Guidelines for radioiodine therapy of differentiated thyroid cancer

Radioactive iodine ablation post differentiated thyroid cancer surgery: an analysis of use and impact of the American Thyroid Association guidelines

BACKGROUND

The 2009 American Thyroid Association (ATA) three-tiered risk stratification, and its updated version in 2015, provided clearer guidance on the use of radioactive iodine (RAI) ablation in differentiated thyroid cancer (DTC) patients. This study examines the impact of these guidelines on RAI use in our institution.

METHODS

Patients diagnosed with DTC during three different time periods (group 1: 2002-2006, group 2: 2010-2014 and group 3: 2017-2018) were identified and risk stratified according to the ATA guidelines. RAI use and extent of surgery were compared between the three groups. Categorical variables were analysed using Fisher's exact (2 × 2) and chi-squared (>2 × 2) tests.

RESULTS

A total of 415 patients were included (group 1 = 88, group 2 = 215, group 3 = 112). The proportion of patients having total thyroidectomy were 84.6, 84.7 and 69.6% in groups 1, 2 and 3, respectively (P = 0.003). Central lymph node dissection was significantly higher in the more contemporary groups compared to group 1 (9.1 versus 41.9 versus 64.3%, P < 0.001). Overall, fewer patients received RAI in more recent times (76.6 versus 54.8 versus 26.8%, P < 0.001), most evident in the low-risk patients (70 versus 29.1 versus 5.1%, P < 0.001). In the high risk group, the majority received RAI, with no difference between the groups.

CONCLUSION

Comparing DTC patients treated in our unit before and after publications of the 2009 and 2015 ATA guidelines, more nodal surgery was performed with less RAI administered in the latter groups. Better risk stratification according to the ATA guidelines has allowed more judicious use of RAI ablation.

2019 European Thyroid Association Guidelines for the Treatment and Follow-Up of Advanced Radioiodine-Refractory Thyroid Cancer

The vast majority of thyroid cancers of follicular origin (TC) have a very favourable outcome, but 5-10% of cases will develop metastatic disease. Around 60-70% of this subset, hence less than 5% of all patients with TC, will become radioiodine refractory (RAI-R), with a significant negative impact on prognosis and a mean life expectancy of 3-5 years. Since no European expert consensus or guidance for this challenging condition is currently available, a task force of TC experts was nominated by the European Thyroid Association (ETA) to prepare this document based on the principles of clinical evidence. The task force started to work in September 2018 and after several revision rounds, prepared a list of recommendations to support the treatment and follow-up of patients with advanced TC. Criteria for advanced RAI-R TC were proposed, and the most appropriate diagnostic tools and the local, systemic and palliative treatments are described. Systemic therapy with multikinase inhibitors is fully discussed, including recommendations on how to start it and at which dosage, on the duration of treatment, and on the management of side effects. The appropriate relationship between the specialist and the patient/family as well as ethical issues are covered. Based on the available studies and on personal experience, the experts provided 39 recommendations aimed to improve the management of advanced RAI-R TCs. Above all of them is the indication to treat and follow these patients in a specialized setting which allows the interaction between several specialists in a multidisciplinary team.

Major limits of dosimetrically determined activities in advanced differentiated thyroid carcinoma

The 2013/59 EURATOM directive defines all nuclear medicine applications for therapeutic purpose as a form of radiotherapy and underlines the need of both justification and optimization of these procedures, including radioactive iodine therapy (RAIT) with [131I] for metastatic differentiated thyroid cancer (DTC). In metastatic DTC, optimal activity to be administered to achieve the best response rate with limited toxicity is still a matter of debate and international guidelines do not provide univocal recommendations on the preferable use of empiric versus a dosimetry-based approach in these patients. The purpose of this literature review is to describe the possible limits of dosimetry in RAIT planning according to methodological aspects, tumoral heterogeneity and to report clinical data on the impact on patients' outcome of different approaches. Due to the lack of standardized dosimetry protocols and clinical data assessing the superiority of a dosimetry-based vs an empiric approach in these patients, there is a need of standardisation and prospective, properly conducted studies to validate and to assess the best approach.

ICRP Publication 140: Radiological Protection in Therapy with Radiopharmaceuticals

Radiopharmaceuticals are increasingly used for the treatment of various cancers with novel radionuclides, compounds, tracer molecules, and administration techniques. The goal of radiation therapy, including therapy with radiopharmaceuticals, is to optimise the relationship between tumour control probability and potential complications in normal organs and tissues. Essential to this optimisation is the ability to quantify the radiation doses delivered to both tumours and normal tissues. This publication provides an overview of therapeutic procedures and a framework for calculating radiation doses for various treatment approaches. In radiopharmaceutical therapy, the absorbed dose to an organ or tissue is governed by radiopharmaceutical uptake, retention in and clearance from the various organs and tissues of the body, together with radionuclide physical half-life. Biokinetic parameters are determined by direct measurements made using techniques that vary in complexity. For treatment planning, absorbed dose calculations are usually performed prior to therapy using a trace-labelled diagnostic administration, or retrospective dosimetry may be performed on the basis of the activity already administered following each therapeutic administration. Uncertainty analyses provide additional information about sources of bias and random variation and their magnitudes; these analyses show the reliability and quality of absorbed dose calculations. Effective dose can provide an approximate measure of lifetime risk of detriment attributable to the stochastic effects of radiation exposure, principally cancer, but effective dose does not predict future cancer incidence for an individual and does not apply to short-term deterministic effects associated with radiopharmaceutical therapy. Accident prevention in radiation therapy should be an integral part of the design of facilities, equipment, and administration procedures. Minimisation of staff exposures includes consideration of equipment design, proper shielding and handling of sources, and personal protective equipment and tools, as well as education and training to promote awareness and engagement in radiological protection. The decision to hold or release a patient after radiopharmaceutical therapy should account for potential radiation dose to members of the public and carers that may result from residual radioactivity in the patient. In these situations, specific radiological protection guidance should be provided to patients and carers.

Adequacy of Lymph Node Yield for Papillary Thyroid Cancer: An Analysis of 23,131 Patients

BACKGROUND

Threshold numbers for defining adequacy of lymph node (LN) yield have been determined for evaluation of occult nodal disease during papillary thyroid cancer (PTC) surgery. This study assesses the prevalence of adequate LN yield and estimates its association with patient clinicopathologic characteristics.

MATERIALS AND METHODS

Adult patients with cN1 pT1b or pT2 and cN0 or cN1 pT3 M0 PTC ≥1 cm who received surgery with ≥1 LN resected were identified from the National Cancer Database, 2004-2015. Adequate yield was defined as removing ≥6, 9, and 18 LNs for pT1b, pT2, and pT3 stages, respectively, based on recently published literature. Univariable and multivariable logistic regression were used to determine factors associated with adequate yield.

RESULTS

A total of 23,131 patients were included; 7544 (32.6%) had adequate LN yield. Rate of adequate yield increased from 19.9% to 36.6% over time. After adjustment, patients at academic facilities were more likely to have adequate yield than those at community centers [OR 1.94 (95% CI 1.55-2.41), P < 0.001]. Patients with more advanced tumors were less likely to have adequate yield (pT1b: 75.9% versus pT2: 64.5% versus pT3: 24.6% adequate LN yield, P < 0.001). Patients with adequate LN yield were 0.89 times likely to receive radioactive iodine compared with those with inadequate yield [OR 0.98 (95% CI 0.81-0.98), P = 0.02].

CONCLUSIONS

The rate of adequate LN yield has increased over time, but only a minority of lymphadenectomies performed for PTC can be defined as adequate. Disparities still exist based on patient and facility characteristics; patients with more advanced tumors appear less likely to have adequate LN yield.

