Dosimetry-guided high-activity 131I therapy in patients with advanced differentiated thyroid carcinoma: initial experience

Radioiodine Therapy in Pediatric Differentiated Thyroid Cancer: Dosimetry, Clinical Care, and Future Challenges

ABSTRACT

Thyroid cancer is very rare in children. 131 I therapy after thyroidectomy is established in pediatric differentiated thyroid cancer (DTC). Pediatric DTC guideline is silent on the optimum amount of 131 I that could be safely and effectively administered to children who are more radiosensitive. Like adult DTC, children are also given 131 I therapy empirically based either on age or body weight. Pediatric DTC guideline recommends that patient-specific dosimetry is important in children. Still, due to the low incidence rate and the practical difficulties of dosimetry, it has neither been established nor adopted in routine practice. This review article aims to discuss current approaches of 131 I therapy in children and young adult patients with DTC and dosimetric data obtained by several investigators. Efforts are required to simplify dosimetric procedures and precise results, especially in determining lesion size. We prefer 3-dimensional dosimetry over planar dosimetry, where lesion size could be measured accurately. 124 I PET/CT-based dosimetry is expected to give accurate dosimetric results. The most challenging aspect is that no randomized controlled trials are available to compare the empiric 131 I therapy results versus dosimetry-based treatment outcomes in children and young adults. Suppose dosimetry-based 131 I therapy could be shown to have better outcomes, namely, successful ablation rate, better disease-free survival, and lesser treatment-emergent adverse events than empirical 131 I treatment. In that case, one can argue in favor of the former. Unfortunately, no convincing study is currently available. Thus, there is a need for a randomized control trial to settle this issue.

Radioiodine therapy in the different stages of differentiated thyroid cancer

Differentiated thyroid cancer is the most frequent type of thyroid cancer with an increasing incidence in the last decades. The initial management is represented by surgical treatment followed by radioactive iodine therapy that includes remnant ablation, adjuvant treatment or treatment of metastatic disease. Radioactive iodine treatment is performed only in selected cases based on the risk of recurrence and mortality during follow up, according to American Joint Committee on Cancer Union for international Cancer Control Tumor, Node, Metastasis (AJCC/TNM) staging system and the 2015 American Thyroid Association (ATA) risk stratification system. This article will review the key factors to consider when planning radioactive iodine therapy in differentiated thyroid cancer patients after surgery and during follow up.

Correlation analysis of I-131 SPECT/CT uptake parameters with the success ablation treatment of thyroid remnant in patients with low-intermediate-risk differentiated thyroid cancer

OBJECTIVE

To predict the successful outcome of radioactive iodine-131 (I-131) ablation treatment for differentiated thyroid cancer (DTC) patients using quantitative parameters from therapeutic I-131 SPECT/CT.

METHODS

This retrospective study enrolled 145 DTC patients (41 males and 104 females) who had radioactive iodine-131 (I-131) (RAI) ablation therapy following thyroidectomy surgery from July 2020 to May 2021. The median age was 47 years (24-65 years). All the patients underwent therapeutic I-131 thyroid SPECT/CT scan after RAI ablation. The I-131 uptake quantitative parameters SUV max , SUV mean %ID and ∆Tg (defined as the Tg level before RAI ablation minus the Tg level after six months) were assessem. Successful ablation treatment was defined as the level of TSH-stimulated Tg≤1 ng/mL and the disappearance of the thyroid bed on a whole-body I-131 scan six months or later after ablation treatment.

RESULTS

The quantitative parameters from therapeutic I-131 SPECT/CT of the successful ablation (n=130) group with SUV max 7.74 (3.84, 18.78) g/ml, SUV mean 4.02 (2.11, 6.39) g/ml and %ID 2.21% (0.67%, 7.30%) were significantly higher than those of the unsuccessful (n=15) group 0.75 (0.53, 1.28) g/ml, 0.44 (0.29, 0.79) g/ml and 0.16% (0.06%, 1.48%) (Z=-5.87, -5.71 and -4.99, all P < 0.001). SUV max , SUV mean and %ID were positively correlated with ΔTg (all P < 0.001). Receiver operating characteristics curve analysis showed that %ID performed better predict value than either SUV max (AUC=0.914, and 0.874, P=0.009) or SUV mean (AUC= 0.863 P=0.002). SUV max , SUV mean and%ID (OR =1.50, 2.85 and 1.01 all P < 0.001) were all independent predictors of successful RAI ablation.

