The SNMMI Practice Guideline for Therapy of Thyroid Disease with 131I 3.0

Current controversies and future directions in the diagnosis and management of differentiated thyroid cancers

Despite the development of novel diagnostic, surgical, and chemotherapeutic approaches to differentiated thyroid cancers (DTCs), the diagnosis and management of these tumors remains controversial. The most recent American Thyroid Association (ATA) guidelines, released in 2015, reflect a recent shift towards less aggressive management for patients with DTCs. However, many clinicians have expressed concern that more conservative management will put patients at risk for disease recurrence and metastasis. In particular, the management of indeterminate nodules on fine needle aspiration (with special attention to genetic and epigenetic markers of malignancy), the extent of surgery for known differentiated cancers, the role of adjuvant radioactive iodine (RAI) therapy, and novel targeted treatments with tyrosine kinase inhibitors (TKIs) represent current areas of uncertainty and opportunities for future research. In this review, we examine the current state of the art in these areas, and address some of the questions that remain.

Treatment of adult Graves' disease

Treatment strategy in Graves' disease firstly requires recovery of euthyroid status by antithyroid therapy. Treatment modalities, precautions, advantages and side-effects are to be discussed with the patient. No particular treatment modality has demonstrated superiority. Pregnancy or pregnancy project affects choice of treatment and monitoring. Graves' orbitopathy is liable to be aggravated by iodine-131 treatment and requires pre-treatment assessment. Iodine-131 treatment aims at achieving hypothyroidism. Thyroid surgery for Graves' disease should preferably be performed by an expert team. In case of recurrence of hyperthyroidism, the various treatment options should be discussed with the patient. Empiric treatment of thyroid dermopathy uses local corticosteroids in occlusive dressing.

Initial Clinical Investigation of [18F]Tetrafluoroborate PET/CT in Comparison to [124I]Iodine PET/CT for Imaging Thyroid Cancer

AIM

Recently, [F]tetrafluoroborate ([F]TFB) has been introduced as a versatile PET probe for imaging the human sodium/iodide symporter activity. This pilot study aimed to compare [F]TFB-PET/CT with [I]NaI-PET/CT imaging in thyroid cancer patients.

METHODS

Nine patients with newly diagnosed differentiated thyroid cancer underwent both [F]TFB- and [I]NaI-PET/CT after total thyroidectomy. PET/CT scans were visually analyzed for the presence of remnant thyroid tissue and for metastatic lesions on a patient and lesion basis. For semiquantitative analysis, thyroid remnant/tumor to blood pool ratios were calculated.

RESULTS

All patients presented with positive [F]TFB and [I]NaI-PET/CT scans. Retention of I in remnant thyroid tissue was significantly higher as compared with [F]TFB (P < 0.01). In a lesion-based analysis, both tracers identified an almost equal number of foci with [F]TFB depicting a total of 41 foci and I a total of 40 foci, respectively. In 6 of 9 patients, both radiopharmaceuticals returned an identical number of foci. Two I-positive benign thyroid remnants were missed by [F]TFB-PET/CT in a single patient. In another case, both tracers identified different thyroid remnant tissues in the cervical region. Notably, [F]TFB demonstrated additional (I-negative) cervical lymph node metastases in 2 patients, leading to an overall agreement between the radiotracers of 91% (74/81 foci).

DISCUSSION

In this pilot study, [F]TFB-PET was not inferior to [I]NaI-PET for detecting thyroid cancer and its metastases and was able to detect [I]NaI-PET-negative viable differentiated thyroid cancer metastases. Further clinical evaluation as a PET tracer for imaging thyroid pathophysiology and human sodium/iodide symporter expressing neoplasms is highly warranted.

Use of radioiodine-131 scan to measure influence of surgical discipline, practice, and volume on residual thyroid tissue after total thyroidectomy for differentiated thyroid carcinoma

BACKGROUND

Our study's purpose is to determine the influence of surgical discipline, surgeon site, and volume on remnant thyroid tissue visualized on radioactive iodine-131 (I-131) scans after total thyroidectomy and I-131 ablation in patients with well-differentiated thyroid carcinomas.

METHODS

We retrospectively reviewed all cases of patients who received I-131 therapeutic ablation and postablation radioactive I-131 scans at our center after thyroidectomy to calculate the fraction of administered dose multiplied by 1000 (UDR1000).

RESULTS

The remnant thyroid tissue (ie, the UDR1000), between academic and community surgeons was 0.471 (±0.705) and 1.190 (±2.487), respectively (P = .001). The UDR1000 between otolaryngology-head and neck surgery and general surgery was 0.654 (±1.575) and 1.043 (±1.625), respectively (P = .159). The UDR1000 partitioned by patient frequencies of <10, 10 to 19, and ≥20 patients yielded 1.255 (±2.554), 0.926 (±2.084), and 0.467 (±0.721), respectively (P = .003).

CONCLUSION

Our study found statistically significant differences in residual thyroid tissue visualized on radioactive I-131 scans based on surgeon parameters.

Selected Radiation Safety Aspects Including Transportation and Lodging After Outpatient 131I Therapy for Differentiated Thyroid Cancer

BACKGROUND

Whether radioactive iodine (¹³¹I) treatments for differentiated thyroid cancer should be performed as an outpatient or inpatient remains controversial. The objective of this study was to survey selected aspects of radiation safety of patients treated with ¹³¹I for differentiated thyroid cancer as an outpatient.

METHODS

An e-mail invitation was sent to over 15,000 members of ThyCa: Thyroid Cancer Survivors' Association, Inc. to complete a web-based survey on selected aspects of radiation safety regarding their last outpatient ¹³¹I treatment.

RESULTS

A total of 1549 patients completed the survey. Forty-five percent (699/1541) of the respondents reported no discussion on the choice of an inpatient or outpatient treatment. Moreover, 5% (79/1541) of the respondents reported that their insurance company made the decision. Survey respondents recalled receiving oral and written radiation safety instructions 97% (1459/1504) and 93% (1351/1447) of the time, respectively. Nuclear medicine physicians delivered oral and written instructions to 54% (807/1504) and 41% (602/1462) of the respondents, respectively. Eighty-eight percent (1208/1370) of the respondents were discharged within 1 hour after receiving their ¹³¹I treatment, and 97% (1334/1373) traveled in their own car after being released from the treating facility. Immediately post-therapy, 94% (1398/1488) of the respondents stayed at their own home or a relative's home, while 5% (76/1488) resided in a public lodging. The specific recommendations received by patients about radiation precautions varied widely among the respondents. Ninety-nine percent (1451/1467) of the respondents believed they were compliant with the instructions.

CONCLUSION

This is the largest, patient-based survey published regarding selected radiation safety aspects of outpatient ¹³¹I treatment. This survey suggests several concerns about radiation safety, such as the decision process regarding inpatient versus outpatient treatment, instructions about radiation safety, transportation, and lodging after radioiodine therapy. These concerns warrant further discussion, guidelines, and/or policies.

Reproducibility of radioactive iodine uptake (RAIU) measurements

Background

Measurement of radioactive iodine uptake (RAIU) is an important aspect of the assessment and treatment of patients with hyperthyroidism. Its uncertainty affects how much of a true change in RAIU can be detected as well as appropriateness of the therapy dosage upon which it is based. In this study, a method of estimating the reproducibility and least significant change (LSC) values for RAIU measurements, and the implications of the values observed are discussed, with emphasis on application to quality assurance initiatives.