Advantages of dosimetry in 131I therapy of differentiated thyroid carcinoma

For advanced differentiated thyroid carcinoma (DTC) several iodine-131 (131I) activity selection strategies are available. The most common approach empirical activity selection, in which the physician chooses an activity based on convention, experience and patient related parameters. The second available strategy is to perform lesion dosimetry. In this case, the activity to be administered is determined after a pretherapeutic dosimetric assessment to calculate the minimal activity required to achieve an effective absorbed dose or a maximum safe activity based on the delivered blood/bone marrow absorbed dose of 2 Gy as determined by blood and whole-body measurements. In contrast to the situation for lesion-based dosimetry, for the maximum safe activity-based approach several studies on outcome are available. In the present paper, an argument for the use of dosimetry in advanced DTC will be presented.

Cross-Talk between Inflammatory Mediators and the Epithelial Mesenchymal Transition Process in the Development of Thyroid Carcinoma

There is strong association between inflammatory processes and their main metabolic mediators, such as leptin, adiponectin secretion, and low/high-density lipoproteins, with the cancer risk and aggressive behavior of solid tumors. In this scenario, cancer cells (CCs) and cancer stem cells (CSCs) have important roles. These cellular populations, which come from differentiated cells and progenitor stem cells, have increased metabolic requirements when it comes to maintaining or expanding the tumors, and they serve as links to some inflammatory mediators. Although the molecular mechanisms that are involved in these associations remain unclear, the two following cellular pathways have been suggested: 1) the mesenchymal-epithelial transition (MET) process, which permits the differentiation of adult stem cells throughout the acquisition of cell polarity and the adhesion to epithelia, as well to new cellular lineages (CSCs); and, 2) a reverse process, termed the epithelial-mesenchymal transition (EMT), where, in pathophysiological conditions (tissue injury, inflammatory process, and oxidative stress), the differentiated cells can acquire a multipotent stem cell-like phenotype. The molecular mechanisms that regulate both EMT and MET are complex and poorly understood. Especially, in the thyroid gland, little is known regarding MET/EMT and the role of CCs or CSCs, providing an exciting, new area of knowledge to be investigated. This article reviews the progress to date in research on the role of inflammatory mediators and metabolic reprogramming during the carcinogenesis process of the thyroid gland and the EMT pathways.

Risk factors of malignant fluorodeoxyglucose-avid lymph node on preablation positron emission tomography in patients with papillary thyroid cancer undergoing radioiodine ablation therapy

F-18 fluorodeoxyglucose (FDG)-avid metastatic lesions are associated with a poor response to radioiodine ablation therapy (RIT) in papillary thyroid cancer (PTC). This study evaluated the significance of preablative FDG positron emission tomography (PET) for the assessment of risk factors and frequency of malignant FDG-avid lymph nodes in patients with PTC undergoing RIT.The study included 339 consecutive patients (mean age 46.3 ± 12.5 y; 260 females) with PTC referred for the first RIT and who underwent routine preablative FDG PET between April 2011 and February 2013. FDG-avid lymph nodes (FALNs) were identified using retrospective image reviews. The frequency of malignant FALN (mFALN), its contribution to persistent or recurrent PTC, and its risk factors were analyzed.Among the patients, 112 had FALNs (33.0%): 11 mFALNs (3.2%) and 101 benign FALNs (bFALNs, 29.8%). mFALN contributed to 55% of persistent or recurrent PTC after RIT, which was observed in 20 of 339 patients (5.9%) during the post-RIT follow-up. Among preoperative risk factors, suspicious extrathyroidal extension and lateral neck lymph node metastasis on imaging studies were associated with mFALN. Among postoperative risk factors, T3/T4 and N1b stages, higher stimulated thyroglobulin, and higher numbers of metastatic lymph nodes and dissected lymph nodes, were associated with mFALN.mFALNs were observed in a small number of patients with PTC undergoing RIT, but it contributed 55% of total recurrent or persistent disease. Increased frequency of mFALNs is associated with more advanced PTC. Preablative FDG PET has value in evaluation of patients with RIT-resistant lesions and may help determine further treatment strategies.

Recombinant Thyrotropin vs Levothyroxine Withdrawal in 131I Therapy of N1 Thyroid Cancer: A Large Matched Cohort Study (ThyrNod)

CONTEXT

Recombinant human thyrotropin (rhTSH) has been shown to be an effective stimulation method for radioactive iodine (RAI) therapy in differentiated thyroid cancer, including in those with nodal metastases (N1 DTC).

OBJECTIVES

To demonstrate the noninferiority of rhTSH vs thyroid hormone withdrawal (THW) in preparation to RAI regarding disease status at the first evaluation in the real-life setting in patients with N1 DTC.

DESIGN

This was a French multicenter retrospective study. Groups were matched according to age (<45/≥45 years), number of N1 nodes (≤5/>5 lymph nodes), and stage (pT1-T2/pT3).

RESULTS

The cohort consisted of 404 patients pT1-T3/N1/M0 DTC treated with rhTSH (n = 205) or THW (n = 199). Pathological characteristics and initially administrated RAI activities (3.27 ± 1.00 GBq) were similar between the two groups. At first evaluation (6 to 18 months post-RAI), disease-free status was defined by thyroglobulin levels below threshold and a normal ultrasound. Disease-free rate was not inferior in the rhTSH group (75.1%) compared with the THW group (71.9%). The observed difference between the success rates was 3.3% (-6.6 to 13.0); rhTSH was therefore considered noninferior to THW because the upper limit of this interval was <15%. At the last evaluation (29.7 ± 20.7 months for rhTSH; 36.7 ± 23.8 months for THW), 83.5% (rhTSH) and 81.5% (THW) of patients achieved a complete response. This result was not influenced by any of the known prognostic factors.

CONCLUSIONS

A preparation for initial RAI treatment with rhTSH was noninferior to that with THW in our series of pT1-T3/N1/M0-DTC on disease-free status outcomes at the first evaluation and after 3 years.

Biokinetics and dose assessment after iodine intake in a thyroidectomised rat model

Procedures using iodine-131 represent more than 90% of all therapies in nuclear medicine in Algeria. It is important to evaluate the long-term biological effects of iodine treatment on non-target organs to improve patient radiation protection. This experimental radiotoxicology study aims to determine the biokinetic models of iodine contamination. For this purpose, two Wistar rat models, with and without a thyroid, have been used to evaluate the biological half-life of iodine and then to perform a biodistribution study of iodine activity in 15 organs and tissues. For the most relevant organs, the respective absorbed doses have been calculated using RODES software.

99mTc-Pertechnetate Scintigraphy Predicts Successful Postoperative Ablation in Differentiated Thyroid Carcinoma Patients Treated with Low Radioiodine Activities

BACKGROUND

Postoperative routine radioiodine (RAI) treatment is currently debated for patients with low-risk differentiated thyroid carcinoma (DTC) patients. If performed, a low ¹³¹I activity (i.e., 1 to 2 GBq) is recommended with the aim to ablate thyroid remnant and facilitate subsequent follow-up by thyroglobulin measurement. The purpose of this study was to evaluate the relationship between postsurgical technetium-99m (^99mTc)-pertechnetate scintigraphy and the rate of successful remnant ablation after low activity radioiodine ablation in patients with DTC.

METHODS

Enrolled were 193 patients with low risk DTC who underwent total thyroidectomy and RAI ablation with a fixed 1.1 GBq activity of ¹³¹I. ^99mTc-pertechnetate scans were done and thyrotropin stimulated thyroglobulin (sTg) levels measured just before ablation. Ablation effectiveness was assessed 6 to 12 months later by sTg measurement, neck ultrasound and diagnostic whole body scan.

RESULTS

A negative ^99mTc-perthecnetate scans was the best predictor of successful ablation (P<0.001) followed by preablative sTg levels <0.8 ng/mL (P=0.008) and ^99mTc-pertechnetate uptake rate values <0.9% (P=0.065). Neither sex nor age of the patient at the time of ablation or tumor histology and size showed a significant association with the rate of successful ablation.