CONCLUSION

The quantitative parameters of therapeutic I-131 SPECT/CT were related to the efficacy of ablation treatment, and %ID could predict the successful outcome of ablation treatment for DTC patients.

Randomised comparison of 1.1 GBq and 3.7 GBq radioiodine to ablate the thyroid in the treatment of low-risk thyroid cancer: a 13-year follow-up

Purpose: The optimal activity of radioiodine (I-131) administered for ablation therapy in papillary and follicular thyroid cancer after thyroidectomy remains unknown in a long-term (> 10 year) follow-up. Some, shorter follow-up studies suggest that activities 1.1 GBq and 3.7 GBq are equally effective. We evaluated the long-term outcomes after radioiodine treatment to extend current knowledge about the optimal ablative dose of I-131.Methods: One hundred and sixty consecutive adult patients (129 females, 31 males; mean age 46 ± 14 y, range 18-89 y) diagnosed with histologically confirmed differentiated thyroid cancer, were randomised in a prospective, phase III, open-label, single-centre study, to receive either 1.1 GBq or 3.7 GBq of I-131 after thyroidectomy. At randomisation, patients were stratified according to the histologically verified cervical lymph node status and were prepared for ablation using thyroid hormone withdrawal. No uptake in the whole-body scan with I-131 and serum thyroglobulin concentration less than 1 ng/mL at 4-8 months after treatment was considered successful ablation.Results: Median follow-up time was 13.0 years (mean 11.0 ± 4.8 y; range 0.3-17.1 y). Altogether 81 patients received 1.1 GBq with successful ablation in 45 (56%) patients. In the original study, thirty-six patients (44%) needed one or more extra administrations to replete the ablation. Of these, 4 (8.9%) and 5 (14%) patients relapsed during the follow-up, respectively. Of the 79 patients treated with 3.7 GBq 45 (57%) had successful ablation after one administration of radioiodine and 34 (43%) needed several treatments. Of these, 2 (4.4%) and 9 (26.5%) patients relapsed, respectively. The groups did not differ in the proportion of patients relapsing (p = .591).Conclusion: During follow-up of median 13 years, 3.7 GBq is not superior to 1.1 GBq in the radioiodine treatment after thyroidectomy in papillary and follicular thyroid cancer.

Bone marrow suppression in pediatric patients with differentiated thyroid cancer following empirical radioiodine therapy

Pediatric patients with differentiated thyroid cancer (DTC) tend to have more advanced disease at presentation, for which more aggressive radioiodine (RAI) treatment would be commonly recommended. Several previous studies recommended dosimetry to calculate the optimal activity of RAI in pre-pubertal children and in children with a significant distant metastasis. This study aimed to evaluate the effect of empirical RAI treatment for DTC on bone marrow function in pre-pubertal children and adolescents.DTC patients aged ≤ 18 years receiving empirical RAI treatment with complete blood count data before and after treatment were included and divided into pre-pubertal and pubertal groups. Blood count values at baseline and 1.5-3 months, 3-6 months, and 6-12 months after RAI treatment were compared. The effect of demographic, clinical, and laboratory variables on bone marrow function were assessed.We included 83 patients (113 treatments). At diagnosis, pre-pubertal children had more aggressive tumor features, including tumor size (P = .045) and distant metastases (P = .037). Approximately 51% to 96% of hypocellular bone marrow, and 11% to 14% of anemia were observed in the pre-pubertal and pubertal groups, with a majority of mild (Grade 1-2) and minority of moderate (Grade 3) bone marrow suppression. No significant differences in bone marrow function or Common Terminology Criteria for Adverse Events (CTCAE) grades were found between the pre-pubertal and pubertal groups after RAI treatment. None of the clinical factors tested were found to be significant predictors for bone marrow suppression after RAI treatment.Empirical RAI treatment for DTC in pre-pubertal children and adolescents causes mild to moderate bone marrow suppression with limited clinical significance. With adequate preparations for RAI treatment, empirical high activities (150-200 mCi) could be safe and well tolerated by both pre-pubertal and pubertal patients with DTC.