Methods

We prospectively studied 36 consecutive patients referred for RAIU measurements. Twenty‐four hours after oral administration of 370 kBq of ¹³¹I‐NaI in capsule form, RAIU measurements were obtained in duplicate using a thyroid probe uptake system. Assessment of reproducibility was performed using root‐mean‐square standard deviation.

Results

Average difference between duplicated RAIU measurements in our study cohort was −0.1 ± 1.6% and ranged from −4.8% to 3.1%. Reproducibility of probe‐based RAIU measurement was calculated to be 1.1% and 95% LSC was 3.2%.

Conclusion

In our clinic, probe‐based RAIU is a reproducible and relatively precise measurement. Using the method we have outlined, each institution can perform reproducibility assessment and compute the LSC of RAIU measurements based on its own staff, iodine isotope, equipment, protocols, and patient population. These values are useful in the assessment of serial change in RAIU, and as more experience is accumulated, can serve as benchmarks to be used in quality assurance initiatives.

Dosing of radioactive iodine in end-stage renal disease patient with thyroid cancer

We describe detailed administration of thyroidal and extrathyroidal doses of radioiodine to a patient with end-stage renal disease on hemodialysis. A thorough description of area under curve measurements in a patient with compromised renal function has rarely been described in the literature. Few publications have described thyroid cancer management of patients on hemodialysis, and we believe our management will aid in patient treatment in the future.

Dosimetry-based treatment planning for molecular radiotherapy: a summary of the 2017 report from the Internal Dosimetry Task Force

BACKGROUND

The European directive on basic safety standards (Council directive 2013/59 Euratom) mandates dosimetry-based treatment planning for radiopharmaceutical therapies. The directive comes into operation February 2018, and the aim of a report produced by the Internal Dosimetry Task Force of the European Association of Nuclear Medicine is to address this aspect of the directive. A summary of the report is presented.

RESULTS

A brief review of five of the most common therapy procedures is included in the current text, focused on the potential to perform patient-specific dosimetry. In the full report, 11 different therapeutic procedures are included, allowing additional considerations of effectiveness, references to specific literature on quantitative imaging and dosimetry, and existing evidence for absorbed dose-effect correlations for each treatment. Individualized treatment planning with tracer diagnostics and verification of the absorbed doses delivered following therapy is found to be scientifically feasible for almost all procedures investigated, using quantitative imaging and/or external monitoring. Translation of this directive into clinical practice will have significant implications for resource requirements.

CONCLUSIONS

Molecular radiotherapy is undergoing a significant expansion, and the groundwork for dosimetry-based treatment planning is already in place. The mandated individualization is likely to improve the effectiveness of the treatments, although must be adequately resourced.

Gamma camera based method for 131I capsule counting: an alternate method to Uptake probe method

The main objective of this study was to check the validity of using gamma camera as an alternate method to thyroid uptake probe, for counting 25uCi (0.925 MBq) and 50uCi (1.85 MBq) 131I capsules before administration to thyroid patients. Methods: - 10 sets each of 25uCi (0.925 MBq) and 50uCi (1.85 MBq) 131I capsules received from Board Of Radiation and Isotope Technology, Department Of Atomic Energy, India (BRIT, DAE) have been counted individually using thyroid uptake probe for 10 seconds following institutional protocol and also by keeping individual capsule of a set with 8cm gap between each of them .These capsules were also scanned by Scintillation gamma camera for 100 seconds. Capsules having counts within the range of mean ±2 Standard Deviation (SD) were accepted for patient administration. After analysing both the data, correlation coefficient between these two methods has been evaluated. Results: Scanned images were analysed by drawing Identical ROI around each set of 25uCi (0.925 MBq) and 50uCi (1.85 MBq) 131I capsules. Capsules with counts within 2 Standard Deviation from mean were accepted for patient administration. Good correlation coefficient (r >0.95) was observed between these two counts set. Conclusion: Gamma camera based 131I -capsule counting method is an easy and time saving method compared to probe based capsule counting method as we can scan a set of capsules in a single acquisition. It can provide uniformity information for a batch of 131I -capsules and avoid the time consuming method of individual capsule counting with the thyroid uptake probe.

Quantitative Imaging for Targeted Radionuclide Therapy Dosimetry - Technical Review

Targeted radionuclide therapy (TRT) is a promising technique for cancer therapy. However, in order to deliver the required dose to the tumor, minimize potential toxicity in normal organs, as well as monitor therapeutic effects, it is important to assess the individualized internal dosimetry based on patient-specific data. Advanced imaging techniques, especially radionuclide imaging, can be used to determine the spatial distribution of administered tracers for calculating the organ-absorbed dose. While planar scintigraphy is still the mainstream imaging method, SPECT, PET and bremsstrahlung imaging have promising properties to improve accuracy in quantification. This article reviews the basic principles of TRT and discusses the latest development in radionuclide imaging techniques for different theranostic agents, with emphasis on their potential to improve personalized TRT dosimetry.

18F-Tetrafluoroborate, a PET Probe for Imaging Sodium/Iodide Symporter Expression: Whole-Body Biodistribution, Safety, and Radiation Dosimetry in Thyroid Cancer Patients

We report the safety, biodistribution, and internal radiation dosimetry, in humans with thyroid cancer, of 18F-tetrafluoroborate (18F-TFB), a novel PET radioligand for imaging the human sodium/iodide symporter (hNIS). Methods: Serial whole-body PET scans of 5 subjects with recently diagnosed thyroid cancer were acquired before surgery for up to 4 h after injection of 184 ± 15 MBq of 18F-TFB. Activity was determined in whole blood, plasma, and urine. Mean organ-absorbed doses and effective doses were calculated via quantitative image analysis and using OLINDA/EXM software. Results: Images showed a high uptake of 18F-TFB in known areas of high hNIS expression (thyroid, salivary glands, and stomach). Excretion was predominantly renal. No adverse effects in relation to safety of the radiopharmaceutical were observed. The effective dose was 0.0326 ± 0.0018 mSv/MBq. The critical tissues/organs receiving the highest mean sex-averaged absorbed doses were the thyroid (0.135 ± 0.079 mSv/MBq), stomach (0.069 ± 0.022 mSv/MBq), and salivary glands (parotids, 0.031 ± 0.011 mSv/MBq; submandibular, 0.061 ± 0.031 mSv/MBq). Other organs of interest were the bladder (0.102 ± 0.046 mSv/MBq) and kidneys (0.029 ± 0.009 mSv/MBq). Conclusion: Imaging using 18F-TFB imparts a radiation exposure similar in magnitude to many other 18F-labeled radiotracers. 18F-TFB shows a biodistribution similar to 99mTc-pertechnetate, a known nonorganified hNIS tracer, and is pharmacologically and radiobiologically safe in humans. Phase 2 trials for 18F-TFB as an hNIS imaging agent are warranted.