CONCLUSION

The ^99mTc-pertechnetate scintigraphy is a simple and feasible tool to predict effectiveness of low activity ¹³¹I thyroid to ablate thyroid remnants in patients with DTC.

PET/CT in thyroid nodule and differentiated thyroid cancer patients. The evidence-based state of the art

A more conservative approach to the clinical management of thyroid nodules and differentiated thyroid cancer has recently been proposed by the 2015 ATA guidelines. In this context, fine-needle aspiration biopsy has been reserved for nodules with particular ultrasound features or dimensions that exclude low-risk thyroid lesions. Accordingly, a less aggressive surgical approach (i.e. lobectomy) has been recommended as the first-choice treatment in nodules with indeterminate cytology or in small cytologically confirmed malignant nodules. At the same time, radioactive remnant ablation has been considered only for DTC patients with concrete risks of disease persistence/relapse after thyroidectomy. In addition, further radioactive iodine therapies (RAI) have been proposed only for patients presenting unresectable and iodine-avid structural relapse. In this complex scenario, which requires attention to each clinical aspect of the patient, the introduction of accurate diagnostic tools is highly warranted. PET/CT is a very sensitive and specific diagnostic procedure that can better characterize the risk of thyroid nodules, identify DTC relapse early and predict the response to RAI. Thus, it seems essential to customize a more conservative approach to thyroid nodules and DTC patients. The aim of this review is to report the principal clinical context in which PET/CT has been used and to evaluate the evidence-based support for each diagnostic indication.

Determination of effective half-life of 131I in patients with differentiated thyroid carcinoma: comparison of cystatin C and creatinine-based estimation of renal function

PURPOSE

Renal function and effective half-life (t_1/2,eff) of I-131 have not been fully elucidated in patients undergoing radioiodine therapy (RAIT) for differentiated thyroid cancer (DTC). Aim of the present analysis was to evaluate the potential of cystatin C-based estimated glomerular filtration rate (eGFR_CysC) in comparison to conventional creatinine (eGFR_Crea) and to verify which methods to determine t_1/2,eff are most accurate to predict t_1/2,eff.

METHODS

Forty-eight patients receiving whole-body I-131-scintigraphy were included. eGFR_CysC was compared to eGFR_Crea with regard to accuracy of t_1/2,eff prediction. Three different methods (i.e. blood-based, gamma camera-based and probe-based) and two protocols with either three (short period,SP; up to 42 h) or four (long period,LP; up to 114 h) time points were compared using the Akaike's information criterion.

RESULTS

The eGFR_CysC measurement is more likely than eGFR_Crea in predicting the t_1/2,eff. High correlation coefficients were found between t_1/2,eff assessed by gamma camera and probe measurements and blood-based determination revealed lower values. Patients with normal eGFR showed higher values of t_1/2,eff of LP compared to SP.

CONCLUSIONS

eGFR_CysC should be included in further study protocols. As camera and probe measurements lead to almost superimposable results, one of the methods is expendable. Blood-based results of t_1/2,eff were lower, presumably due to unspecific iodine retention, whereas the lower correlation with renal function may be caused by individual differences in intestinal iodine resorption. SP-protocols up to 42 h after I-131 administration are sufficient to determine t_1/2,eff. Further studies are necessary for specific recommendations regarding I-131 activity reduction during RAIT in patients with DTC and renal insufficiency.

Radioiodine treatment of differentiated thyroid cancer related to guidelines and scientific literature

In differentiated thyroid cancer (DTC), radioiodine is administered to eliminate residual normal thyroid tissue after thyroidectomy (ablative treatment), to treat residual microscopic disease (adjuvant treatment), and to treat macroscopic or metastatic disease. Currently, treatment of DTC with ¹³¹I is still a matter of controversy due to the absence of prospective clinical trials assessing its benefit in terms of overall survival and recurrence-free interval. The current recommendations of the experts are based on observational retrospective data and on their interpretation of the literature. Pending the results of the prospective trials that are currently underway, the use of ¹³¹I seems to be justified not only in high-risk patients, but also in intermediate-risk and low-risk patients. The guidelines of The American and British Thyroid Association, European and American Societies of Nuclear Medicine, The European Consensus Group and the latest edition of National Comprehensive Cancer Network (NCCN) were considered in drawing up this continuing education document, we also undertook a review of the related scientific literature.

European Perspective on 2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer: Proceedings of an Interactive International Symposium

BACKGROUND

The American Thyroid Association (ATA) management guidelines for patients with thyroid nodules and differentiated thyroid cancer (DTC) are highly influential practice recommendations. The latest revision appeared in 2015 ("ATA 2015"). These guidelines were developed predominantly by North American experts. European experts frequently have different perspectives, given epidemiological, technological/methodological, practice organization, and medicolegal differences between the respective regions.

SUMMARY

Divergent viewpoints were the focus of an invited symposium organized by the European Association of Nuclear Medicine involving 17 European thyroidologists, four ATA Guidelines Taskforce members, and an audience of 200 international experts. The group discussed the preoperative assessment of thyroid nodules, surgery and the role of pathology, radioiodine (RAI) therapy (RAIT), the assessment of initial therapy and dynamic risk stratification, and the treatment of persistent disease, recurrences, and advanced thyroid cancer. The dialogue resulted in this position paper contrasting European and ATA 2015 perspectives on key issues. One difference pertains to the permissiveness of ATA 2015 regarding lobectomy for primary tumors ≤4 cm. European panelists cited preclusion of RAIT, potential need for completion thyroidectomy, frequent inability to avoid chronic thyroid hormone replacement, and limitations of supportive evidence as arguments against widely applying lobectomy. Significant divergence involved ATA 2015's guidance regarding RAIT. European panelists favored wider use of postoperative RAIT than does ATA 2015. Rationales included the modality's association with favorable patient outcomes and generally limited toxicity, and lack of high-quality evidence supporting withholding RAIT. Additionally, European panelists favored recombinant human thyrotropin (rhTSH) in more settings than does ATA 2015, citing avoidance of hypothyroid morbidity and quality-of-life impairment, without apparent sacrifice in oncologic outcomes. Based on clinical evidence plus theoretical advantages, European experts advocated dosimetric versus fixed-activity RAIT approaches for advanced DTC. European panelists noted that the ATA 2015 risk-stratification system requires information sometimes unavailable in everyday practice. ATA 2015 recommendations regarding RAI-refractory DTC should consider potential palliative benefits of RAIT in patients who also have RAI-susceptible lesions.

CONCLUSIONS

European panelists suggested modifications to approximately one-third of ATA 2015 recommendations. Varying European and ATA 2015 perspectives can stimulate analysis and discussion of the literature and performance of primary research to resolve discrepant recommendations and potentially improve patient outcomes.

Clinical and prognostic role of detection timing of distant metastases in patients with differentiated thyroid cancer

PURPOSE

Distant metastases (DM) from DTC occur in 5-25% of cases and are correlated to lower survival; the prognostic significance of the temporal onset of DM is unclear. Our aim was to retrospectively analyze the prevalence of DM and to assess the prognostic role of the timing of manifestation of DM regarding the outcome.

MATERIALS AND METHODS

We included 174 patients (mean age 64 years). According to the time of manifestation, DM were divided in two groups: synchronous DM (SDM, n = 108) defined as metastases present at initial diagnosis and metachronous DM (MDM, n = 66) as diagnosed during follow-up. SDM were further sub grouped in pre-RAIT when diagnosed during pre-surgery work-up (n = 35) and baseline-RAIT when detected by first whole body scan after RAIT (n = 73). Disease-specific survival (DSS) was analyzed using the Kaplan-Meier method.