Individualized dosimetry in children and young adults with differentiated thyroid cancer undergoing iodine-131 therapy

Objectives The amount of Iodine-131 to treat young patients with differentiated thyroid cancer (DTC) has not been established so far. The purpose of this study was to perform and compare blood dosimetry by "Hanscheid's approach"and lesion dosimetry by "Maxon's approach". Methods Seventy-one DTC patients ≤21 years were given diagnostic activity of 74 MBq 131I followed by whole-body scan (WBS) at 2 h (pre-void), 24 h, 48 h, and ≥72 h. Pre-therapy blood and lesion dosimetry were conducted to determine the absorbed doses to blood and lesions and to predict the therapeutic activity. The administered activities were varied from 1.11-5.55 GBq of 131I depending on disease extent. Post therapy dosimetries were again performed by acquiring WBS data at 24 h, 48 h, and ≥72 h. Results In blood dosimetry, the difference between predicted therapy activity (PTA) and actual therapeutic activity (ATA) was statistically significant in remnant and lung lesions but insignificant in nodal metastases (p=0.287). In lesion dosimetry, the difference between PTA and ATA was statistically significant for lung metastasis patients; however, not significant in remnant (p=0.163) and nodal metastases (p=0.054). The difference between predicted and observed absorbed dose was insignificant in blood dosimetry whereas, significant in lesion dosimetry. Conclusions The PTA based on 0.3 Gy recommendations of Hanscheid et al. may be adequate for patients with remnant or nodal metastases but inadequate for lung metastases. Lesion dosimetry demonstrated that there is scope to decrease the 131I empiric ATA for remnant and nodal metastases; at the same time, there is scope to increase in lung metastasis patients.

Initial treatment of pediatric differentiated thyroid cancer: a review of the current risk-adaptive approach

Differentiated thyroid cancer in children is a rare disease, accounting for only 1.4% of all pediatric malignancies. The diagnosis, biological behavior and treatment of differentiated thyroid cancer in children is different from that in adults. While there are many unresolved issues regarding approaches to management of differentiated thyroid cancer in the pediatric population, there is near universal consensus that treatment of this disease, which includes total thyroidectomy, central lymph node dissection at the time of initial surgery in those with nodal metastases, and the possible use of iodine-131 radiotherapy, is best performed by specialists including high-volume endocrine surgeons and experts with experience in calculating and administering radioactive iodine in children, when deemed appropriate.

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.

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.

Perspectives for Concepts of Individualized Radionuclide Therapy, Molecular Radiotherapy, and Theranostic Approaches

Radionuclide therapy (RNT) stands on the delivery of radiation to tumors or non-tumor target organs using radiopharmaceuticals that are designed to have specific affinity to targets. RNT is recently called molecular radiotherapy (MRT) by some advocators in order to emphasize its characteristics as radiotherapy and the relevance of dosimetry-guided optimization of treatment. Moreover, RNT requires relevant radiation protection standards because it employs unsealed radionuclides and gives therapeutic radiation doses in humans. On the basis of these radiation protection standards, the development and use of radiopharmaceuticals for combined application through diagnostics and therapeutics lead to theranostic approaches that will enhance the efficacy and safety of treatment by implementing dosimetry-based individualization.

Lesion-Wise Comparison of Pre-Therapy and Post-Therapy Effective Half-Life of Iodine-131 in Pediatric and Young Adult Patients with Differentiated Thyroid Cancer Undergoing Radioiodine Therapy

Purpose

The effective half-life of radioiodine is an important parameter for dosimetry in differentiated thyroid cancer patients, particularly in children. We determined the pre-therapy and post-therapy effective half-life in different types of lesions, i.e., remnant, node, or lung metastases.