Higher body weight and distant metastasis are associated with higher radiation exposure to the household environment from patients with thyroid cancer after radioactive iodine therapy

There were insufficient data regarding radiation exposure to the household environment from patients with thyroid cancer who received radioactive iodine (RAI) therapy in Asia; we therefore performed the present study at the Chang Gung Memorial Hospital in Keelung, Taiwan.Patients with papillary or follicular thyroid cancer who received 3.7 GBq (100 mCi) RAI were enrolled in this prospective hospital-based study. The enrolled patients were asked to place a thermoluminescent dosimeter in the living room, bedroom, and bathroom of their houses for 4 weeks to measure radiation exposure to the household environment.A total of 43 patients (18 men and 25 women; mean age 51 ± 13 years) who received 3.7 GBq (100 mCi) RAI completed the study. The mean value of total radiation exposure over 4 weeks from the patients to the bedroom, bathroom, and living room (eliminating the background radiation factor) was 0.446 ± 0.304 (0.088-1.382) mSv. We divided the patients into 2 groups: those with more than and less than the mean value of total radiation exposure to the bedroom, bathroom, and living room. Factors associated with the higher amount of radiation exposure from the patients to the household environment were patient body weight (P = .025, univariate analysis; P = .037, multivariate analysis, odds ratio [95% confidence interval] 1.067 [1.004-1.134]) and distant metastases based on I post-therapy scanning (P = .041, univariate analysis; P = .058, multivariate analysis, odds ratio [95% confidence interval] 6.453 [0.938-44.369]); age, sex, body mass index, renal function, serum stimulated thyroglobulin level, and recombinant human thyroid-stimulating hormone use were not associated with the amount of radiation exposure from the patients to the household environment.Higher body weight and distant metastases may be the best predictors for higher radiation exposure to the household environment from patients with thyroid cancer after RAI therapy.

Hashimoto's thyroiditis predicts outcome in intrathyroidal papillary thyroid cancer

Hashimoto's thyroiditis (HT) seems to have favourable prognostic impact on papillary thyroid cancer (PTC), but data were obtained analysing all disease stages. Given that HT-related microenvironment involves solely the thyroid, we aimed to assess the relationship between HT, as detected through pathological assessment, and outcome in intrathyroidal PTC. This was a multicentre, retrospective, observational study including 301 PTC with no evidence of extrathyroidal disease. Primary study endpoint was the rate of clinical remission. Auxiliary endpoint was recurrence-free survival (RFS). HT was detected in 42.5% of the cohort and was associated to female gender, smaller tumour size, lower rate of aggressive PTC variants and less frequent post-surgery radio-iodine administration. HT showed relationship with significantly higher rate of clinical remission (P < 0.001, OR 4, 95% CI 1.78-8.94). PTCs with concomitant HT had significantly longer RFS, as compared with non-HT tumours (P = 0.004). After adjustment for other parameters affecting disease outcome at univariate analysis (age at diagnosis, histology, tumour size and multifocality), prognostic effect of HT remained significant (P = 0.006, OR 3.28, 95% CI 1.39-7.72). To verify whether HT could optimise the identification of PTCs with unfavourable outcome, we assessed the accuracy of 'non-HT status' as negative prognostic marker, demonstrating poor capability of identifying patients not maintaining clinical remission until final follow-up (probability of no clinical remission in PTCs without HT: 21.05%, 95% CI 15.20-27.93). In conclusion, our data show that HT represents an independent prognostic parameter in intrathyroidal PTC, but cannot improve prognostic specificity.

Iodine concentration calculated by dual-energy computed tomography (DECT) as a functional parameter to evaluate thyroid metabolism in patients with hyperthyroidism

BACKGROUND

Thyroid function in patients with Grave's disease is usually evaluated by thyroid scintigraphy with radioactive iodine. Recently, dual-energy computed tomography (DECT) with two different energy X-rays can calculate iodine concentrations and can be applied for iodine measurements in thyroid glands. This study aimed to assess the potential use of DECT for the functional assessment of the thyroid gland.

METHODS

Thirteen patients with Grave's disease treated at our hospital from May to September 2015 were included in this retrospective study. Before treatments, all subjects had undergone both iodine scintigraphy [three and 24 h after oral administration of 123I (20 μCi)] and non-enhanced DECT. The region of interests (ROIs) were placed in both lobes of the thyroid glands, and CT values (HU: Hounsfield unit) and iodine concentrations (mg/mL) calculated from DECT images were measured. The correlation between CT values and iodine concentrations from DECT in the thyroid gland was evaluated and then the iodine concentrations were compared with radioactive iodine uptake ratios by thyroid scintigraphy.

RESULTS

Mean (±SD) 123I uptake increased from 46.3 (±22.2) % (range, 11.1-80.1) at 3 h, to 66.5 (±15.2) % (range, 40.0-86.1) at 24 h (p < 0.01). CT values ranged from 34.5 to 98.7 HU [mean: 67.8 (±18.6)], while the iodine concentrations calculated with DECT ranged from 0.0 to 1.3 mg/mL [mean: 0.5 (±0.4)]. A moderate positive correlation between CT values and the calculated iodine concentrations in the thyroid gland was seen (R = 0.429, p < 0.05). A significant negative correlation between 123I uptake at 3 h and iodine concentration by DECT were seen (R = -0.680, p < 0.05), although no correlation was observed between 123I uptake at 3 h and CT values (p = 0.087). No correlation was observed between 123I uptake at 24 h and CT values (p = 0.153) or that between 123I uptake at 24 h and iodine concentration by DECT (p = 0.073).

CONCLUSION

The negative correlation of 123I uptake at 3 h with iodine concentration evaluated by DECT was better than that observed with simple CT value. DECT may have a potential role in the evaluation of iodine turnover in hyperthyroid patients.

Differentiated Thyroid Cancer-Treatment: State of the Art

Differentiated thyroid cancer (DTC) is a rare malignant disease, although its incidence has increased over the last few decades. It derives from follicular thyroid cells. Generally speaking, the prognosis is excellent. If treatment according to the current guidelines is given, cases of recurrence or persistence are rare. DTC requires special expertise by the treating physician. In recent years, new therapeutic options for these patients have become available. For this article we performed a systematic literature review with special focus on the guidelines of the American Thyroid Association, the European Association of Nuclear Medicine, and the German Society of Nuclear Medicine. For DTC, surgery and radioiodine therapy followed by levothyroxine substitution remain the established therapeutic procedures. Even metastasized tumors can be cured this way. However, in rare cases of radioiodine-refractory tumors, additional options are to be discussed. These include strict suppression of thyroid-stimulating hormone (also known as thyrotropin, TSH) and external local radiotherapy. Systemic cytostatic chemotherapy does not play a significant role. Recently, multikinase or tyrosine kinase inhibitors have been approved for the treatment of radioiodine-refractory DTC. Although a benefit for overall survival has not been shown yet, these new drugs can slow down tumor progression. However, they are frequently associated with severe side effects and should be reserved for patients with threatening symptoms only.

Alternative Means of Estimating 131I Maximum Permissible Activity to Treat Thyroid Cancer

To protect bone marrow from overirradiation, the maximum permissible activity (MPA) of ¹³¹I to treat thyroid cancer is that which limits the absorbed dose to blood (as a surrogate of marrow) to less than 200 cGy. The conventional approach (method 1) requires repeated γ-camera whole-body measurements along with blood samples. We sought to determine whether reliable MPA values can be obtained by simplified procedures. Methods: Data acquired over multiple time points were examined retrospectively for 65 thyroid cancer patients, referred to determine ¹³¹I uptake and MPA for initial treatment after thyroidectomy (n = 39), including 17 patients with compromised renal function and 22 patients with known (n = 16) or suspected (n = 6) metastases. The total absorbed dose to blood (D_Total) was the sum of mean whole-body γ-ray dose component (D_γ) from uncollimated γ-camera measurements and dose due to β emissions (D_β) from blood samples. Method 2 estimated D_Total from D_β alone, method 3 estimated D_Total from D_γ alone, and method 4 estimated D_Total from a single 48-h γ-camera measurement. MPA was computed as 200 cGy/D_Total for each D_Total estimate. Results: Method 2 had the strongest correlation with conventional method 1 (r = 0.98) and values similar to method 1 (21.0 ± 13.7 cGy/GBq vs. 21.0 ± 14.1 cGy/GBq, P = 0.11), whereas method 3 had a weaker (P = 0.001) correlation (r = 0.94) and method 4 had the weakest (P < 0.0001) correlation (r = 0.69) and lower dose (16.3 ± 14.8 cGy/GBq, P < 0.0001). Consequently, correlation with method 1 MPA was strongest for method 2 MPA (r = 0.99) and weakest for method 4 (r = 0. 75). Method 2 and method 1 values agreed equally well regardless of whether patients had been treated with ¹³¹I previously or had abnormal renal function. Conclusion: Because MPA based on blood measurements alone is comparable to MPA obtained with combined body counting and blood sampling, blood measurements alone are sufficient for determining MPA.

