Radioactive iodine treatment of metastatic thyroid carcinoma with clinical thyrotoxicosis

We present a case of well-differentiated follicular carcinoma of the thyroid with hyperfunctioning metastases and clinical thyrotoxicosis. The recommended I-131 treatment dose for patients with widespread bone metastases from thyroid carcinoma is 200 mCi. However, in a patient with hyperfunctioning metastatic tumor and increased radioiodine uptake, the treatment dose should be modified. Radiation dosimetry measurements performed on the patient in this study demonstrated that 132 mCi would be a safe therapeutic I-131 dose which would avoid injury to normal radiosensitive tissues. Consequently, she was given a 130-mCi therapeutic dose.     

Absence of thyroid stunning after diagnostic whole-body scanning with 185 MBq 131I.

There has been recent controversy regarding the optimal protocol for imaging and ablation of post-thyroidectomy patients. Several authors have suggested that a scanning dose of 185-370 MBq (5-10 mCi) (131)I may be capable of producing a stunning effect on thyroid tissue that may interfere with the uptake and efficacy of the subsequent ablation dose of radioiodine. The purpose of this study was to determine whether a 185-MBq (5 mCi) diagnostic dose of (131)I produces a visually apparent stunning effect 72 h before (131)I ablation therapy. METHODS: One hundred twenty-two consecutive post-thyroidectomy patients for differentiated thyroid carcinoma received a 185-MBq (5 mCi) diagnostic dose of (131)I followed by a whole-body diagnostic scan at 72 h. On the same day the diagnostic scan was completed, the patient was admitted to the hospital and received an (131)I ablation therapy dose of 5550 MBq (150 mCi) in most cases. A postablation, whole-body scan was obtained at 72 h and compared with the previous diagnostic scan for any visual evidence of stunning. RESULTS: No cases of visually apparent thyroid stunning were observed on any of the postablation scans with regard to the number of (131)I foci identified or the relative intensity of (131)I uptake seen. CONCLUSION: Diagnostic whole-body scanning can be performed effectively with a 185-MBq (5 mCi) dose of (131)I 72 h before radioiodine ablation without concern for thyroid stunning.     

Differentiated thyroid cancer presenting with thyrotoxicosis due to functioning metastases

Thyrotoxicosis due to functioning metastases in differentiated thyroid cancer (DTC) is exceedingly rare. We report a case of follicular carcinoma in a 54-year-old manager, who presented with thyrotoxicosis, shortness of breath and lung metastases. Transbronchial biopsy of a pulmonary nodule demonstrated normal thyroid. This was interpreted as representing very well-differentiated thyroid cancer. CT, (131)I whole-body imaging and dosimetry is described following total thyroidectomy and repeated radioiodine administration (cumulative activity 34.6 GBq). The patient became asymptomatic with almost complete eradication of the pulmonary metastases. Potential complications of thyroid storm, bone marrow failure and pulmonary fibrosis following radioiodine are discussed, together with methods to minimise these risks.     

Measuring the actual I-131 thyroid uptake curve with a collar detector system: a feasibility study

Radionuclide therapy using I-131 is commonly used for the treatment of benign thyroid diseases. The therapeutic dose to be administered is calculated based on the type of disease, the volume of the thyroid, and the measured uptake percentage. This methodology assumes a similar biological half-life of iodine, whereas in reality a large variation in biological half-life is observed. More knowledge about the actual biological half-life of iodine for individual patients will improve the quantification of the delivered radiation dose during radioiodine therapy and could aid the evaluation of the success of the therapy. In this feasibility study we used a novel measurement device [Collar Therapy Indicator (CoTI)] to measure the uptake curve of patients undergoing I-131 radioiodine therapy. The CoTI device is a light-weight wearable device that contains two independent gamma radiation detectors that are placed in a collar. By comparing results of thyroid uptake measurements with results obtained with a gamma camera, the precision of the system is demonstrated. Additionally, for three patients the uptake curve is measured during 48 h of admission in the hospital. The presented results demonstrate the feasibility of the new measurement device to measure the uptake curve during radioiodine therapy.     