RESULTS

Total RAI activities and number of treatments were significantly higher in MDM, also loss of RAI avidity was more frequent in MDM. Forty-four patients died during follow-up, of which 41 were DTC-related deaths, 5-year and 10-year DSS were 80% and 56%. On univariate analysis MDM had significantly shorter DSS; also histotype and RAI avidity were significant risk factors of impaired survival. On multivariate analysis, only loss of RAI avidity remained as independent negative predictor (p = 0.043). Considering SDM, DSS was significantly shorter in pre-RAIT group than baseline-RAIT (p = 0.004). Instead there was no significant difference between pre-RAIT-SDM and MDM in survival outcome (p = 0.875).

CONCLUSIONS

In DTC with DM, loss of RAI uptake has an important role in survival. No significant difference in survival outcome was discovered between SDM and MDM; but, among SDM, pre-RAIT had significant shorter DSS than baseline-RAIT.

Pattern of urine iodine excretion with low iodine diet during preparation for radioactive iodine ablation in patients with thyroid cancer

BACKGROUND

The optimal period of low iodine diet during preparation for radioactive iodine (RAI) ablation in an area with iodine-rich diet was investigated.

METHODS

Ninety-four patients with thyroid cancer who underwent low iodine diet and RAI were prospectively allocated into 2 groups-thyroxine withdrawal or using recombinant human thyroid stimulating hormone (rhTSH) for TSH stimulation. Their urinary iodine excretion (UIE) patterns were analyzed.

RESULTS

There was no clinicopathological difference between the 2 groups except for tumor size and lymph node status. The UIE (median iodine to creatinine ratio, I/Cr) in the withdrawal group on the 7th and 14th day were 18.3 and 17.9 μg/gCr, respectively, with adequate preparation rate of 93.3% on both days (cutoff value 100 μg/gCr). In the rhTSH group, the median I/Cr on the 7th and 14th day were 48.0 and 45.7 μg/gCr (adequate preparation rates 91.8% and 93.8%), respectively.

CONCLUSION

One week of low iodine diet is sufficient preparation for RAI regardless of method of TSH stimulation.

Radiation Safety Aspects of Iodine-131 metaiodobenzylguanidine (131I mIBG) Therapy Program Startup

As a medical center without a pre-existing radiopharmaceutical therapy program, it was a daunting endeavor to implement a I metaiodobenzylguanidine (mIBG) high-dose treatment regimen. It took several years of planning with hospital administration, vendors, and Texas Department of Health Radiological Control regulators to establish a viable program. Effective communication between physicians, nursing, nuclear medicine, environmental services, maintenance, and other support staff is essential and paramount for the successful execution and continued sustainability of the mIBG therapy program. Besides providing an effective treatment for patients, an additional goal for the program is to keep radiation exposure As Low As Reasonably Achievable (ALARA) for staff and patient caregivers. As such, start-up presented many training, logistical, and radiation safety challenges. The location of the isolation room and shielding specifications were designed to keep radiation exposure to public access areas to less than 2 microsieverts per hour. Before the first patient was treated the policies and procedures for training, radiation safety, product quality control, and infusion process needed to be developed, tested, and approved by various committees. Furthermore, a similar process was required for developing room set-up, post therapy cleanup, and waste storage procedures. Throughout the maturation process of the program, the departments involved have found that our safety culture has continually improved by the re-enforcement of knowledge and lessons learned, as both the ancillary and treatment staff grew more confident in each other's ability during more patient treatments are performed. This article describes the process and lessons learned during the time leading up to the startup and early years of the mIBG therapy program.

Impact of prompt gamma coincidence correction on absorbed dose estimation in differentiated thyroid cancer using 124I PET/CT imaging

INTRODUCTION

Iodine-124 positron emission tomography/computed tomography (I PET/CT) is increasingly being used in the absorbed dose estimation in the radioiodine treatment of differentiated thyroid cancer (DTC). However, the produced prompt gamma coincidences (PGCs) associated with the I decay result in a bias in the absorbed dose estimation. The impact of a sinogram-based PGC correction approach on the absorbed dose estimation in I PET/CT DTC imaging is investigated.

METHODS

I phantom and patient measurements were performed on a Siemens Biograph mCT PET/CT system. All images were reconstructed with (PGCon) and without PGC correction (PGCoff). The phantom contained seven spheres (diameters: 6.6-37 mm). The spheres and background compartment were filled with a I solution, resulting in a low (9.4 : 1) and a high sphere-to-background activity concentration ratio (750 : 1). Sphere recovery coefficient (RC) values were determined. In addition, the impact of PGC correction on measured lesion uptake and calculated lesion-absorbed dose was assessed for 66 lesions identified in 24 DTC patients.

RESULTS

PGC correction systematically increased sphere RC values up to 71% for the smallest spheres. For the patient data, PGC correction significantly increased both the measured I uptake (P<0.005) and the calculated lesion-absorbed dose (P=0.008) by ∼3%. The percentage difference in the calculated lesion-absorbed dose ranged from -19% to 50%, showing that PGC correction had a variable and large impact for a few lesions.

CONCLUSION

PGC correction resulted in significantly higher sphere RC values, I lesion uptake values and estimated lesion-absorbed doses.

Red bone marrow dose estimation using several internal dosimetry models for prospective dosimetry-oriented radioiodine therapy

The aim of the present study was to review the available models developed for calculating red bone marrow dose in radioiodine therapy using clinical data. The study includes 18 patients (12 females and six males) with metastatic differentiated thyroid cancer. Radioiodine tracer of 73 ± 16 MBq ¹³¹I was orally administered, followed by blood sampling (2 ml) and whole-body scans (WBSs) done at several time points (2, 6, 24, 48, 72, and ≥ 96 h). Red bone marrow dose was estimated using the OLINDA/EXM 1.0, IDAC-Dose 2.1, and EANM models, the models developed by Shen and co-workers, Keizer and co-workers and Siegel and co-workers, and Traino and co-workers, as well as the single measurement model (SMM). The results were then compared to the standard reference model Revised Sgouros Model (RSM) reported by Wessels and co-workers. The mean dose deviations of the Traino, Siegel, Shen, Keizer, OLINDA/EXM, EANM, SMM, and IDAC-Dose 2.1 models from the RSM were - 17%, - 24%, 6%, - 29%, - 15%, 40%, 48%, and - 8%, respectively. The statistical analysis demonstrated no significant difference between the results obtained with the RSM and with those obtained with the Shen, Traino, OLINDA/EXM, and IDAC-Dose 2.1 models (t test; p_value > 0.05). However, a significant difference was found between RSM doses and those obtained with the EANM, SMM, and Keizer models (t test; p_value < 0.05). The correlation between red marrow dose from the SMM and EANM models was modest (R² = 0.65), while the crossfire dose calculated with the OLINDA/EXM and IDAC-Dose 2.1 models were in good agreement with each other and with the reference model. The findings obtained indicate that most of the dosimetry models can be used for a reliable dosimetry, and the calculated total body doses can be considered as a reliable non-invasive option for a conservative activity planning. In addition, the excellent performance of the IDAC-Dose 2.1 model will be of particular importance for a practical and accurate dosimetry, with the advantages of allowing for the use of realistic advanced phantoms and updated dose fractions, and of providing information about the blood dose contribution to the red bone marrow.

Unexpected False-positive I-131 Uptake in Patients with Differentiated Thyroid Carcinoma

Objective:

Radioiodine is the most specific radionuclide for differentiated thyroid carcinoma (DTC) imaging. Despite its high specificity and sensitivity, false-positive I-131 uptake could be seen on whole body scan (WBS) that may lead to misdiagnosis and unnecessary radioiodine treatment. In this study, we aimed to present the I-131 WBS and concomitant single photon emission computed tomography/computed tomography (SPECT/CT) images of unexpected false-positive radioiodine uptake along with the patients’ clinical outcomes and the contribution of SPECT/CT imaging.

Methods:

I-131 WBSs of 1507 patients with DTC were retrospectively reviewed, and anticipated I-131 uptakes (like in breasts or thymus) were excluded from the study. The unexpected false-positive I-131 uptakes with concomitant SPECT/CT imaging were included in the study.