Novel Application of Quantitative Single-Photon Emission Computed Tomography/Computed Tomography to Predict Early Response to Methimazole in Graves' Disease

Objective

Since Graves' disease (GD) is resistant to antithyroid drugs (ATDs), an accurate quantitative thyroid function measurement is required for the prediction of early responses to ATD. Quantitative parameters derived from the novel technology, single-photon emission computed tomography/computed tomography (SPECT/CT), were investigated for the prediction of achievement of euthyroidism after methimazole (MMI) treatment in GD.

Materials and Methods

A total of 36 GD patients (10 males, 26 females; mean age, 45.3 ± 13.8 years) were enrolled for this study, from April 2015 to January 2016. They underwent quantitative thyroid SPECT/CT 20 minutes post-injection of ^99mTc-pertechnetate (5 mCi). Association between the time to biochemical euthyroidism after MMI treatment and %uptake, standardized uptake value (SUV), functional thyroid mass (SUVmean × thyroid volume) from the SPECT/CT, and clinical/biochemical variables, were investigated.

Results

GD patients had a significantly greater %uptake (6.9 ± 6.4%) than historical control euthyroid patients (n = 20, 0.8 ± 0.5%, p < 0.001) from the same quantitative SPECT/CT protocol. Euthyroidism was achieved in 14 patients at 156 ± 62 days post-MMI treatment, but 22 patients had still not achieved euthyroidism by the last follow-up time-point (208 ± 80 days). In the univariate Cox regression analysis, the initial MMI dose (p = 0.014), %uptake (p = 0.015), and functional thyroid mass (p = 0.016) were significant predictors of euthyroidism in response to MMI treatment. However, only %uptake remained significant in a multivariate Cox regression analysis (p = 0.034). A %uptake cutoff of 5.0% dichotomized the faster responding versus the slower responding GD patients (p = 0.006).

Conclusion

A novel parameter of thyroid %uptake from quantitative SPECT/CT is a predictive indicator of an early response to MMI in GD patients.

Gaussian plume atmospheric modelling and radiation exposure calculations following the cremation of a deceased thyroid cancer patient treated with iodine-131

Shortly after treatment with 7200 MBq of ¹³¹I, a thyroid cancer patient died and was subsequently cremated. Calculations of the atmospheric emissions of ¹³¹I from the crematorium flue were performed using a standard atmospheric pollution Gaussian Plume Dispersal model. Estimates of whole-body and thyroid dose of those potentially exposed were made using OLINDA/EXM dosimetry software. Under the meteorological conditions prevalent at the time of the cremation, and depending on the actual release rate of the ¹³¹I, the Western Australian legal limit of 3.7 Bqm^-3 for atmospheric emissions of ¹³¹I may have been exceeded for distances of up to 440 and 1610 m downwind of the crematorium chimney, with the maximum concentration being between 33 and 392 Bqm^-3. Assuming 16% of the inhaled ¹³¹I was taken up in the thyroid with the balance in the remainder of the body, the radiation dose to maximally exposed individuals was calculated to be approximately 17.7 μSv to the thyroid and 0.04 μSv to the whole-body. Despite the maximum allowable atmospheric ¹³¹I concentration of 3.7 Bqm^-3 being exceeded, as the number of people immediately downwind of the crematorium flue in the high concentration zones was very low, and considering the relatively high tolerable dose to the thyroid, the radiation dose to people was probably not a problem in this case. The local limit of 1000 MBq of ¹³¹I for the cremation of a deceased patient is reasonable, but with adequate precautions could be significantly increased without any harmful effects to people or the environment.

Higher preablative serum thyroid-stimulating hormone level predicts radioiodine ablation effectiveness in patients with differentiated thyroid carcinoma

INTRODUCTION

Radioiodine ablation of remnant thyroid tissue is an important adjuvant therapy of differentiated thyroid carcinoma (DTC) after thyroidectomy. Elevated serum thyroid-stimulating hormone (TSH) level is necessary for successful ablation. The optimum level of serum TSH level necessary for successful radioiodine ablation of well-DTC is, however, yet to be defined. We aimed to determine whether higher serum TSH level will result in a better rate of complete ablation of well-DTC using iodine-131 (I) following initial thyroidectomy.

PATIENTS AND METHODS

A total of 109 patients with differentiated thyroid cancer were divided into four treatment groups on the basis of serum TSH levels. They were followed up from 6 to 12 months after treatment with stimulated serum thyroglobulin level and a diagnostic whole-body scan with radioactive iodine I to determine early response.

RESULTS

Sixty-four patients had papillary thyroid carcinoma, whereas 45 patients had follicular carcinoma. An excellent response was observed in 66.7% of patients with TSH level more than 90 μIU/ml, 72.2% in the group with TSH level of 60-89 μIU/ml, 48.5% when TSH was 30-59 μIU/ml and 26.7% when TSH was less than 30 μIU/ml (P=0.002).

CONCLUSION

Higher preablative serum TSH predicts a better rate of ablation in patients with differentiated thyroid cancer treated with I after thyroidectomy.

Technical Note: Determination of individual thyroid clearance effective half-life with a common handheld electronic dosimeter

PURPOSE

To determine the thyroid clearance effective half-life T with a common handheld electronic dosimeter (ED) in patients undergoing radioiodine treatment for hyperthyroidism.

METHODS

Dose rates from 12 inpatients were measured daily with an ED and with a clinical uptake counter. The ED was attached to the patient with two different setups, one using a cervical collar and another employing a neck strap. Estimation of T was performed by linear regression analysis of the log of both the ED and the uptake counter measurements versus time. The latter provided the reference data.

RESULTS

Based on repeated neck strap dose rate measurements, individual Ts were determined with clinically required accuracy. The mean difference from the reference method equaled to -0.09 ± 0.35 days.

CONCLUSIONS

Determination of individual T is feasible with a common handheld ED using the simple and easy to instruct neck strap measurement setup. This simple method complements stationary uptake counter measurements and thus may improve the accuracy of radioiodine treatment planning by adding an individual T for dose calculation.

Radioactive Iodine Therapy of Differentiated Thyroid Carcinoma: Redesigning the Paradigm

Radioactive iodine therapy has evolved over the past 70 years from treatment of known metastatic thyroid carcinoma to include adjuvant use to decrease the incidence of recurrent disease and to ablation of normal remnant tissue following thyroidectomy, even for minimal tumor involvement. Advances in laboratory testing, development of drugs useful in radioiodine treatment, as well as advances in radiation detection and imaging instrumentation, have progressively improved the utility of radioiodine therapy of differentiated thyroid carcinoma. Guidelines have proliferated and they have become more detailed and complex. This trend is likely to continue as the science and technology involved increases in sophistication and efficacy.