Pelvic radioiodine uptake in a rectal wall teratoma after thyroidectomy for papillary carcinoma.

A 30-yr-old woman with previously resected papillary thyroid carcinoma was found to have a pelvic lesion which concentrated radioiodine. By performing simultaneous 131I whole-body and 99mTc-methylene diphosphonate bone scans, we found the lesion to be in soft tissue between the sacrum and bladder. Radioiodine therapy was postponed so that the lesion, a benign teratoma of the rectal wall, could be surgically removed. Prior to laparotomy, the patient received a second tracer dose of 131I so that the lesion could be located at surgery with a hand-held gamma detector. A postoperative whole-body 131I scan confirmed that the lesion had been removed, thus reducing the absorbed radiation that would have been received by the ovaries during radioiodine therapy. Although the lesion contained both thyroid and gastric epithelium, accumulated 131I was limited to the area with thyroid follicles.     

Radionuclide therapy of the thyroid

Radionuclide therapy has a proven place in the management of patients with thyroid disease. Iodine-131 therapy has been established as both successful and safe in treating patients with thyrotoxicosis and thyroid malignancy. Protocols for patient treatment are now standardised, although some variation in practice exists across Europe. There remains much confusion as to which patients should be selected for treatment with radio-iodine for thyrotoxicosis and what dose should be administered. A review of the literature reveals that many of the theoretical hazards of treatment with radioiodine have not been encountered despite many years of usage. New therapies for medullary thyroid cancer are now being evaluated and recent promising developments are discussed in detail.     

Procedure guidelines for radioiodine therapy of differentiated thyroid cancer (version 3)

The procedure guideline for radioiodine therapy (RIT) of differentiated thyroid cancer (version 3) is the counterpart to the procedure guideline for (131)I whole-body scintigraphy (version 3) and specify the interdisciplinary guideline for thyroid cancer of the Deutsche Krebsgesellschaft concerning the nuclear medicine part. Recommendation for ablative (131)I therapy is given for all differentiated thyroid carcinoma (DTC) >1 cm. Regarding DTC < or =1 cm (131)I ablation may be helpful in an individual constellation. Preparation for (131)I ablation requires low iodine diet for two weeks and TSH-stimulation by withdrawal of thyroid hormone medication or by use of recombinant human TSH (rhTSH). The advantages of rhTSH (no symptoms of hypothyroidism, lower blood activity) and the advantages of endogenous TSH-stimulation (necessary for (131)I-therapy in patients with metastases, higher sensitivity of (131)I whole-body scan) are discussed. In most centers standard activities are used for (131)I ablation. If pretherapeutic dosimetry is planned, the diagnostic administration of (131)I should not exceed 1-10 MBq, alternative tracers are (123)I or (124)I. The recommendations for contraception and family planning are harmonized with the recommendation of ATA and ETA. Regarding the best possible protection of salivary glands the evidence is insufficient to recommend a specific setting. To minimize the risk of dental caries due to xerostomia patients should use preventive strategies for dental hygiene.     

False-positive uptake of I-131 in a laryngocele mimicking thyroid remnant after thyroidectomy for papillary thyroid carcinoma

A 66-year-old woman underwent total thyroidectomy for papillary thyroid carcinoma stage pT4 followed by radioiodine therapy with 3.7 GBq (100 mCi) iodine-131. Radioiodine therapy revealed intense radioiodine uptake of the neck, which was interpreted as thyroid remnant tissue. Follow-up whole-body scans with iodine-131 in hypothyroidism 3 months and 1 year after radioiodine therapy revealed focal uptake in the neck. Computed tomography and gadolinium-enhanced MRI of the neck demonstrated an ovoid lesion in the larynx without gadolinium enhancement. Neither thyroid remnant tissue nor enlarged cervical lymph nodes could be demonstrated either on CT or on MRI. Further examination of the patient in the ear, nose and throat department confirmed the finding of a laryngocele and biopsies demonstrated benign tissue. Follow-up whole-body scans with iodine-131 in hypothyroidism 3 years and after injection of rhTSH 5 years after radioiodine therapy reproduced the focal uptake in the neck. After initial radioiodine therapy thyroglobulin levels were never measurable, not at any of the whole-body scans in hypothyroidism, after rhTSH, or at intermediate follow-up examinations under TSH-suppressive levothyroxine therapy. The patient declined definitive operative revision of the laryngocele and is in good health 8 years after the diagnosis of papillary thyroid carcinoma.     