Results:

Twenty-one patients had 23 unexpected I-131 uptakes on WBS and concomitant SPECT/CT imaging. The vast majority (87%) of these cases were seen on post-therapeutic I-131 WBS. Most of the false-positive I-131 uptakes could be explained by SPECT/CT and radiologic findings, and were secondary to non-thyroid conditions (bronchiectasis, lung infection, subcutaneous injection into gluteal fatty tissue, aortic calcification, benign bone cyst, vertebral hemangioma, recent non-thyroid surgical procedure site, rotator cuff injury, mature cystic teratoma and ovarian follicle cyst). However, the possible reasons of 9 false-positive I-131 uptakes could not be explained by radiologic findings.

Conclusion:

We suggest that false-positive I-131 uptake and its underlying mechanisms (inflammation, trapping, increased perfusion, etc.) must be kept in mind in patients with thyroid cancer and unexpected findings must be considered together with serum thyroglobulin levels, SPECT/CT and radiologic findings in order to avoid misdiagnosis and unnecessary radioiodine treatment.

Possible delayed diagnosis and treatment of metastatic differentiated thyroid cancer by adopting the 2015 ATA guidelines

OBJECTIVE

According to the 2015 American Thyroid Association (ATA) guidelines, thyroid ablation by iodine-131 (I-131) therapy is absolutely recommended only in patients with high-risk differentiated thyroid cancer (DTC). Often distant metastases are not recognized early and they can stay silent for long time. The aim of our study was to retrospectively analyze the prevalence of metastatic disease before and after I-131 and to evaluate the influence of the new ATA guidelines in the management of DTC.

METHODS

We retrospectively analyzed 140 patients showing distant metastases. All metastases were detected by whole-body scan after I-131 and confirmed by histology and/or other imaging modalities.

RESULTS

In 26/140 patients metastases were detected before I-131, while in 114/140 were discovered after I-131. Comparing patients with metastases detected before and after I-131, no differences were demonstrated considering age, sex, histotype, tumor size, multifocality of cancer and metastatic localization. Metastatic DTC discovered before radioiodine had higher thyroglobulin and received a higher radioiodine total activity and number of treatments. Considering patients with distant metastases, according to the 2015 ATA guidelines, 38 patients would have been categorized as high risk, 22 as low risk and 80 as intermediate risk. Among intermediate-risk patients, only in 25 cases (31%) I-131 treatment would have been appropriate according to 2015 ATA recommendations; in the remaining 56 cases (69%), I-131 would not have been recommended.

CONCLUSIONS

According to the 2015 ATA guidelines, most of metastatic patients would not have been treated after surgery, with the risk of late diagnosis and delayed treatment.

Thyroid Cancer Radiotheragnostics: the case for activity adjusted 131I therapy

Radiotheragnostics represents the systematic integration of diagnostic imaging and therapeutics using radionuclides targeting specific characteristics of tumor biology. Radioiodine (¹³¹I) is the classic radiotheragnostic agent used for the diagnosis and treatment of differentiated thyroid cancer (DTC) based on sodium-iodine symporter expression in normal and neoplastic thyroid tissue. Application of radiotheragnostics principles in thyroid cancer involves using pre-ablation diagnostic scans (Dx Scans) for detection of iodine-avid regional and distant metastatic disease and patient-individualized targeted ¹³¹I therapy with goal of maximizing the benefits of the first therapeutic ¹³¹I administration. Clinically available nuclear medicine imaging technology has significantly evolved over the past 10 years with the introduction of hybrid SPECT/CT and PET/CT systems, as well as advances in iterative image reconstruction with modeling of image degrading physical factors. This progress makes possible the acquisition of accurate diagnostic radioiodine scintigraphy capable of identifying regional and distant metastatic disease, which can be used for ¹³¹I treatment planning and delivery of activity adjusted ¹³¹I therapy for achieving intended treatment goals (e.g. remnant ablation, adjuvant ¹³¹ I treatment and targeted 131-I treatment). The overarching aim of thyroid cancer radiotheragnostics is to optimize the balance between ¹³¹I therapeutic efficacy and potential side-effects on non-target tissues.

Low-Dose Radioiodine Ablation in Patients with Low-Risk Differentiated Thyroid Cancer

AIM

Based on the response criteria of the 2015 American Thyroid Associations guidelines, our objectives were to -determine the response rate when using a low dose of -131-I GBq in patients with low-risk differentiated thyroid cancer (LRDTC) and the influence of clinical and analytical variables on the prediction of complete response.

METHODS

We performed a multicentre and longitudinal study, including patients who were operated for LRDTC and who underwent radioiodine remnant ablation with a low-dose of 131-I. All patients were assessed at 6-12 months, and their status was classified as complete (excellent response) or incomplete response (structural incomplete, biochemical incomplete or indeterminate response). Various factors including age, gender, histology, tumour focality and size, stage, time from surgery to treatment, type of thyroid-stimulating hormone (TSH) stimulation, preablation serum thyroglobulin (pTg), antiTg antibodies (pAntiTgAb) and TSH (pTSH) levels were also analysed in order to predict the complete response rate.

RESULTS

Of 108 patients, 79.6$ achieved complete response and the remaining showed incomplete response (2.9, 5.5 and 12$ due to biochemical incomplete, structural incomplete and indeterminate response respectively). Six patients received a new dose of 131-I. Tumour size and pAntiTgAb were the only factors related to therapeutic response (p = 0.03 and p < 0.01, respectively). However, pAntiTgAb was the only independent factor related to complete -response. Patients with complete response showed lower pTg than those with incomplete response (5.1 ± 12.9 vs. 11.2 ± 25 ng/mL) although without statistical significance (p = 0.14). There was no significant difference in the response rate depending on the thyrotropin stimulation methods.

CONCLUSIONS

A low dose of 131-I was sufficient for reaching a complete response at 6-12 months of follow-up in the majority of patients with LRDTC. Tumour size and pAntiTgAb variables were related to therapeutic response.

Low versus high activity radioiodine remnant ablation for differentiated thyroid carcinoma with gross extrathyroidal extension invading only strap muscles

OBJECTIVES

The efficacy of radioiodine remnant ablation (RRA) for patients with differentiated thyroid carcinoma (DTC) with gross extrathyroidal extension (ETE) is well described in observational studies. However, its role in gross ETE invading only strap muscles, T3b category in the newly proposed eighth edition of the TNM staging system, is currently unknown.

METHODS

This study retrospectively analyzed 260 DTC patients with ETE invading only strap muscles who underwent thyroidectomy at a tertiary Korean hospital between 1994 and 2005. Cancer-specific survival (CSS) and recurrence-free survival (RFS) in the no RRA (n = 13), low RRA activity (<3.7 GBq, n = 80), and high RRA activity (≥3.7 GBq, n = 167) groups were studied.

RESULTS

No significant differences were observed between low and high activity RRA groups in terms of 10-year CSS (97.3% versus 99.3%; HR 0.23, 95% CI 0.02-2.57; p = .235) and RFS (86.8% versus 88.8%; 0.90, 0.40-2.03; p = .804). In the no RRA group, no patients died of cancer, and only one developed structural recurrence. In Cox regression analyses with inverse probability of treatment weighting adjusted for clinicopathologic risk factors, high activity RRA was not related to recurrence outcomes compared to low activity (HR 0.60, 95% CI 0.26-1.35; p = .214).

CONCLUSIONS

Long term oncologic outcomes did not significantly differ between low versus high activity RRA groups, which suggests that low activity RRA might be sufficient in patients with DTC with gross ETE invading only strap muscles. Further studies are needed to clarify the optimal activity of RRA in these patients.