Methods

Of 84 patients recruited, 27 were < 18 years (group 1) and the remaining 57 were between 18 and 21 years (group 2). A total of 114 studies were conducted and 253 lesions were analyzed. Serial whole-body scans were acquired at 24, 48, and ≥ 72 h after administration of iodine-131. Region of interests was drawn over lesions to determine counts in the lesion. Time versus counts graphs were plotted and mono-exponentially fitted to determine effective half-life.

Results

The post-therapy effective half-life was found to be lesser than pre-therapy effective half-life in all types of lesions and in all groups. Median effective half-life was found maximum in intact lobe, minimum in the lung, and intermediate in remnant and nodes. In the assessment of all lesions together, pre- and post-therapy median and interquartile range (IQR) effective half-life were 59.8 (37-112) h and 48.6 (35.2-70.8) h (p < 0.0001) in group 1, 73.9 (46.2-112.7) h and 60 (57.4-85.9) h (p < 0.0001) in group 2, and 68.6 (41.53-112.36) h and 54.7 (36-80.6) h (p < 0.0001) in combined group, respectively. Importantly, the pre- and post-therapy median effective half-life serially dropped after each successive cycles of iodine-131.

Conclusions

There was a significant difference in pre-therapy and post-therapy effective half-life in all types of lesions. These results may have implications in calculating the correct therapeutic dose in children and in young adults.

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.

Low or Undetectable Basal Thyroglobulin Levels Obviate the Need for Neck Ultrasound in Differentiated Thyroid Cancer Patients After Total Thyroidectomy and 131I Ablation

BACKGROUND

Neck ultrasound (NUS) is currently seen as a main component of follow-up of differentiated thyroid cancer (DTC) and is usually performed regardless of non-stimulated thyroglobulin (Tg) levels. The aim of this study was to determine whether there is a clinical benefit from such a routine NUS in DTC patients.

METHODS

A retrospective database study was conducted of 3176 cervical ultrasound exams performed in 773 patients between June 15, 1996, and July 1, 2012. The accuracy of ultrasound results was assessed based on the results of further diagnostic and/or therapeutic procedures within six months of a particular ultrasound.

RESULTS

A total of 2199 NUS exams were classified as true negative, 216 as true positive, 692 as false positive in 339 (43.9%) individual patients, 170 of whom were low risk, and 69 as false negative. Thus, overall sensitivity, specificity, positive predictive value, negative predictive value, and accuracy [confidence interval] were 75.8% [70.1-81.5%], 76.1% [74.3-77.8%], 23.8% [18.1-29.5%], 97.0 [96.2-97.7%], and 76.0% [74.3-77.7%], respectively. No significant differences were found between low- and high-risk patients. There were no significant differences between patients with an undetectable and a low detectable (<1 μg/L) Tg level. However, these two groups both showed significantly lower positive predictive value and higher negative predictive value than patients with a Tg ≥1 μg/L. From January 2007 onwards, true-positive and false-negative neck ultrasounds were no longer observed in patients with Tg <1 μg/L.

CONCLUSION

After total thyroidectomy and ¹³¹I ablation, neck ultrasound should be reserved only for anti-Tg antibody negative patients with a Tg level of ≥1 μg/L.

Variations in the practice of molecular radiotherapy and implementation of dosimetry: results from a European survey

BACKGROUND

Currently, the implementation of dosimetry in molecular radiotherapy (MRT) is not well investigated, and in view of the Council Directive (2013/59/Euratom), there is a need to understand the current availability of dosimetry-based MRT in clinical practice and research studies. The aim of this study was to assess the current practice of MRT and dosimetry across European countries.

METHODS

An electronic questionnaire was distributed to European countries. This addressed 18 explicitly considered therapies, and for each therapy, a similar set of questions were included. Questions covered the number of patients and treatments during 2015, involvement of medical specialties and medical physicists, implementation of absorbed dose planning, post-therapy imaging and dosimetry, and the basis of therapy prescription.