Evaluation of dosimetry of radioiodine therapy in benign and malignant thyroid disorders by means of iodine-124 and PET

The aim of this study was to evaluate the use of 124I positron emission tomography (PET) to determine the dosimetry of radioiodine therapy in hyperthyroidism and thyroid cancer. Phantom studies to assess the accuracy of PET were performed using an EEC phantom with spheres of different diameters filled with 3-30 MBq of 124I. Patient dosimetry was derived from PET data obtained 1-13 days after simultaneous oral administration of a therapeutic dose of 131I and a diagnostic dose of 124I. The obtained data were compared with findings from intratherapeutic probe measurements and clinical outcome. The phantom studies confirmed that 124I can be quantitated by PET (imprecision < or =10%), and volumetry is feasible for nodules <13 mm (imprecision < or =20%). Any influence of contamination with 123I or the simultaneous administration of 131I on the accuracy of the PET quantification and the probe measurements was ruled out by phantom measurements with solutions of 131I, 124I and 123I in various ratios. In autonomous nodular goitres, radioiodine uptake measured by PET varied from 25.4% to 64.3% and was not significantly different from that obtained by a scintillation probe (24.1%-73.1%, correlation coefficient r=0.91). Comparison of uptake and effective half-life in normal tissue versus autonomous nodules revealed significant differences in uptake but not in effective half-life [uptake 2.0-8.3 kBq/(ml x MBq) in normal tissue vs 12.6-29.3 kBq/(ml x MBq) in nodules; half-life 97.8-156.7 h in normal tissue vs 73.3-192.3 h in nodules]. Calculated radiation doses ranged between 177 and 633 Gy for autonomous nodules and between 47 and 126 Gy for normal tissue. In thyroid cancer patients, doses between 350 and 1,420 Gy were achieved in thyroid remnants and between 70 and 170 Gy in tumour metastases. It is concluded that 124I and PET are suitable for evaluation of the dosimetry of radioiodine therapy in benign and malignant thyroid diseases. The applied technique might be particularly useful for quantitative dose-response studies in radioiodine treatment and further investigations of stunning phenomena.     

Patient dosimetry for 131I-lipiodol therapy

Patient dosimetry data for intra-arterial()iodine-131 lipiodol therapy for hepatocellular carcinoma (HCC) are scarce. The aim of this study was to determine the absorbed dose (D) to the tumour and healthy tissues, as well as the effective dose (E), by different methods for 17 therapies in 15 patients who received a mean activity of 1.9 GBq (SD 0.2) (131)I-lipiodol. Eight patients received thyroid blocking by potassium iodide (KI). Patient dosimetry was performed based on bi-planar total body scans using the Monte Carlo simulation program MCNP-4B and the MIRDOSE-3 standard software program. CT images of each patient were used to determine liver and tumour volume and position. The total body dose to the patient was also determined by biological dosimetry with the in vitro micronucleus (MN) assay. From the increase in micronucleus yield after therapy, the equivalent total body dose (ETBD) was calculated. Results for D and E were comparable between MCNP and MIRDOSE (liver: mean 7.8 Gy, SD 1.8, lungs: 6.8 Gy, SD 2.9, E: 2.01 Gy, SD 0.58). MIRDOSE gave a systematic overestimation for the tumour dose, especially for tumours <3 cm (15%). The MCNP method is more accurate since the dose contributions from tumour to organs and vice versa can be accounted for. The absorbed dose to the thyroid was significantly lower for patients who received KI (7.2 Gy, SD 2.2) than for the other patients (13.8 Gy, SD 5.0). MN yields could be obtained for only 12 of the 17 therapies due to hypersplenism. A mean ETBD of 1.66 Gy (SD 0.73) was obtained, but the MN results showed no correlation between the ETBD and the total body dose values of the physical dosimetry. Also, in all except one of the patients, no further reduction in the number of thrombocytes was observed after therapy, probably due to the existing hypersplenism. It is concluded that in view of the high E values, patient dosimetry is necessary for patients receiving (131)I-lipiodol therapy. Except in the case of the smaller tumours, comparable results were obtained with MCNP and MIRDOSE. Due to hypersplenism, biological dosimetry results based on the MN assay are not reliable.     