[18F]Tetrafluoroborate ([18F]TFB) and its analogs for PET imaging of the sodium/iodide symporter

Sodium/iodide symporter (NIS)-mediated iodide uptake in thyroid follicular cells is the basis of clinical utilization of radioiodines. The cloning of the NIS gene enabled applications of NIS as a reporter gene in both preclinical and translational research. Non-invasive NIS imaging with radioactive iodides and iodide analogs has gained much interest in recent years for evaluation of thyroid cancer and NIS reporter expression. Although radioiodines and [^99mTc]pertechnetate ([^99mTc]TcO₄^-) have been utilized in positron emission tomography (PET) and single photon emission computed tomography (SPECT), they may suffer from limitations of availability, undesirable decay properties or imaging sensitivity (SPECT versus PET). Recently, [¹⁸F]tetrafluoroborate ([¹⁸F]TFB or [¹⁸F]BF₄^-) and other fluorine-18 labeled iodide analogs have emerged as a promising iodide analog for PET imaging. These fluorine-18 labeled probes have practical radiosyntheses and biochemical properties that allow them to closely mimic iodide transport by NIS in thyroid, as well as in other NIS-expressing tissues. Unlike radioiodides, they do not undergo organification in thyroid cells, which results in an advantage of relatively lower uptake in normal thyroid tissue. Initial clinical trials of [¹⁸F]TFB have been completed in healthy human subjects and thyroid cancer patients. The excellent imaging properties of [¹⁸F]TFB for evaluation of NIS-expressing tissues indicate its bright future in PET NIS imaging. This review focuses on the recent evolution of [¹⁸F]TFB and other iodide analogs and their potential value in research and clinical practice.

The role of radioactive iodine therapy in papillary thyroid cancer: an observational study based on SEER

BACKGROUND

Papillary thyroid cancer (PTC) is a common endocrine malignancy with relatively good prognosis. Radioactive iodine (RAI) is considered effective for patients with total or nearly total thyroidectomy, but the beneficial effects of RAI are still controversial.

MATERIALS AND METHODS

To determine whether RAI therapy could improve the survival rates of PTC patients, we conducted a retrospective analysis using data from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program. Disease-specific survival (DSS) was obtained using multivariate Cox proportional hazard regressions.

RESULTS

DSS was improved by RAI ablation in patients with tumor >2 cm, age >45 years and gross extrathyroidal or lymph node metastasis. In a further analysis, RAI therapy did not improve the DSS in patients with tumor <2 cm except those with distant metastasis. For patients with tumor >2 cm, those involving gross extrathyroidal extension, age >45 years or disease in the lymph nodes, DSS was improved after RAI therapy. Patients with distant metastasis always benefited from RAI ablation.

CONCLUSION

RAI ablation should be recommended to patients with tumor <2 cm and distant metastasis or patients with tumor >2 cm and one of the following risk factors: gross extrathyroidal extension, age >45 years, lymph node and distant metastases.

Radioprotective effect of vitamin E on salivary glands after radioiodine therapy for differentiated thyroid cancer: a randomized-controlled trial

OBJECTIVES

This study aimed to examine the radioprotective effect of vitamin E on salivary glands after radioactive iodine (I) therapy in patients with differentiated thyroid cancer.

PATIENTS AND METHODS

Eighty-two patients with differentiated thyroid cancer were enrolled in this study. They were divided randomly into four groups (control group: 22 cases, group A: 23 cases, group B: 22 cases, and group C: 15 cases) before postsurgical ablation therapy with 100 mCi I. The patients in groups A, B, and C received vitamin E 100, 200, and 300 mg/day orally, respectively, for a duration of 1 week before to 4 weeks after I therapy. Salivary gland function was assessed using salivary gland scintigraphy immediately before and 6 months after I therapy. Uptake fraction (UF), uptake index (UI), excretion fraction (EF), and excretion ratio (ER) of each salivary gland were measured and compared.

RESULTS

On comparison between before and after I therapy in the control group, there was a significant decrease in UF of both right and left parotid glands (all P<0.01). In group A, a significant increase in EF of the right parotid gland (P<0.01) and UI of the right submandibular gland (P<0.05) was found. In group B, there was a significant increase in UI of the right parotid gland and both submandibular glands (all P<0.01). In group C, there was a significant increase in UF of the left parotid gland (P<0.05) and the right submandibular gland (P<0.01). Also, there was a statistical increase in UI in both submandibular glands (all P<0.01). However, on comparing the changes in the post-I therapy salivary scintigraphy parameters among the four groups, there was a significant difference in ΔUI of the right parotid gland (P<0.05) and both submandibular glands (all P<0.01), as well as ΔER of the left parotid gland (P<0.05) and ΔUF of the left submandibular gland (P<0.05).

CONCLUSION

Vitamin E exerts significant protective effects on the parotid and submandibular glands after I therapy.

The effects of the Union for International Cancer Control/American Joint Committee on Cancer Tumour, Node, Metastasis system version 8 on staging of differentiated thyroid cancer: a comparison to version 7

OBJECTIVE

To assess the changes resulting from the changes from UICC/AJCC TNM version 7 to version 8 and to subsequently determine whether TNM version 8 is an improvement compared to previous iterations of the TNM system and other staging systems for differentiated thyroid cancer (DTC) with regard to prognostic power.

DESIGN

Database study of DTC patients treated in our centre between 1978 up to and including 1 July 2014. Results were compared to our previous comparison of prognostic systems using the same data set.

PATIENTS

2257 DTC patients.

MEASUREMENTS

Staging in accordance with TNM 7 and TNM 8. Thyroid cancer-specific mortality; comparison was based on p-values of univariate Cox regression analyses as well as analysis of the proportion of variance explained (PVE).

RESULTS

There is a redistribution from stage 3 to lower stages affecting 206 (9.1%) patients. DTC-related mortality according to Kaplan-Meier for younger and older patients in TNM 7 had a slightly lower prognostic power than that in accordance with TNM 8 (P = 8.0 10^-16 and P = 1.5 10^-21 , respectively). Overall staging is lower in 627/2257 (27.8%) patients. PVE (TNM 7: 0.29; TNM 8: 0.28) and the P-value of Cox regressions (TNM 7: P = 7.1*10^-52 ; TNM 8: P = 3.9*10^-49 ) for TNM version 8 are marginally lower than that for TNM version 7, but still better than for any other DTC staging system.

CONCLUSION

TNM 8 results in a marked downstaging of patients compared to TNM 7. Although some changes, like the change in age boundary, appear to be associated with an improvement in prognostic power, the overall effect of the changes does not improve the predictive power compared to TNM 7.

Predictive factors for the outcomes of initial I-131 low-dose ablation therapy to Japanese patients with differentiated thyroid cancer

OBJECTIVE

To identify prognostic factors associated with a low-iodine diet (LID) and the amount of remnant thyroid tissue in Japanese patients with differentiated thyroid cancer (DTC) who received initial I-131 remnant ablation (RAI) using a fixed low dose of I-131 (1110 MBq).

PATIENTS AND METHODS

In this prospective study, we enrolled 45 patients. Patients were classified into a self-managed LID group and a strict LID group. We measured the urinary iodine concentration on the day of RAI after patients consumed LID for 2 weeks. Thyroid-stimulating hormone-induced thyroglobulin (Tg) levels and I-131 uptake by the remnant thyroid tissue were also evaluated. A response-evaluation whole-body scan (WBS) was performed 6-8 months after RAI to determine the outcome of the therapy.

RESULTS

Post-LID urinary iodine levels of the strict LID group tended to be lower than those of the self-managed LID group. Twenty-five cases (56%) showed absence of uptake, whereas 20 cases (44%) showed residual uptake on the response-evaluation WBS. There were no significant differences between "absence" and "residual" groups in urinary iodine concentrations and Tg levels (p = 0.253 and p = 0.234, respectively). However, significant differences were observed in I-131 uptake by the thyroid bed (p = 0.035).