RESULTS

Responses were obtained from 26 countries and 208 hospitals, administering in total 42,853 treatments. The most common therapies were 131I-NaI for benign thyroid diseases and thyroid ablation of adults. The involvement of a medical physicist (mean over all 18 therapies) was reported to be either minority or never by 32% of the responders. The percentage of responders that reported that dosimetry was included on an always/majority basis differed between the therapies and showed a median value of 36%. The highest percentages were obtained for 177Lu-PSMA therapy (100%), 90Y microspheres of glass (84%) and resin (82%), 131I-mIBG for neuroblastoma (59%), and 131I-NaI for benign thyroid diseases (54%). The majority of therapies were prescribed based on fixed-activity protocols. The highest number of absorbed-dose based prescriptions were reported for 90Y microsphere treatments in the liver (64% and 96% of responses for resin and glass, respectively), 131I-NaI treatment of benign thyroid diseases (38% of responses), and for 131I-mIBG treatment of neuroblastoma (18% of responses).

CONCLUSIONS

There is a wide variation in MRT practice across Europe and for different therapies, including the extent of medical-physicist involvement and the implementation of dosimetry-guided treatments.

Early and late adverse effects of radioiodine for pediatric differentiated thyroid cancer

BACKGROUND

Radioiodine-131 (I131) therapy for differentiated thyroid cancer (DTC) is generally a safe and effective treatment, but it has some potential side effects, which have been well described in adults but less analyzed in children. Our aim was to describe early and late adverse events of radioactive I131 in pediatric patients.

METHODS

All consecutive patients ≤18 years treated for DTC in the period 1980-2015 were retrospectively analyzed for early and late side effects of radioiodine. Early side effects include nausea/emesis, radiation thyroiditis, sialadenitis, dry mouth, and transient bone marrow (BM) suppression. Late complications include permanent salivary gland dysfunction, permanent BM suppression, pulmonary fibrosis, second cancers, and fertility problems.

RESULTS

One hundred five pediatric patients were treated with I131 for DTC in our department for a total amount of 302 radioiodine treatments. In total, 127 early complications were recorded: 44 episodes of nausea/emesis; 30 sialoadenitis, 24 thyroiditis, 18 dry mouth, and 11 transient BM suppression. Early side effects were correlated with the amount of radioactivity administered in any treatment. Twelve children developed ≥1 late complication for a total of 20 complications: two permanent salivary gland dysfunction, four permanent BM suppression, five pulmonary fibrosis, four second malignancies, and five fertility alterations. Late events, except fertility alterations, were correlated with the number of therapies and cumulative activities of I131.

CONCLUSIONS

In conclusion, early side effects of I131 are associated with the amount of administrated activities of each treatment, while the late effects are correlated with the number of treatments and cumulative activities of radioiodine, except for fertility problems.

131I-MIBG Therapy in a Metastatic Small Bowel Neuroendocrine Tumor Patient Undergoing Hemodialysis

Systemic radioisotope therapy with I-metaiodobenzylguanidine (I-MIBG) is an effective form of targeted therapy for neuroendocrine tumors. One of the absolute contraindications to administering I-MIBG therapy listed in the 2008 European Association of Nuclear Medicine guidelines is renal insufficiency requiring dialysis, although this contraindication is not evidence based. We describe a 68-year-old woman with a metastatic small bowel neuroendocrine tumor who developed renal insufficiency requiring hemodialysis. Imaging and dosimetry with I-MIBG were performed and showed that the radiation doses to the whole body and lungs were within safe limits. She was treated with 1820 MBq of I-MIBG with no short-term adverse reactions.

Pediatric papillary thyroid cancer: current management challenges

Although with a standardized incidence of 0.54 cases per 100,000 persons, differentiated thyroid cancer (DTC) is a rare disease in children and adolescents, it nonetheless concerns ~1.4% of all pediatric malignancies. Furthermore, its incidence is rising. Due to the rarity and long survival of pediatric DTC patients, in most areas of treatment little evidence exists. Treatment of pediatric DTC is therefore littered with controversies, many questions therefore remain open regarding the optimal management of pediatric papillary thyroid cancer (PTC), and many challenges remain unsolved. In the present review, we aim to provide an overview of these challenging areas of patient and disease management in pediatric PTC patients. Data on diagnosis, surgery, radionuclide, and endocrine therapy are discussed, and the controversies therein are highlighted.