A pragmatic protocol for I-131 rhTSH-stimulated ablation therapy in patients with renal failure

PURPOSE: Ablation of thyroid remnants in patients with differentiated thyroid carcinoma and renal failure can be challenging because of the altered and variable clearance rates of iodine from the blood secondary to variations in dialysis protocols, which complicate the selection of the appropriate I-131 dose. The advent of recombinant human TSH allows a simpler approach to dosimetry and ablation without rendering the patient hypothyroid. Avoidance of hypothyroidism may be an important consideration for patients who are experiencing various morbidities from conditions associated with renal failure. METHOD: Three patients on dialysis, who had undergone total thyroidectomy and were euthyroid on L-thyroxine replacement, were given diagnostic doses of I-131 followed by blood and whole-body retention measurements through serial dialyses to determine individual blood clearance rates. After administration of rhTSH, each patient received an ablative dose of I-131 calculated to keep total body dose below 1 Gy. RESULTS: The treatments were administered without complications, and in follow-up imaging of 2 available patients, the ablations were demonstrated to be complete. CONCLUSION: Dosimetry performed on euthyroid dialysis patients permits I-131 dose selection and avoids the additional morbidity of hypothyroidism.     

Differentiated thyroid cancer: radioiodine following lobectomy - a clinical feasibility study

The surgical management of differentiated thyroid cancer remains controversial. Total thyroidectomy has been associated with higher rates of post-operative morbidity than more conservative surgery, but radioiodine ablation of residual thyroid tissue is considered to be particularly difficult after lobectomy. The purpose of this retrospective study was to assess the feasibility of 131I ablation after lobectomy, compared with total thyroidectomy, in patients who had undergone surgery for differentiated thyroid carcinoma. A retrospective analysis was performed of 225 post-surgical thyroid cancer patients treated with 3500 MBq 131I for the ablation of thyroid remnants. One hundred and sixty-five patients (73%) had previously undergone total thyroidectomy, whilst 60 patients (27%) had been treated by lobectomy. All patients underwent diagnostic scintigraphy, with 40 MBq 131I, 2 days prior to ablative therapy and at 3 months post-ablation. The median pre-ablative 131I neck uptake values were 3.3% and 20.1% in patients treated by total thyroidectomy and lobectomy, respectively (P < 0.001). Pre-ablation neck uptake correlated strongly with the whole-body 131I burden 2 days after 131I therapy (P < 0.001), and the biological half-life of the radioiodine was markedly longer after lobectomy than after total thyroidectomy. Ninety-eight per cent of patients treated by total thyroidectomy were successfully ablated by one 131I treatment, compared with 90% after lobectomy (P < 0.05). There were no significant differences in 131I neck uptake or serum thyroglobulin levels between the two patient groups at 3 months post-ablation. These data show that high rates of thyroid ablation can be achieved with a single fixed dose of 131I after thyroid lobectomy. The use of this surgical procedure may result in a longer period of patient isolation than that required after total thyroidectomy. However, the clear correlation between pre-ablation neck uptake and 131I burden at 2 days post-therapy enables effective treatment scheduling, so making lobectomy followed by 131I ablation a practical option for the management of differentiated thyroid cancer.     