[Radioiodine therapy for benign thyroid diseases (version 5). German Guideline]

The version 5 of the guideline for radioiodine therapy of benign thyroid disorders is an update of the version 4, which was published by the German Society of Nuclear Medicine (Deutsche Gesellschaft für Nuklearmedizin, DGN) in co-ordination with the German Society of Endocrinology (Deutsche Gesellschaft für Endokrinologie, DGE, Sektion Schilddrüse) and the German Society of General- and Visceral-Surgery (Deutsche Gesellschaft für Allgemein- und Viszeralchirurgie, DGAV) in 2007. This guideline was harmonized with the recommendations of the European Association of Nuclear Medicine (EANM). According to the German "Directive on Radiation Protection in Medicine" the physician specialised in nuclear medicine ("Fachkunde in der Therapie mit offenen radioaktiven Stoffen") is responsible for the justfication to treat with radioiodine. Therefore, relevant medical indications for radioiodine therapy and alternative therapeutic options are discussed within the guideline. This procedure guideline is developed in the consensus of a representative expert group. This fulfils the level S1 (first step) within the German classification of Clinical Practice Guidelines.

Adverse Reactions to Radioiodine 131I Therapy of Goiter in West African Tertiary Hospital

OBJECTIVE

Radioactive iodine therapy (RAIT) is established as an efficient means of treating toxic goiter (TG) globally. The field of nuclear medicine (NM) still appears novel to many Nigerian clinicians and patients. A culturally embedded dread of radiation may raise ethical and moral concerns about potential adverse effects in the wake of RAIT in our setting. An adverse drug reaction may be described as "a response to a drug which is noxious and unintended, and which occurs at doses normally used in man". This study therefore, seeks to review adverse reactions (ARs) experienced following RAIT. We would also like to improve patient and physician education about the safety profile of RAIT.

METHODS

This is a retrospective analysis of all patients who had received RAIT for thyroid disease from August 2006 to June 2015.

RESULTS

Forty typical ARs were experienced following 36 therapy sessions (18.65%) with RAIT in 35 patients (21.47%) aged 17-78 years, of which three had multiple sessions for well-differentiated thyroid carcinoma (WDTC).

CONCLUSION

RAIT remains a safe option for the treatment of benign and TG. The experienced ARs are mainly mild to moderate in severity and mostly short-lived. As larger doses of radioactive iodine for WDTC and TG were more commonly associated with ARs, our study suggests that these patients merit stronger prophylactic measures as well as closer monitoring for earlier detection and management of these reactions.

Whole-remnant and maximum-voxel SPECT/CT dosimetry in 131 I-NaI treatments of differentiated thyroid cancer

PURPOSE

To investigate the possible differences between SPECT/CT based whole-remnant and maximum-voxel dosimetry in patients receiving radio-iodine ablation treatment of differentiated thyroid cancer (DTC).

METHODS

Eighteen DTC patients were administered 1.11 GBq of 131 I-NaI after near-total thyroidectomy and rhTSH stimulation. Two patients had two remnants, so in total dosimetry was performed for 20 sites. Three SPECT/CT scans were performed for each patient at 1, 2, and 3-7 days after administration. The activity, the remnant mass, and the maximum-voxel activity were determined from these images and from a recovery-coefficient curve derived from experimental phantom measurements. The cumulated activity was estimated using trapezoidal-exponential integration. Finally, the absorbed dose was calculated using S-values for unit-density spheres in whole-remnant dosimetry and S-values for voxels in maximum-voxel dosimetry.

RESULTS

The mean absorbed dose obtained from whole-remnant dosimetry was 40 Gy (range 2-176 Gy) and from maximum-voxel dosimetry 34 Gy (range 2-145 Gy). For any given patient, the activity concentrations for each of the three time-points were approximately the same for the two methods. The effective half-lives varied (R = 0.865), mainly due to discrepancies in estimation of the longer effective half-lives. On average, absorbed doses obtained from whole-remnant dosimetry were 1.2 ± 0.2 (1 SD) higher than for maximum-voxel dosimetry, mainly due to differences in theS-values. The method-related differences were however small in comparison to the wide range of absorbed doses obtained in patients.

CONCLUSIONS

Simple and consistent procedures for SPECT/CT based whole-volume and maximum-voxel dosimetry have been described, both based on experimentally determined recovery coefficients. Generally the results from the two approaches are consistent, although there is a small, systematic difference in the absorbed dose due to differences in the S-values, and some variability due to differences in the estimated effective half-lives, especially when the effective half-life is long. Irrespective of the method used, the patient absorbed doses obtained span over two orders of magnitude.

Radioactive (131)Iodine Body Burden and Blood Dose Estimates in Treatment for Differentiated Thyroid Cancer by External Probe Counting

Radioactive¹³¹ iodine (RAI) body burden is estimated in thyroid cancer patients by a) exposure rate meter and b) external probe counting. A calibration factor of 301 cpm/MBq (d = 16 cm) is used for the probe for estimates of whole body activity. Patients sit in a rotating stool with their center corresponding to the field of view for estimation of whole body RAI. Radioactive counts are obtained for anterio posterior (AP) and postero anterior (PA) geometries. Whole body retention factor is expressed as a ratio against assayed activity administered to the patient on day 1. With exposure rate measurement, for off-thyroxin (hypothyriod) patients, the retention factors were 0.148 ± 0.12 (n = 211) and 0.07 ± 0.08 (n = 68) at 48 h and 72 h, respectively. For recombinant TSH (rhTSH) (euthyroid) group, the retention factors were 0.089 ± 0.06 (n = 24) and 0.05 ± 0.05 (n = 19) at 48 h and 72 h, respectively. By probe counting method, the obtained retention factors were 0.081 ± 0.013 (range: 0.071–0.096) (off-thyroxine group) and 0.039 ± 0.03 (range: 0.008–0.089) for the rhTSH group at 48 h. The 72 h retentions in the off thyroxine (hypothyriod) group and the rhTSH (euthyroid) group were 0.048 ± 0.024 (range: 0.016–0.076) and 0.005, respectively. The radioactive body burdens at 48 h were in the range of 290-315 MBq (7.8–8.5 mCi) for the off-thyroxine group and 44–286 MBq (1.2–7.7 mCi) for the rhTSH group. The calculated residence times in whole body were 21.97 ± 3.8 h (range: 17.1–27.1) for off-thyroxine group and 14.28 ± 2.75 h (range: 9.97-19.46) showing high statistical significance (P < 0.001). The specific blood doses were 0.118 ± 0.025 mGy/MBq (range: 0.083–0.172) for the off-thyroxine group (females n = 23); 0.87 ± 0.028 mGy/MBq (range: 0.057–0.130) (females n = 13), 0.080 ± 0.013 mGy/MBq (range: 0.069–0.098) (males n = 5) and 0.080 ± 0.028 (range: 0.059–0.118 for rhTSH patients (males n = 4). The mean mGy/MBq for blood was higher in females—about 10% for the rhTSH group compared to 40% higher for the off thyroxine (THW) group. The dose to blood was “inversely proportional” to the body weight, both in the off-thyroxine group and the rhTSH group but the dependence was not very strong with rhTSH administration because of less residence time of the radioactive iodine. There was no correlation between administered activity and retained body burden at 48 h or 72 h.

