Cerebellar metastasis of papillary thyroid carcinoma detected with somatostatin receptor scintigraphy.

INTRODUCTION: Distant metastases of papillary thyroid carcinoma (PTC) may lack the ability to concentrate radioiodine. In such cases, positive somatostatin receptor scintigraphy might be useful in demonstrating the expression of somatostatin receptors that are potential therapeutic targets. To date, only a few cerebellar metastases from PTC have been reported in the literature. PATIENT FINDINGS: We present an 82-year-old female, in whom an asymptomatic cerebellar metastasis from PTC was diagnosed by means of Tc-99m-EDDA/HYNIC-TOC scintigraphy four years after the initial diagnosis. She was previously treated with total thyroidectomy and regional lymph node dissection, followed by three cycles of radioiodine therapy. Despite persistently elevated thyroglobulin, no specific radioiodine accumulation was found in the whole body post-treatment scan. Tc-99m-EDDA/HYNIC-TOC scintiscan revealed foci of increased tracer uptake in the lungs, cervical lymph nodes, and a single focus in the head. Thus, therapy with octreotide LAR was initiated. The patient died four months later due to disseminated PTC. SUMMARY: In this paper, a patient with asymptomatic previously unknown non-iodine avid cerebellar metastasis of PTC diagnosed by means of scintigraphy using somatostatin analogue Tc-99m-EDDA/HYNIC-TOC is reported. CONCLUSIONS: Somatostatin receptor scintigraphy might be useful in the visualisation of non-iodine avid PTC metastases and demonstrat-ing the expression of somatostatin receptors that are potential therapeutic targets.

Application of positron emission tomography (PET/CT) in diagnosis of breast cancer. Part I. Diagnosis of breast cancer prior to treatment.

Positron emission tomography with computed tomography (PET/CT) is gaining popularity as a method for overall staging assessment of breast cancer. Currently, it is not a part of the routine workup before the beginning of treatment, because of insufficient sensitivity for the detection of small tumors (due to its limited spatial resolution), the heterogeneity of radiotracer uptake by the primary tumor, and unsatisfactory sensitivity in detection of lymph node metastases (particularly when they are small). Nevertheless, it should be considered when there is a high risk of metastases, because then initial PET/CT examination allows for accurate staging and may change the treatment algorithm in up to almost 50% of stage III patients, due to detection of distant and lymph node metastases throughout the whole body. Despite the discussed limitations of PET/CT, there is ongoing research concerning the recommendations for the examination prior to treatment. For a particular group of patients with high risk of metastases, PET/CT may be expected to become a part of the routine workup as the most appropriate staging method.

Peptide receptor radionuclide therapy of differentiated thyroid cancer: efficacy and toxicity.

In rare cases of differentiated thyroid carcinoma (DTC), radioiodine treatment is no longer effective due to cell dedifferentiation. Targeting somatostatin receptors in DTC cells by radiolabelled somatostatin analogues could provide an alternative therapy option. The aim of this study was to evaluate safety and efficacy of peptide receptor radionuclide therapy (PRRT) in patients with advanced, non-iodine avid DTC. Eleven patients aged 47-81 years (median: 65 years) with a history of several courses of radioiodine therapy, increasing thyroglobulin (Tg) and negative whole body scan, were qualified to the study. After confirming receptor expression by somatostatin receptor scintigraphy, PRRT with yttrium-90 labelled analogue was initiated. Fractionated treatment protocol was used with four doses of (90)Y-DOTA-TOC in 12-week intervals. Activity of each dose was 3.7 GBq (100 mCi). Of 11 patients, 5 died before receiving the fourth course of PRRT. In the remaining six patients, morphological response, evaluated 3 months after the last course using RECIST criteria showed partial remission (PR) in one patient, stable disease (SD) in two patients and progressive disease (PD) in three patients. Biochemical response based on Tg measurements before and after PRRT showed PR in one patient, SD in four patients and PD in one patient. Median survival was 21 months from the first course of PRRT. Only minor and transient hematological toxicity was observed in some patients. We conclude that PRRT is generally well-tolerated and may be a valuable option for some patients with radioiodine-refractory DTC.

The usefulness of standardized uptake value in differentiation between benign and malignant thyroid lesions detected incidentally in 18F-FDG PET/CT examination.