Management of Differentiated Thyroid Cancer in Children: Focus on the American Thyroid Association Pediatric Guidelines

First introduced in 1946, radioactive iodine (I-131) produces short-range beta radiation with a half-life of 8 days. The physical properties of I-131 combined with the high degree of uptake in the differentiated thyroid cancers (DTCs) led to the use of I-131 as a therapeutic agent for DTC in adults. There are two indications for the potential use of I-131 therapy in pediatric thyroid disorders: nonsurgical treatment of hyperthyroidism owing to Graves' disease and the treatment of children with intermediate- and high-risk DTC. However, children are not just miniature adults. Not only are children and the pediatric thyroid gland more sensitive to radiation than adults but also the biologic behavior of DTC differs between children and adults as well. As opposed to adults, children with DTC typically present with advanced disease at diagnosis; yet, they respond rapidly to therapy and have an excellent prognosis that is significantly better than that in adult counterparts with advanced disease. Unfortunately, there are also higher rates of local and distant disease recurrence in children with DTC compared with adults, mandating lifelong surveillance. Further, children have a longer life expectancy during which the adverse effects of I-131 therapy may become manifest. Recognizing the differences between adults and children with DTC, the American Thyroid Association commissioned a task force of experts who developed and recently published a guideline to address the unique issues related to the management of thyroid nodules and DTC in children. This article reviews the epidemiology, diagnosis, staging, treatment, therapy-related effects, and suggestions for surveillance in children with DTC, focusing not only on the differences between adults and children with this disease but also on the latest recommendations from the inaugural pediatric management guidelines of the American Thyroid Association.

Thyroid Cancer in Pediatrics

Well differentiated thyroid cancer (DTC) in children is characterized by a high rate of response to treatment and low disease-specific mortality. Treatment of children with DTC has evolved toward a greater reliance on evaluation and monitoring with serial serum thyroglobulin measurements and ultrasound examinations. Radioiodine therapy is recommended for thyroid remnant ablation in high-risk patients, treatment of demonstrated radioiodine-avid local-regional disease not amenable to surgical resection, or distant radioiodine-avid metastatic disease. Sufficient time should be given for benefits of radioiodine therapy to be realized, with follow-up monitoring. Re-treatment with radioiodine can be deferred until progression of significant disease manifests.

The TNM system (version 7) is the most accurate staging system for the prediction of loss of life expectancy in differentiated thyroid cancer

OBJECTIVE

Many prognostic systems have been developed for differentiated thyroid cancer. It is unclear which one of these performs 'best'. Our aim was to compare staging systems applicable to our patient database to identify which best predicts DTC-related loss of life expectancy and DTC-specific mortality.

DESIGN

Database study of patients with DTC treated in our centre between 1978 (earliest available data) up to and including 1 July 2014. All were staged in accordance with the AMES, Clinical Class, Memorial Sloan Kettering, Ohio State University, TNM versions 5 and 6/7, University of Alabama, University of Münster and qTNM systems.

PATIENTS

A total of 2257 patients with differentiated thyroid cancer.

MEASUREMENTS

Loss of life expectancy expressed as relative survival and 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

Median available follow-up time was 7·2 years (range: 0-35·1 years). Three hundred and twenty-seven patients died, 149 of whom died of DTC. Version 7 of the TNM system was best for predicting DTC-related mortality (P = 7·1 × 10^-52 ; PVE = 0·296), followed by TNM version 5 (P = 6·7 × 10^-44 ; PVE = 0·255). For prediction of loss of life expectancy, version 7 of the TNM system was also best, closely followed by the Clinical Class system (P both < 2 × 10^-16 ).