CONCLUSIONS

For patients following the current Japanese method of a 2-week LID, the urinary iodine concentration was not a predictive factor for the successful outcome of RAI. In contrast, low I-131 uptake by the thyroid bed, revealed by the scintigram after RAI, may serve as a favorable predictive factor.

Robotic-assisted modified radical neck dissection using a bilateral axillo-breast approach (robotic BABA MRND) for papillary thyroid carcinoma with lateral lymph node metastasis

BACKGROUND

Although safe in patients with papillary thyroid carcinoma (PTC), robotic thyroidectomy using a bilateral axillo-breast approach (BABA) has not been frequently performed in patients with advanced PTC. This study describes surgical outcomes in patients with PTC and lymph node metastasis (LNM) in lateral neck compartment who underwent robotic-assisted modified radical neck dissection with BABA (robotic BABA MRND).

METHODS

The medical records of patients with PTC and lateral LNM who underwent robotic BABA MRND from March 2010 to July 2016 were retrospectively reviewed.

RESULTS

Fifteen patients, 14 women and 1 man, of mean age 37.1 ± 9.3 years, were enrolled. Mean operation time was 272.7 ± 33.8 min. A mean 20.7 ± 7.2 lymph nodes were retrieved from the lateral neck compartment, with a mean 5.3 ± 4.4 lymph nodes being metastatic. The rates of transient and permanent hypocalcemia were 46.7 and 0%, respectively, and the rates of transient and permanent vocal cord palsy were 6.7 and 0%, respectively. Fourteen patients (93.3%) had stimulated thyroglobulin concentrations below 2 ng/mL after the first treatment with radioactive iodine.

CONCLUSIONS

Robotic BABA MRND could be safely performed and may be a good surgical option in selected patients with PTC and lateral LNM.

Hybrid Vision-Fusion system for whole-body scintigraphy

Radioiodine therapy in the treatment of differentiated thyroid carcinoma (DTC) is used in clinical practice for the ablation of thyroid residues and/or destruction of tumour tissue. Whole-body scintigraphy for visualization of the spatial 131I distribution performed by a gamma camera (GC) is a standard procedure in DTC patients after application of radioiodine therapy. A common problem is the precise topographic localization of regions where radioiodine is accumulated even in SPECT imaging. SPECT/CT can provide precise topographic localization of regions where radioiodine is accumulated, but it is often unavailable, especially in developing countries because of the high price of the equipment. In this paper, we present a Vision-Fusion system as an affordable solution for 1) acquiring an optical whole-body image during routine whole-body scintigraphy and 2) fusing gamma and optical images (also available for the auto-contour mode of GC). The estimated prediction error for image registration is 1.84 mm. The validity of fusing was tested by performing simultaneous optical and scintigraphy image acquisition of the bar phantom. The fusion result shows that the fusing process has a slight influence and is lower than the spatial resolution of GC (mean value ± standard deviation: 1.24 ± 0.22 mm). The Vision-Fusion system was used for radioiodine post-therapeutic treatment, and 17 patients were followed (11 women and 6 men, with an average age of 48.18 ± 13.27 years). Visual inspection showed no misregistration. Based on our first clinical experience, we noticed that the Vision-Fusion system could be very useful for improving the diagnostic possibility of whole-body scintigraphy after radioiodine therapy. Additionally, the proposed Vision-Fusion software can be used as an upgrade for any GC to improve localizations of thyroid/tumour tissue.

Targeted alpha-particle therapy: imaging, dosimetry, and radiation protection

Systemic or locoregionally administered alpha-particle emitters are highly potent therapeutic agents used in oncology that are fundamentally novel in their mechanism and, most likely, overcome radiation resistance as the alpha particles emitted have a short range and a high linear energy transfer. The use of alpha emitters in a clinic environment requires extra measures with respect to imaging, dosimetry, and radiation protection. This is shown for the example of ²²³Ra dichloride therapy. After intravenous injection, ²²³Ra leaves the blood and is taken up rapidly in bone and bone metastases; it is mainly excreted via the intestinal tract. ²²³Ra can be imaged in patients with a gamma camera. Dosimetry shows that, after a series of six treatments for a 70-kg person with an overall administered activity of 23 MBq, ²²³Ra results in an absorbed alpha dose of approximately 17 Gy to the bone endosteum and approximately 1.7 Gy to the red bone marrow. During administration, special care must be taken to ensure that no spill is present on the skin of either the patient or staff. Due to the low dose rate, the treatment is normally performed on an outpatient basis; the patient and carers should receive written instructions about the therapy and radiation protection.

BRAF V600E mutation in papillary thyroid cancer and its effect on postoperative radioiodine (131I) therapy: Should we modify our therapeutic strategy?

INTRODUCTION

The BRAF V600E mutation in papillary thyroid cancer (PTC) has been associated with resistance to ¹³¹I. Our aim was to quantify the response to ¹³¹I after surgery in patients who had the mutation (BRAF+) and those who did not have the mutated gene (BRAF-).

METHOD

A prospective cohort study was designed, from September 2015 to February 2016, which included patients with PTC receiving therapy after surgical treatment. Variables were described for age, gender, histology, tumor stage, thyroglobulin values before, 48h after and 6months after ¹³¹I; absorbed dose and % activity on days 2 and 7 and elimination time.

RESULTS

41 patients giving in total 67 thyroid remnants were included. 61% were BRAF+. In stagesiii and iv, 80% were BRAF+. In lateral resection, 100% were BRAF+. The number of nodes was higher in BRAF+: 3.4 vs 1.2 (P=.01). The classic variant was predominant in BRAF+ (91.7% vs 8.3%, P=.03). 85.7% vs 14.3% of BRAF+ had desmoplastic reaction (P=.02). The BRAF+ had a lower absorbed dose than the administered activity (5.4Gy/MBq vs 20Gy/MBq, P=.02); lower% activity with respect to the unit of mass at 2 (0.046%/g vs 0.103%/g, P=.02) and at 7days (0.006%/gr vs 0.034%/gr, P=.04) CONCLUSIONS: The mutation of the BRAF V600E gene is related with greater resistance to postoperative treatment with ¹³¹I since the onset of the disease.

Theranostic radiopharmaceuticals: established agents in current use

Although use of the term "theranostic" is relatively recent, the concept goes back to the earliest days of nuclear medicine, with the use of radioiodine for diagnosis and therapy of benign and malignant thyroid disease being arguably the most successful molecular radiotherapy in history. A diagnostic scan with ¹²³I-, ¹²⁴I-, or a low activity of ¹³¹I-iodide is followed by therapy with high activity ¹³¹I-iodide. Similarly, adrenergic tumours such as phaeochromocytoma and neuroblastoma can be imaged with ¹²³I-metaiodobenzylguanidine and treated with ¹³¹I-metaiodobenzylguanidine. Bone scintigraphy can be used to select patients with painful bone metastases from prostate cancer who may benefit from treatment with beta- or alpha-particle emitting bone seeking agents, the most recent and successful of which is ²²³Ra radium chloride. Anti-CD20 monoclonal antibodies can be used to image and treat non-Hodgkins lymphoma, though this has not been as commercially successful as initially predicted. More recently established theranostics include somatostatin receptor targeting peptides for diagnosis and treatment of neuroendocrine tumours with agents such as ⁶⁸Ga-DOTATATE and ¹⁷⁷Lu-DOTATATE, respectively. Finally, agents which target prostate-specific membrane antigen are becoming increasingly widely available, despite the current lack of a commercial product. With the recent licensing of the somatostatin peptides and the rapid adoption of ⁶⁸Ga- and ¹⁷⁷Lu-labelled prostate-specific membrane antigen targeting agents, we have built upon the experience of radioiodine and are already seeing a great expansion in the availability of widely accepted theranostic radiopharmaceuticals.

