ones which have been treated for many years (thyroid cancer, neuroendocrine tumours). One of the most important areas of current development in radionuclide cancer therapy is the monotherapeutic use of new or already available radiopharmaceuticals in preclinical or phase I studies and to a lesser degree in phase II trials. In this context, the radioimmunotherapy is showing important advances in the treatment of medullary thyroid carcinoma, malignant lymphomas en brain tumours with potential extension to neuroblastoma therapy. The development of DOTA as a chelating agent has lead to the use of Y-90-DOTATOC in the treatment of neuroendocrine tumours, particularly carcinoid tumours, and non-I131I-avid thyroid carcinomas. In an effort to improve tumour targeting together with simultaneous reduction of physiological organ uptake, 131I-MIBG is being used in combination with interferon a and pre-targeting with unlabelled MIBG in the treatment of carcinoid tumours. New routes of administration of radiopharmaceuticals (intratumoral, intra-arterial) have enhanced the treatment of malignancies of liver, pancreas and brain as well as the potential use of radioimmunotherapy by intravesical administration for bladder carcinoma. Another significant tendency in radionuclide therapy is its evolution from monotherapy towards a combined application with other anticancer modalities. Some recent examples of combined therapy with demonstrated anti-tumour effect are found in neuroblastoma (131I-MIBG and chemotherapy), bone metastases of prostatic carcinoma (addition of 89Sr to chemotherapy schedules), brain malignancies (adjuvant use of radioimmnunotherapy in relation to surgery and external radiotherapy) and lymphoma (radioimmunotherapy combined with chemotherapy or immunotherapy). Reinforcing this trend in phase II and III studies as well as the planning of multicenter trials following the guidelines and criteria of clinical oncology will determine the future advances in this field.

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.

Differentiated thyroid carcinoma in the elderly

The overall prognosis of patients with differentiated thyroid cancer is excellent, but the prognosis is rapidly worsening, when the disease is diagnosed in elderly patients. Old patients more often present with poor prognostic features, such as large tumors, follicular or Hürthle cell subtypes, extrathyroidal growth and distant metastases. Therefore, an optimal therapeutic approach is recommended. Current therapy includes a total thyroidectomy, if necessary combined with a lymph node dissection and followed by high dose radioiodine ablation. Radioiodine therapy in elderly patients meets specific problems, concerning thyroid hormone withdrawal, side effects of 131I and nursing problems. Additional treatment of residual, recurrent or metastatic disease must be tailored, according to the stage of the disease, and should not be denied on the basis of chronological age. Lifelong treatment with suppressive thyroid hormone therapy does not lead to important long-term side effects at old age.