The preliminary clinical observation and analysis of childbearingage women with a history of iodine-131 treatment for Graves' disease

Whether radioactive iodine treatment of Graves' disease (GD) during pregnancy will increase pregnancy loss and affect fetal development is still a matter of concern. From May 2005 to December 2015, 2,276 childbearing-age women with GD received iodine-131 treatment in our departments and were retrospectively enrolled in our study. When some of them were found to have been pregnant, their thyroid functions were measured every 4 weeks, in addition, thyroid-stimulating hormone (TSH) was measured 6 weeks after delivery. When necessary, levothyroxine or propylthiouracil (PTU) was given in order to control their TSH levels during pregnancy. Finally, 69 pregnant women (29 ± 3.5 years old) and 1346 women who were not pregnant during the follow-up period were enrolled into this study. They were all hyperthyroid before or during pregnancy. Among 69 pregnant women, the administrated amount of iodine-131 was 254.9 ± 99.9 MBq. Fifty patients became subclinically hypothyroid after treatment and were administrated levothyroxine (55 ± 25 μg/d). Seven patients were diagnosed with subclinical hyperthyroidism during pregnancy and they received PTU (25 ± 12.5 mg/d). Twelve patients with normal thyroid function were also clinically followed. Among 69 women, 63 had a single birth, 3 had dizygotic twins, 2 had two pregnancies and 1 had a single twin birth. Sixty five babies were born full-term, while 9 were premature (4 ± 1 weeks early) with birth weight 3.2 ± 0.5 kg. Six new born babies were considered to be low birth weight infants (< 2.5 kg) while 5 were high birth weight (> 4 kg), but the weights of all the infants were within the normal range. During the period of observation to December 2015, all the infants were found to grow and develop normally. Among 1346 women who were not pregnant were in the further follow-up. Our study found no detrimental effects of the iodine-131 treatment in the pregnant women or their offspring so far.

The Influence of Antithyroid Drug Discontinuation to the Therapeutic Efficacy of (131)I in Hyperthyroidism

The influence of antithyroid drugs (ATDs) on the therapeutic efficacy of radioactive iodine in hyperthyroidism is still controversial. The aim of this study was to evaluate the effect of ATD discontinuation to the therapeutic efficacy of I-131 in hyperthyroidism patients with long-term ATD treatment. Retrospective study was done to 39 subjects with hyperthyroidism who had been treated with doses of 300 MBq radioactive iodine. The subjects were divided into three groups: Group I (n = 14) had been using ATDs for more than one year and discontinued more than three days; group II (n = 14) had been using ATDs for more than one year but discontinued only for three days or less, and group III (n = 11) has never been used any ATD before radioactive iodine treatment. There was a significant difference in the therapeutic efficacy after three months of radioactive iodine treatment between group I and group II (P = 0.018), group II and group III (P = 0.017), but not between group I and group III (P = 1.0). There was no observed difference on the therapeutic efficacy between the three groups at 6 months after radioactive iodine therapy (P = 0.143). Administration of ATDs more than 1 year without discontinuation decreased response of radioactive iodine treatment in 3 months follow-up. Discontinuation of ATDs for more than 3 days before radioactive iodine treatment is recommended.

Personalized Medicine Based on Theranostic Radioiodine Molecular Imaging for Differentiated Thyroid Cancer

Molecular imaging based personalized therapy has been a fascinating concept for individualized therapeutic strategy, which is able to attain the highest efficacy and reduce adverse effects in certain patients. Theranostics, which integrates diagnostic testing to detect molecular targets for particular therapeutic modalities, is one of the key technologies that contribute to the success of personalized medicine. Although the term "theranostics" was used after the second millennium, its basic principle was applied more than 70 years ago in the field of thyroidology with radioiodine molecular imaging. Differentiated thyroid cancer, which arises from follicular cells in the thyroid, is the most common endocrine malignancy, and theranostic radioiodine has been successfully applied to diagnose and treat differentiated thyroid cancer, the applications of which were included in the guidelines published by various thyroid or nuclear medicine societies. Through better pathophysiologic understanding of thyroid cancer and advancements in nuclear technologies, theranostic radioiodine contributes more to modern tailored personalized management by providing high therapeutic effect and by avoiding significant adverse effects in differentiated thyroid cancer. This review details the inception of theranostic radioiodine and recent radioiodine applications for differentiated thyroid cancer management as a prototype of personalized medicine based on molecular imaging.

2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer: The American Thyroid Association Guidelines Task Force on Thyroid Nodules and Differentiated Thyroid Cancer

BACKGROUND

Thyroid nodules are a common clinical problem, and differentiated thyroid cancer is becoming increasingly prevalent. Since the American Thyroid Association's (ATA's) guidelines for the management of these disorders were revised in 2009, significant scientific advances have occurred in the field. The aim of these guidelines is to inform clinicians, patients, researchers, and health policy makers on published evidence relating to the diagnosis and management of thyroid nodules and differentiated thyroid cancer.

METHODS

The specific clinical questions addressed in these guidelines were based on prior versions of the guidelines, stakeholder input, and input of task force members. Task force panel members were educated on knowledge synthesis methods, including electronic database searching, review and selection of relevant citations, and critical appraisal of selected studies. Published English language articles on adults were eligible for inclusion. The American College of Physicians Guideline Grading System was used for critical appraisal of evidence and grading strength of recommendations for therapeutic interventions. We developed a similarly formatted system to appraise the quality of such studies and resultant recommendations. The guideline panel had complete editorial independence from the ATA. Competing interests of guideline task force members were regularly updated, managed, and communicated to the ATA and task force members.

RESULTS

The revised guidelines for the management of thyroid nodules include recommendations regarding initial evaluation, clinical and ultrasound criteria for fine-needle aspiration biopsy, interpretation of fine-needle aspiration biopsy results, use of molecular markers, and management of benign thyroid nodules. Recommendations regarding the initial management of thyroid cancer include those relating to screening for thyroid cancer, staging and risk assessment, surgical management, radioiodine remnant ablation and therapy, and thyrotropin suppression therapy using levothyroxine. Recommendations related to long-term management of differentiated thyroid cancer include those related to surveillance for recurrent disease using imaging and serum thyroglobulin, thyroid hormone therapy, management of recurrent and metastatic disease, consideration for clinical trials and targeted therapy, as well as directions for future research.

CONCLUSIONS

We have developed evidence-based recommendations to inform clinical decision-making in the management of thyroid nodules and differentiated thyroid cancer. They represent, in our opinion, contemporary optimal care for patients with these disorders.

Prediction of iodine-131 biokinetics and radiation doses from therapy on the basis of tracer studies: an important question for therapy planning in nuclear medicine

OBJECTIVES

This study aimed to present a comparison of iodine-131 (I) biokinetics and radiation doses to red-marrow (rm) and whole-body (wb), following the administration of tracer and therapeutic activities, as a means of confirming whether I clearance and radiation doses for therapy procedures can be predicted by tracer activities.

METHODS

Eleven differentiated thyroid cancer patients were followed after receiving tracer and therapeutic I activity. Whole-body I clearance was estimated using radiation detectors and OLINDA/EXM software was used to calculate radiation doses to rm and wb.

RESULTS AND DISCUSSION

Tracer I activity of 86 (±14) MBq and therapeutic activity of 8.04 (±1.18) GBq were administered to patients, thereby producing an average wb I effective half-time and residence time of, respectively, 13.51 (±4.05) and 23.13 (±5.98) h for tracer activities and 13.32 (±3.38) and 19.63 (±4.77) h for therapy. Radiation doses to rm and wb were, respectively, 0.0467 (±0.0208) and 0.0589 (±0.0207) mGy/MBq in tracer studies and 0.0396 (±0.0169) and 0.0500 (±0.0163) mGy/MBq in therapy. Although the differences were not considered statistically significant between averages, those between the values of effective half-times (P=0.906), residence times (P=0.145), and radiation doses to rm (P=0.393) and to wb (P=0.272), from tracer and therapy procedures, large differences of up to 80% in wb I clearance, and up to 50% in radiation doses were observed when patients were analyzed individually, thus impacting on the total amount of I activity calculated to be safe for application in individual therapy.