INTRODUCTION: In the last decade, (18)F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET and PET/CT) has become one of the major diagnostic tools used in oncology. A significant number of patients who undergo this procedure, due to non-thyroidal reasons, present incidental uptake of (18F-FDG) in the thyroid. The aim of the study was to compare the SUVmax (standardized uptake value) of thyroid focal lesions, which were incidentally found on PET/CT, in relation to the results of thyroid fine-needle aspiration biopsy (FNAB) and/or histopathological evaluation. MATERIALS AND METHODS: Patients referred for PET/CT examination, due to non-thyroidal illness, presented focal 18F-FDG uptake in the thyroid and were advised to undergo ultrasonography (US), hormonal evaluation, FNAB and/or total thyroidectomy at our institution. RESULTS: 6614 PET/CT examinations performed in 5520 patients were analyzed. Of the 122 patients with focal thyroid 18F-FDG activity, 82 patients (67.2%) underwent further thyroid evaluation using FNAB. Benign lesions were diagnosed in 46 patients, malignant - in 19 patients (confirmed by post-surgical histopathology), while 17 patients had inconclusive results of cytological assessment. Mean SUVmax of benign lesions was 3.2±2.8 (median = 2.4), while the mean SUVmax value for malignant lesions was 7.1±8.2 (median = 3.5). The risk of malignancy was 16.7% for lesions with a SUVmax under 3, 43.8% for lesions with a SUVmax between 3 and 6, and 54.6% for lesions with a SUVmax over 6. In the group of malignant lesions, a positive correlation between the lesion's diameter and SUVmax was observed (p = 0.03, r = 0.57). CONCLUSIONS: Subjects with incidental focal uptake of 18F-FDG in thyroid are at a high risk of thyroid malignancy. A high value of SUVmax further increases the risk of malignancy, indicating the necessity for further cytological or histological evaluation. However, as SUVmax correlated with the diameter of malignant lesions, small lesions with focal uptake of 18F-FDG should be interpreted cautiously.

Pyramidal lobe decreases endogenous TSH stimulation without impact on radio-iodine therapy outcome in patients with differentiated thyroid cancer.

OBJECTIVES: The aim of the study was to assess the frequency of pyramidal lobe (PL) detected in iodine-131 (I-131) scans of thyroid bed in patients after thyroidectomy for differentiated thyroid cancer (DTC) and to investigate influence of PL on endogenous thyrotropin (TSH) stimulation as well as on the effects of the radio-iodine ablation in one-year follow-up. PATIENTS AND METHODS: This study was designed as a retrospective analysis of 302 radio-iodine neck scans of patients thyroidectomized due to DTC. The study population was selected from patients with PL detected in thyroid bed scintigraphy. Patients without PL were included to the control group. The study and the control groups did not differ in age, sex of patients, histological type and stage of the DTC. RESULTS: Pyramidal lobes were found in 30.5% of all patients. Patients in the study group underwent repeat surgery more often than controls without PL. Preablative TSH level in patients with PL was statistically lower than in the control group, in contrast to free thyroid hormones, which were higher in patients with PL. Preablative and postablative TSH-stimulated thyroglobulin (Tg) and antibodies against thyroglobulin (TgAbs) were measured in both groups, and comparison did not reveal differences. Moreover, for the per-patient analysis, sites of uptake in whole body scintigraphy performed 1 year after radio-iodine remnant ablation (RRA) did not differ between the study and the control groups. CONCLUSION: Pyramidal lobe decreases endogenous TSH stimulation without impact on radio-iodine therapy outcome in patients with DTC.

Iodine-131 for therapy of thyroid diseases. Physical and biological basis.

Iodine-131 is successfully used in the treatment of hyperthyroidism and differentiated thyroid cancer. Thyroid is the critical organ for iodine. Iodine is taken up by the thyroid follicular cells. Radioactive isotope iodine-131 simultaneously emits two types of radiation: radiation beta minus (ß-) used for the treatment and gamma (γ) used for diagnosis. Due to the penetration of beta particles in tissue, damaging effect of ß-radiation is restricted to thyroid cells. In this article, characteristic of iodine-131, mechanism of action and mechanism of tissue damage is presented. HIGH energy γ-ray emission, contributes to the dose of both: patient's body and the personnel. In accordance with the principles of radiation protection, reducing exposure to ionizing radiation should be achieved by: use of proper shieldings, organization of work, appropriate distance from the radiation source and reducing the time of exposure. Treatment with I-131, depending on medical indications, may be carried out on stationary or outpatient basis. All activities conducted in the exposure to radiation must comply with the principles of radiation protection, in accordance with the applicable regulations, that are also presented in this article.