CONCLUSIONS

The UICC/AJCC TNM system version 7 outperforms other prognostic classification systems based on extent of disease at the start of treatment both for prediction of differentiated thyroid cancer-related death and for prediction of loss life expectancy.

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.

Pretherapeutic dosimetry in patients affected by metastatic thyroid cancer using 124I PET/CT sequential scans for 131I treatment planning

PURPOSE

This study evaluates the use of sequential I PET/CT for predicting absorbed doses to metastatic lesions in patients with differentiated thyroid cancer undergoing I therapy.

METHODS

From July 2011 until July 2013, 30 patients with metastatic differentiated thyroid cancer were enrolled. Each participant underwent PET/CT at 4, 24, 48, and 72 hours with 74 MBq of I. Blood samples and whole-body exposure measurements were obtained to calculate blood and red marrow doses. Activity concentrations and lesion volumes obtained from PET/CT were used to evaluate tumor doses with medical internal radiation dose formalism and spheres modeling. Mean administered I therapeutic dose was 5994 MBq (range, 1953-11,455 MBq).

RESULTS

I PET/CT demonstrated all lesions detected by posttherapy I whole-body scans. Mean dose rates for blood, red marrow, and lesions were as follows: 0.07 ± 0.02 mGy/MBq, 0.05 ± 0.02 mGy/MBq, and 46.5 ± 117 mGy/MBq, respectively. Despite the high level of thyroid-stimulating hormone and CT detectable lesions, 15 of 30 patients did not show any abnormal I uptake.

CONCLUSIONS

The quantitative value of I PET/CT allows simple and accurate evaluation of lesion dosimetry following medical internal radiation dose formalism. Negative I PET/CT predicts absence of iodine avidity, potentially allowing avoidance of therapeutically ineffective I administration.

Management Guidelines for Children with Thyroid Nodules and Differentiated Thyroid Cancer

BACKGROUND

Previous guidelines for the management of thyroid nodules and cancers were geared toward adults. Compared with thyroid neoplasms in adults, however, those in the pediatric population exhibit differences in pathophysiology, clinical presentation, and long-term outcomes. Furthermore, therapy that may be recommended for an adult may not be appropriate for a child who is at low risk for death but at higher risk for long-term harm from overly aggressive treatment. For these reasons, unique guidelines for children and adolescents with thyroid tumors are needed.

METHODS

A task force commissioned by the American Thyroid Association (ATA) developed a series of clinically relevant questions pertaining to the management of children with thyroid nodules and differentiated thyroid cancer (DTC). Using an extensive literature search, primarily focused on studies that included subjects ≤18 years of age, the task force identified and reviewed relevant articles through April 2014. Recommendations were made based upon scientific evidence and expert opinion and were graded using a modified schema from the United States Preventive Services Task Force.

RESULTS

These inaugural guidelines provide recommendations for the evaluation and management of thyroid nodules in children and adolescents, including the role and interpretation of ultrasound, fine-needle aspiration cytology, and the management of benign nodules. Recommendations for the evaluation, treatment, and follow-up of children and adolescents with DTC are outlined and include preoperative staging, surgical management, postoperative staging, the role of radioactive iodine therapy, and goals for thyrotropin suppression. Management algorithms are proposed and separate recommendations for papillary and follicular thyroid cancers are provided.

CONCLUSIONS

In response to our charge as an independent task force appointed by the ATA, we developed recommendations based on scientific evidence and expert opinion for the management of thyroid nodules and DTC in children and adolescents. In our opinion, these represent the current optimal care for children and adolescents with these conditions.

Determinants of successful ablation and complete remission after total thyroidectomy and ¹³¹I therapy of paediatric differentiated thyroid cancer

PURPOSE

In adult differentiated thyroid cancer (DTC) patients, successful ablation and the number of (131)I therapies needed carry a prognostic significance. The goal was to assess the prognosis of DTC in children and adolescents treated in our centre in relation to the number of treatments needed and to establish the determinants of both complete remission (CR) and successful ablation.