Dosimetry of iodine 131 metaiodobenzylguanidine for treatment of resistant neuroblastoma: results of a UK study

In 1987, the United Kingdom Children's Cancer Study Group (UKCCSG) set up a multi-centre study to investigate the toxicity of iodine 131 metaiodobenzylguanidine (mIBG) in the treatment of resistant neuroblastoma. Since December 1987, 25 children suffering from neuroblastoma have been treated with 131I-mIBG at six UK centres. All centres followed standardised physics and clinical protocols to provide consistent toxicity and dosimetry data. These protocols describe the methods employed for both the tracer study using 131I-mIBG and the subsequent therapy. Whole-body dosimetry calculations were performed on data from the tracer study. The activity administered for therapy was the amount predicted to deliver a predefined whole-body dose. Estimates of doses delivered to various organs during treatment are given in Table 1.     

Dosimetry study in patients with autonomous thyroid nodule who are candidates for radioiodine therapy.

A dosimetry study was performed on 26 patients with an autonomous thyroid nodule and suppressed serum thyroid-stimulating hormone, to determine the dose to extranodular tissue when the nodule receives 300 Gy for 131I therapy. METHODS: Parameters of radioiodine turnover to be used in the dosimetry formula were separately obtained for the nodule and the contralateral lobe, as a measurable example of the extranodular tissue, using 55 MBq 123I and a computer-assisted gamma camera. The biologic half-life of 123I was then converted into the effective half-life of 131I, and the volumes of the nodule and the lobe were obtained by scintigraphy or sonography. RESULTS: The mean dose to the contralateral lobe from uptake and irradiation by the nodule was calculated to be 32 Gy, and that to the ipsilateral lobe was estimated to be 34 Gy. CONCLUSION: During radioiodine therapy for autonomous thyroid nodules, the extranodular tissue receives a higher dose than is generally assumed, which explains the relatively high rate of post-treatment hypothyroidism reported in the literature.     

Lung dosimetry for radioiodine treatment planning in the case of diffuse lung metastases.

The lungs are the most frequent sites of distant metastasis in differentiated thyroid carcinoma. Radioiodine treatment planning for these patients is usually performed following the Benua-Leeper method, which constrains the administered activity to 2.96 GBq (80 mCi) whole-body retention at 48 h after administration to prevent lung toxicity in the presence of iodine-avid lung metastases. This limit was derived from clinical experience, and a dosimetric analysis of lung and tumor absorbed dose would be useful to understand the implications of this limit on toxicity and tumor control. Because of highly nonuniform lung density and composition as well as the nonuniform activity distribution when the lungs contain tumor nodules, Monte Carlo dosimetry is required to estimate tumor and normal lung absorbed dose. Reassessment of this toxicity limit is also appropriate in light of the contemporary use of recombinant thyrotropin (thyroid-stimulating hormone) (rTSH) to prepare patients for radioiodine therapy. In this work we demonstrated the use of MCNP, a Monte Carlo electron and photon transport code, in a 3-dimensional (3D) imaging-based absorbed dose calculation for tumor and normal lungs. METHODS: A pediatric thyroid cancer patient with diffuse lung metastases was administered 37 MBq of (131)I after preparation with rTSH. SPECT/CT scans were performed over the chest at 27, 74, and 147 h after tracer administration. The time-activity curve for (131)I in the lungs was derived from the whole-body planar imaging and compared with that obtained from the quantitative SPECT methods. Reconstructed and coregistered SPECT/CT images were converted into 3D density and activity probability maps suitable for MCNP4b input. Absorbed dose maps were calculated using electron and photon transport in MCNP4b. Administered activity was estimated on the basis of the maximum tolerated dose (MTD) of 27.25 Gy to the normal lungs. Computational efficiency of the MCNP4b code was studied with a simple segmentation approach. In addition, the Benua-Leeper method was used to estimate the recommended administered activity. The standard dosing plan was modified to account for the weight of this pediatric patient, where the 2.96-GBq (80 mCi) whole-body retention was scaled to 2.44 GBq (66 mCi) to give the same dose rate of 43.6 rad/h in the lungs at 48 h. RESULTS: Using the MCNP4b code, both the spatial dose distribution and a dose-volume histogram were obtained for the lungs. An administered activity of 1.72 GBq (46.4 mCi) delivered the putative MTD of 27.25 Gy to the lungs with a tumor absorbed dose of 63.7 Gy. Directly applying the Benua-Leeper method, an administered activity of 3.89 GBq (105.0 mCi) was obtained, resulting in tumor and lung absorbed doses of 144.2 and 61.6 Gy, respectively, when the MCNP-based dosimetry was applied. The voxel-by-voxel calculation time of 4,642.3 h for photon transport was reduced to 16.8 h when the activity maps were segmented into 20 regions. CONCLUSION: MCNP4b-based, patient-specific 3D dosimetry is feasible and important in the dosimetry of thyroid cancer patients with avid lung metastases that exhibit prolonged retention in the lungs.     