CONCLUSION

I biokinetics and radiation doses to rm and wb in therapy procedures are well predicted by diagnostic activities when average values of a group of patients are compared. Nonetheless, when patients are analyzed individually, significant differences may be encountered, thus implying that nuclear medicine therapy-planning requires due consideration of changes in individual patient-body status from initial tracer to final therapy procedures to thus provide appropriate adjustments in therapeutic activities.

Methimazole discontinuation before radioiodine therapy in patients with Graves' disease

INTRODUCTION

Although radioiodine therapy (RIT) has been used for the treatment of hyperthyroidism for many decades, there is no consensus on the optimal time of methimazole (MMI) discontinuation before RIT. The aim of this clinical trial is to study the effect of three different time points of MMI discontinuation on response to RIT.

METHOD AND PATIENTS

Overall, 151 patients (18-65 years old), with Graves' disease who were taking MMI and referred to I-131 therapy, were consecutively assigned to one of three groups, and MMI was discontinued for 24-48, 48.1-72, and 72.1-168 h in group, 1, 2, and 3, respectively. Radioiodine uptake was measured in all patients and the radioiodine dose was calculated according to the Quimby formula to deliver 7.4 MBq of I-131 per gram of thyroid weight. Response to RIT was assessed at 1, 3, 6, and 12 months after RIT.

RESULTS

A total of 102 women and 49 men were included in the study. The mean administered dose of I-131 was 362.9±188.7 MBq (9.8±5.1 mCi) and the mean time to response for radioiodine was 4.1±3.6 months. There was no significant difference between the three groups in age, thyroid weight, anti-TPO level, radioactive iodine uptake level, and radioiodine dose (P>0.1). Response to RIT at 1, 3, 6, and 12 months after administration was also not different between the three groups (P>0.57).

CONCLUSION

No difference was found in the response to treatment between patients with MMI discontinuation for 24-48, 48.1-72, and 72.1-96 h before RIT. Shorter discontinuation of MMI before RIT may be preferable in most patients. Video Abstract: http://links.lww.com/NMC/A39.

131I therapy for 345 patients with refractory severe hyperthyroidism: Without antithyroid drug pretreatment

The aim of this study is to evaluate the safety and long-term results of (131)I therapy alone for patients with refractory severe hyperthyroidism without antithyroid drug pretreatment. From January 2002 to December 2012, 408 patients with refractory severe hyperthyroidism were treated with (131)I alone. Among them, 345 were followed up for 1 to 10 years for physical examination, thyroid function, and thyroid ultrasound. Complete Blood Count (CBC) liver function, electrocardiogram, echocardiogram, and Emission Computed Tomography (ECT) thyroid imaging were performed as indicated. The 345 patients had concomitant conditions including thyrotoxic heart disease, severe liver dysfunction, enlarged thyroid weighing 80 to 400 g, severe cytopenia, and vasculitis. One to two weeks prior to (131)I therapy, all patients were given low-iodine diet. The dose of (131)I therapy was 2.59 to 6.66 MBq (70 to180 µCi) per gram of thyroid with an average of 3.83 ± 0.6 MBq (103.6 ± 16.4 µCi); and the total (131)I activity administrated for the individuals was 111 to 3507.6 MBq (3.0 to 94.8 mCi, mean 444 ± 336.7 MBq (12.0 ± 9.1 mCi)). Out of the 408 patients, 283 were cured, 15 with complete remission, and 47 with incomplete remission. No treatment failure or significant clinical worsening was noted in these patients. Our data indicated that (131)I therapy alone for patients with refractory severe hyperthyroidism without antithyroid drug pretreatment is safe and effective.

A Clinical Trial of Optimal Time Interval Between Ablation and Diagnostic Activity When a Pretherapy RAI Scanning Is Performed on Patients With Differentiated Thyroid Carcinoma

This article investigates the association of the time interval between the diagnostic dose and ablation with the stunning effect, when a 74 MBq I pretherapy scanning was performed on patients with differentiated thyroid carcinoma (DTC); the patients who were diagnosed as DTC and would be performed radioiodine (RAI) ablation of thyroid remnants or metastases were recruited during January 2011 and May 2012 in our hospital.Thirty-seven patients with DTC who had the RAI ablation of thyroid remnants or metastases for the first time were recruited. All the patients received a dose of 1850 to 7400 MBq of I for ablation and a diagnostic scan was performed 24 hours after the administration of 74 MBq I before ablation. A posttherapy scan was performed 2 to 7 days after the ablation. The patients were broken down into 3 groups (G1, G2, and G3) according to the interval time between the diagnostic dose and therapy (1-3, 4-7, and >7 days). The fractional concentrations of I in remnants or functional metastases were quantified and expressed as therapeutic/diagnostic (Rx/Dx). The level of significance was set at 0.05.Sixty-seven foci were found both on pretherapy and posttherapy scans, the mean ratio of Rx/Dx was 0.43 ± 0.29, and the ratio of 49 foci (73.13%) was <0.6. The ratios in G1, G2, and G3 were 0.46 ± 0.29, 0.29 ± 0.18, and 0.55 ± 0.33, respectively. The differences between G1 and G2, and G2 and G3 were statistically significant (t = 2.40, P = 0.021 and t = 3.28, P = 0.002), whereas the difference between G1 and G3 was not significant (t = 1.01, P = 0.319).By a diagnostic scan of 74 MBq I, stunning prominently occurs with a time of 4 to 7 days between the diagnostic dose and ablation. We recommend that for less stunning effect, RAI ablation should be performed within 3 days or postponed until 1 week after the diagnostic dose administrated.

Difficulties in deciding whether to ablate patients with putatively "low-intermediate-risk" differentiated thyroid carcinoma: do guidelines mainly apply in the centres that produce them? Results of a retrospective, two-centre quality assurance study

PURPOSE

We determined the reasons for radioiodine thyroid remnant ablation, and the procedure's necessity based on postsurgical remnant size, in patients with putatively "low-intermediate-risk" differentiated thyroid carcinoma (DTC). We identified key clinicopathological, treatment and remnant characteristics, and factors associated with remnant size in 336 patients with pT1/2, M0 DTC ablated during the period September 2010 to October 2013 at one Cypriot or one Greek referral centre.

METHODS

Clinicopathological/treatment characteristics were compiled from charts. Experienced nuclear medicine physicians rated the numbers/intensities of uptake foci in the thyroid bed on postablation planar scintigrams using scales of 0-4 points and 0-3 points, respectively. The product of these scores was taken as the "remnant score" that ranged from 0 (no remnant) to 12 (multiple remnants, intense uptake).

RESULTS

DTC was predominantly papillary. The median [25th-75th percentile] longest primary tumour diameter was 1.0 cm [0.7-1.5 cm]. Despite favourable histotypes and primary tumour classifications, patients often had preablation characteristics suggesting elevated or uncertain risk: 31.0% of patients (104 of 336) had primary tumour multifocality, 22.0% (74) had confirmed cervical lymph node metastases, 37.2% (125) had unknown nodal status, and 38.1% (128) had antithyroglobulin antibody seropositivity. The median [25th-75th percentile] remnant score was 4 [2-6]; 39.9% of patients (134 of 336) had scores ≥6. For the entire cohort, T or N stages (r ≤ 0.174, P ≤ 0.05) correlated positively with the remnant score in a univariate Spearman analysis. The numbers of patients referred by the surgeon, cervical lymph nodes excised and metastatic nodes excised correlated negatively (r ≤ 0.243, P ≤ 0.038) with the remnant score, and the first two factors independently predicted the remnant score (P ≤ 0.037) in a multivariate analysis.