Radioiodine ablation in thyroid cancer patients: renal function and external radiation dose rate at discharge according to patient preparation

BACKGROUND

An elevated thyroid stimulating hormone (TSH) level is essential for the uptake of radioiodine into thyroid remnants and residual thyroid cancer in patients undergoing high-dose radioiodine therapy (HD-RIT). Recently, the use of recombinant human thyroid stimulating hormone (rh-TSH) has increased in preference over the conventional method of thyroid hormone withdrawal (THW). However, the clinical influences of the two methods, aside from the therapeutic effects, have not been widely evaluated. The aim of this work was to investigate the influences of the two methods, particularly on the renal function and external radiation dose rate (EDR) from patients undergoing HD-RIT.

METHODS

From February 2012 to November 2016, 667 patients (M:F=138:529, mean age: 47.7±11.8 years), who underwent first HD-RIT (120, 150, or 180 mCi, 1 mCi=37 MBq) for ablation of remnant thyroid tissue or residual thyroid cancer, were enrolled. Patients who were proven to have distant metastasis to lung or bone were excluded. Low- to high-risk patients based on 2015 American thyroid association management guidelines who underwent first HD-RIT in our department were included. The period from total thyroidectomy to HD-RIT was limited within 12 months. The following parameters were collected and evaluated: age, gender, histology type and TNM stage of thyroid cancer, glomerular filtration rate on the admission day for total thyroidectomy (baseline GFR), GFR on the day of HD-RIT (follow-up GFR), thyroglobulin (Tg) and TSH levels on the day of HD-RIT, and EDR on the discharge day after HD-RIT.

RESULTS

There were 386 patients using the THW method and 281 patients choosing the rh-TSH method. The baseline GFR of the THW group (106±16 mL/min/1.73 m2) and that of the rh-TSH group (104±17 mL/min/1.73 m2) were within normal limits and there was no significant difference. However, follow-up GFR of the THW group (84±17 mL/min/1.73 m2) was much lower than that of the rh-TSH group (104±16 mL/min/1.73 m2) (P=0.000). In the THW group, the follow-up GFR decreased significantly (P=0.000), yet the follow-up GFR of the rh-TSH group was not statistically different when compared with its baseline GFR (P=0.142). EDRs were lower in all rh-TSH subgroups compared to those of THW subgroups with statistical significance. Tg and TSH levels were not different between the two groups, excluding a few small-sized subgroups analyses.

CONCLUSIONS

In this retrospective analysis of renal function and EDR, the use of rh-TSH appears to help maintain renal function and finally decrease EDR in contrast to the THW method when undergoing HD-RIT.

Could short thyroid hormone withdrawal be an effective strategy for radioiodine remnant ablation in differentiated thyroid cancer patients?

PURPOSE

Current guidelines recommend thyroid hormone withdrawal (THW) of 3-4 weeks before radioiodine remnant ablation (RRA) of differentiated thyroid carcinoma (DTC). We aimed to evaluate (1) the reliability of a shorter THW (i.e., 14 days) to achieve adequate TSH levels (i.e., 30 mU/l), (2) the association between length of THW and response to therapy, and (3) the potential association between pre-ablation TSH levels and patients' outcome.

METHODS

After thyroidectomy, all patients started LT4 therapy, which was subsequently discontinued in order to perform RRA. Patients were broken down into two groups according to the length of THW: group A, 2 weeks of THW, and group B, 3-4 weeks of THW. We used clinical, biochemical, and imaging data to evaluate patients' outcome. By means of univariate and multivariate analysis, including main DTC prognostic factors, we assessed the impact of THW length and TSH levels on patients' outcome.

RESULTS

We evaluated 222 patients, 85 of whom were treated with RRA after a THW period of 2 weeks (group A). All other 137 patients underwent RRA after 3-4 weeks THW (group B). At the time of RRA all patients presented TSH levels ≥30 mU/l. After a median follow-up time of 3.4 years, we found 183 patients (82%) with excellent response to treatment and 39 patients (18%) showing incomplete response. Kaplan-Meier response to therapy curves showed that ablation-Tg, tumor size, and lymph node status were significantly associated with prognosis; no associations were found between THW length, TSH levels, and prognosis. Multivariate Cox model showed that only ablation-Tg was significantly associated with treatment response.

CONCLUSIONS

Prior to RRA, a short 2-week THW is an effective method to stimulate TSH levels. No difference in terms of incomplete response to treatment was observed between DTC patients prepared for RRA with a short THW and those with the long THW.

Multicentre clinical evaluation of the new highly sensitive Elecsys® thyroglobulin II assay in patients with differentiated thyroid carcinoma

OBJECTIVE

A highly sensitive thyroglobulin assay (Elecsys® Tg II, Roche Diagnostics, Penzberg, Germany) has become available for monitoring patients with differentiated thyroid cancer (DTC). Here, we evaluated the clinical performance of Elecsys® Tg II assay in a multicentre patients series and compare it with the established Access® Tg assay (Beckman Coulter, Brea, CA, USA).

DESIGN

Retrospective analysis on prospectively selected patients in four thyroid cancer referral centres with uniform DTC management.

PARTICIPANTS

All DTC cases diagnosed, treated and followed up in four tertiary referral centres for thyroid cancer since January 2005 (n = 1456) were retrieved, and predefined selection criteria were applied to prevent relevant enrolment biases. A series of 204 patients was finally selected for this study.

MEASUREMENTS

Samples had been stored at -80°C. Tg was measured by fully automated immunometric Elecsys® Tg II and Access® Tg assays in a centralized laboratory.

RESULTS

Two hundred and four DTC were finally included. Of these, 10.8% had structural recurrence (sREC), and 81.4% showed no evidence of disease (NED) at the end of follow-up. There was a significant analytical bias between methods that cannot be used interchangeably. Using ROC curve analysis, the best basal and rhTSH-stimulated Tg cut-offs to detect sREC were 0.41 μg/L and 1.82 μg/L for Elecsys® and 0.36 μg/L and 1.62 μg/L for Access® assay, respectively. Using Cox proportional hazard regression, Tg was the only independent predictor of cancer relapse.

CONCLUSIONS

Using appropriate assay-specific cut-offs, the clinical performance of the Elecsys® Tg II assay was comparable to that provided by the well-established Access® Tg assay.

Thyroid Cancer: Risk-Stratified Management and Individualized Therapy

Thyroid cancer is the most common endocrine malignancy. Differentiated thyroid cancer (DTC) with the two subtypes, papillary thyroid cancer (PTC) and follicular thyroid cancer (FTC), is the most frequent subtype of thyroid cancer; more rare subtypes are medullary thyroid cancer (MTC) and anaplastic thyroid cancer (ATC). The incidence of DTC has increased rapidly in recent years due to the more frequent use of imaging methods such as ultrasound of the neck and fine-needle aspiration (FNA) of thyroid nodules. After total thyroidectomy and radioiodine treatment, DTC remains an indolent and curable disease in most patients, whereas the cure rate in MTC is lower and depends on early diagnosis. Most ATCs are incurable. In recent years, there has been great progress in identifying genetic changes in thyroid cancer, and genetic testing of FNA samples or blood samples provides useful information for clinical decision making. Tumor staging, either postoperatively or by imaging, and measuring the tumor markers thyroglobulin for DTC and calcitonin for MTC, allow for dynamic risk-adapted stratification for follow-up procedures. In advanced metastatic thyroid cancer, molecular targeted therapy using tyrosine kinase receptor inhibitors, including sorafenib, lenvantinib, vandetanib, and cabozantinib, helps control tumor progression and prolongs progression-free survival. Using a dynamic risk-stratified approach to manage thyroid cancer, the outcomes for most thyroid cancer patients are excellent compared with those for other cancers. The major challenge in the future is to identify high-risk patients and to treat and monitor them appropriately. Clin Cancer Res; 22(20); 5012-21. ©2016 AACR SEE ALL ARTICLES IN THIS CCR FOCUS SECTION, "ENDOCRINE CANCERS REVISING PARADIGMS".