131I治疗Graves甲状腺功能亢进症中碳酸锂的应用

131I治疗Graves甲状腺功能亢进症(甲亢)的有效性取决于其在甲状腺内的滞留时间,且受治疗前抗甲状腺药物使用、肿大甲状腺容积和甲状腺24 h摄碘率等因素的影响.锂具有阻止有机碘和甲状腺激素自甲状腺内释出的作用而不影响甲状腺对131I的摄取,因此,131I治疗Graves甲亢前后辅以短程、小剂量碳酸锂,具有提高甲状腺...     

Nasolacrimal drainage obstruction after radioiodine therapy: case report and a review of the literature

The authors report a 54-year-old woman with papillary thyroid carcinoma (Lindsay type, pT2 N0 M1) with pulmonary metastases. After a total thyroidectomy, a series of 3 radioiodine therapies were performed with a cumulative dose of 700 mCi I-131. After termination of the therapy, the patient was initially without complaints, but approximately 6 months later, epiphora was noted, first only of the right eye and eventually of both eyes. A whole-body I-131 scan performed 1 year after final radioiodine therapy showed atypical tracer accumulation in both medial orbital regions. This finding was new compared with the scan that was done 1 year before. Dacryocystography revealed bilateral occlusion of the lacrimal drainage system. A review of the literature shows that epiphora and lacrimal duct alterations are rarely investigated and potentially underestimated side effects after high-dose radioiodine therapy.     

Radioiodine therapy of thyroid autonomy

Over half a century, treatment of thyroid autonomy with an oral dose of iodine-131 has proven to be effective. The optimum management strategy for the patient is, however, still a matter of debate. The article provides an overview of the pathogenesis of functional autonomy and its clinical relevance. According to the guidelines on both sides of the Atlantic, radioiodine treatment is considered the most comfortable and economical approach to the treatment of the toxic nodular goitre. Some differences in the preparation procedures in the guidelines of the American and the German Society of Nuclear Medicine are discussed with respect to therapy results and the subtypes of thyroid autonomy. The results of studies are summarised concerning changes in thyroid function and thyroid volume after a course of radioiodine treatment. Therapy-related risks, such as immunogenic hypothyroidism or thyroid cancer, are discussed. (131)I treatment of functional autonomy and hyperthyroidism is considered an effective and safe procedure.     

Radiotherapy with iodine-131 in recurrent malignant struma ovarii

Malignant struma ovarii is a very rare disease and, therefore, there is neither common agreement on treatment regimens nor sufficient follow-up experience. We present a case of a 49-year-old woman with malignant struma ovarii of the follicular type, who received ablative radioiodine treatment after thyroidectomy and surgical removal of the primary tumour. During followup examinations an increasing thyroglobulin level was found, caused by a tumour relapse with suspected urinary bladder infiltration on CT and proven uptake of radioiodine on whole-body scanning with iodine-131. After administration of 6 GBq¹³¹I, complete tumour regression was achieved with no evidence of a new relapse during a 30-month follow-up period. Correspondingly, repeated thyroglobulin measurements were all negative. This case demonstrates the benefit of combined surgical and radioiodine treatment of malignant struma ovarii for both monitoring and therapy of relapse or metastases; thus, the same therapeutic regimen as is employed in primary differentiated thyroid carcinoma may be recommended.