CONCLUSION

Patients with putatively "low-intermediate-risk" DTC frequently had disease characteristics denoting high or uncertain risk, suggesting that "selective" radioiodine ablation in such patients may seldom be applicable outside international centres of excellence. Proxies for surgeon experience and surgical completeness correlated with remnant number/uptake intensity and may aid ablation-related decision-making.

Radiation Safety Precautions in (131)I Therapy of Graves' Disease Based on Actual Biokinetic Measurements

CONTEXT

Radiation protection is an integral part of targeted radionuclide therapy. How to offer rational radiation precautions to patients with Graves' disease (GD) undergoing (131)I therapy is still a matter of ongoing discussions.

OBJECTIVE

The objective of the study was to formulate radiation precautions for GD patients undergoing (131)I therapy through actual biokinetic measurements for a particular population of patients.

DESIGN

This was a prospective study.

SETTING

The study was conducted at a university hospital.

PATIENTS

From January 2009 through January 2012, consecutive GD patients prepared for (131)I therapy were prospectively recruited.

MAIN OUTCOME MEASURES

Pretherapy thyroid radioiodine uptake and uptake ratio (4 to 24 h radioiodine uptake) were measured. Serial whole-body dose-rate measurements after therapy were performed to deduce (131)I whole-body retention. Calculations based on deduced whole-body retention and measured thyroid radioiodine biokinetics were derived to determine the thyroidal and extrathyroidal compartment uptake fractions and effective half-lives. Precaution times necessary to avoid close contact with family members and the general public were derived from these parameters and regulatory dose limits.

RESULTS

A total of 72 patients were eligible for the analysis. A high interpatient variability in (131)I biokinetics was observed: the mean peaking (131)I uptake (±1 SD) in the thyroid was 68% (±19%), and the range was 18%-89%; the mean effective (131)I half-life (±1 SD) in the remainder of the body was 5.1 (±0.9) hours (range 3.5-7.2 h). The mean measured initial dose rate (±1 SD) at 1.0 m after (131)I administration was 0.039 (±0.003) μSv·h(-1) · MBq(-1) (range 0.017-0.055 μSv·h(-1) · MBq(-1)). The 0.3:1.0 m initial dose rate ranged from 2.9 to 7.1, which was greatly lower than the projected ratio of 11.1 by the inverse square law approximation. On the basis of the measured radioiodine biokinetics and dose rates, detailed instructions were provided to limit nearby individuals' exposure.

CONCLUSION

The use of actual biokinetic measurements may remove the effect of variability errors associated with general default assumptions about the (131)I biokinetics in GD patients. The marked variability in (131)I biokinetics among GD patients reinforces the need for patient-specific iodine biokinetic measurements for radiation safety precautions.

Pediatric Graves' disease: decisions regarding therapy

PURPOSE OF REVIEW

Graves' disease is the most common cause of hyperthyroidism in the pediatric population. It occurs more often in adolescence and in girls; however, prepubertal children tend to have more severe disease, require longer medical therapy, and have a lower rate of remission as compared with pubertal children. The choice of which of the three therapeutic options to use (medical therapy, radioactive iodine ablation, or surgery) must be individualized. This update will focus on the current diagnostic and treatment modalities available, as well as address the controversy that exists with regards to permanent therapy.

RECENT FINDINGS

The diagnosis of Graves' disease is often made clinically. With the development of second-generation and third-generation thyroid-stimulating hormone receptor antibody assays, it can be more reliably confirmed. An improved understanding of the underlying autoimmune process and genetics is underway; however, remission rates in children and adolescents remain low. Because of its ease of administration and long-term follow-up, there is a trend towards permanent therapy with radioactive iodine ablation when remission cannot be achieved with medical therapy.

SUMMARY

New genes and susceptibility loci have been identified with the hope of better understanding the refractory nature of Graves' disease. Despite the low rates of remission, permanent therapy with radioactive iodine remains a good option.

Sialadenitis following low dose I-131 diagnostic thyroid scan with Thyrogen® (recombinant human thyroid stimulating hormone--thyrotropin alfa)

Salivary dysfunction and sialadenitis are well known complications of radioiodine treatment for thyroid cancer. The parotid gland is more frequently affected and the salivary gland injury is dose related. The symptoms may develop shortly after therapeutic Iodine 131(I-131) administration or months later and progress with time. The development of unilateral parotiditis following a low dose, diagnostic I-131 scan performed following Thyrogen stimulation in a patient without prior history of sialadenitis is rare in our experience, and has not been reported in the medical literature.

The nuclear medicine therapy care coordination service: a model for radiologist-driven patient-centered care

We developed a longitudinal care coordination service to proactively deliver high-quality and family-centered care in patients receiving radioiodine therapy for thyroid cancer. In an iterative, multidisciplinary team manner, a pretherapy consultation service, which included scripted interactions, documentation, and checklists for quality control, evolved over time into a robust patient-centered longitudinal care coordination nuclear medicine service. Radiation safety precautions, the rationale for therapy, and management of patient expectations were addressed through the initial consultation, and discharge and posttreatment care were managed during subsequent follow-up. The patient-physician relationship created during longitudinal nuclear medicine therapy care is one tool to help counteract the growing commoditization of radiology. This article describes the process that the nuclear medicine specialists in our department established to enhance radiologist value by providing both exceptional thyroid cancer treatment and continuity of care.

Pediatric patients with multifocal papillary thyroid cancer have higher recurrence rates than adult patients: a retrospective analysis of a large pediatric thyroid cancer cohort over 33 years

CONTEXT

Large-sample studies with long-term follow-up data are limited for pediatric patients with thyroid cancer.

OBJECTIVE

Secular changes in clinicopathological characteristics and outcomes in pediatric patients with thyroid cancer were investigated and compared with those of adults.

DESIGN AND PATIENTS

A retrospective review of 150 pediatric patients with thyroid cancer managed between 1980 and 2013 was conducted. The long-term outcomes of 124 patients followed up for 12 months or longer were evaluated. Predictors of recurrence-free survival (RFS) in pediatric patients with papillary thyroid cancer (ped-PTC group) were compared with those of 3071 adult patients.

RESULTS

The proportion of small tumors (<1 cm) increased from 9.0% before 2010 to 36.8% after 2010 (P < .001); however, neither pathological presentations such as multifocality, extrathyroidal extension (ETE), lymph node (LN) metastasis, or lung metastasis nor the RFS rate changed over time. The 5- and 10-year recurrence rates were 14.5% and 34.4% in pediatric patients, respectively. In respective analyses of the ped-PTC group and patients of all ages with papillary thyroid cancer (all ages group), the rates of ETE, LN metastasis, and lung metastasis were higher with younger age (all P for trend <.05). RFS was lower in the pediatric than the adult patients aged 20-54 years (P < .005) and was comparable with that of older patients (≥ 55 y). Only tumor multifocality and size predicted recurrence in the ped-PTC group (P < .05), whereas LN metastasis and ETE also predicted recurrence in the all-ages group (P < .01). Among patients in the all-ages group with multifocal tumors, pediatric patients had the lowest RFS (P < .05).

CONCLUSIONS

The pathological characteristics and recurrence rates of pediatric thyroid cancer have not changed over 33 years. Although younger patients present with more advanced disease, multifocality rather than age at diagnosis predicted recurrence. Recurrence was higher in pediatric than adult patients with multifocal papillary thyroid cancer.