METHODS

Seventy-six DTC patients <21 years of age at diagnosis were included. Recurrence and death rates, rates of CR (=negative stimulated thyroglobulin, negative neck ultrasound and negative (131)I whole-body scintigraphy) and successful ablation (=CR after initial (131)I therapy) were studied.

RESULTS

No patients died of DTC. Seven patients were treated by surgery alone and did not show signs of recurrence during follow-up. Of the 69 patients also treated with (131)I therapy, 47 patients achieved CR, 25 of whom had successful ablation. In multivariate analysis, female gender and the absence of distant metastases were independent determinants of a higher CR rate. Female gender, lower T stage and higher (131)I activity (successful ablation, median activity 3.1 GBq, unsuccessful ablation 2.6 GBq) were determinants of a higher rate of successful ablation. After (131)I therapy no patient showed recurrence after reaching CR or disease progression if CR was not reached.

CONCLUSION

In our paediatric DTC population prognosis is extremely good with no deaths or recurrences occurring regardless of the number of (131)I therapies needed or whether CR was reached. The determinants of CR and successful ablation can be used to optimize the chance of therapy success.

Treatment planning in molecular radiotherapy

In molecular radiotherapy a radionuclide or a radioactively labelled pharmaceutical is administered to the patient. Treatment planning therefore comprises the determination of activity to administer. This administered activity should maximize tumour cell sterilization while minimizing normal tissue damage. In this work we present different approaches that are frequently used for determining the suitable activity. These approaches may be cohort- based as in chemotherapy, or patient-specific using dosimetry based on individual biokinetics. The approaches are different with respect to the input complexity, the corresponding costs and - in consequence - the quality of the therapy. In addition, a general scheme for data collection and analysis is proposed. To develop an effective and safe treatment, elaborate data need to be obtained. The main challenges, however, are collecting these complex data and analyse them properly.

Salivary glands ultrasound examination after radioiodine-131 treatment for differentiated thyroid cancer

BACKGROUND

The most important side effect of radioiodine ((131)I) therapy is sialoadenitis and xerostomy.

AIM

To evaluate by ultrasound (US) parotid and submandibular glands after (131)I therapy for differentiated thyroid cancer (DTC).

PATIENTS

Seventy-six subjects thyroidectomized for DTC submitted to salivary glands US examination. Forty-three of them had been previously treated with (131)I: 22 with 1.11 GBq (30 mCi) for remnant ablation, and 21 with higher doses [up to 44.4 GBq (1200 mCi)] for metastases. Thirty-three subjects studied before (131)I therapy served as controls. Parotid and submandibular volume, homogeneity, and echogenicity were determined. (131)I-treated patients filled a questionnaire about sialoadenitis symptoms.

RESULTS

Parotid gland volume was significantly higher in treated patients (28.3±16.2 ml) than in untreated patients (20.7±10.4 ml, p=0.0154) and related to the time from last (131)I therapy. Three had parotid volume <1.5 ml and complained severe xerostomy. Submandibular gland volume was similar in treated (11.2±7.6 ml) and untreated patients (8.6±4.2 ml, p=0.0602). Homogeneity and echogenicity were similar in treated and untreated patients. Sialoadenitis symptoms were reported in 26% and were related to the (131)I cumulative dose. Symptoms were not related to gland volume. Hypoechogenicity and inhomogeneity of the parotids were more frequent in patients with salivary stickiness.

CONCLUSION

Parotid, but not submandibular, volume is increased after (131)I treatment depending on the received activity and the time from irradiation but not on sialoadenitis symptoms. Xerostomy is associated to gland atrophy at US.

Update on thyroid cancer treatment

Surgery and radioiodine therapy are usually effective for most patients with differentiated thyroid cancer. However, poorly differentiated and anaplastic thyroid carcinomas represent a challenge to physicians on the basis of the current cancer treatment modalities. These cancer subtypes are often lethal and refractory to radioiodine therapy as well as most of the common chemotherapy drugs. Several kinase inhibitors are promising targeted therapies for these malignancies; however, clinical trials involving these drugs have provided controversial results and their clinical use is still under debate. Advanced medullary thyroid carcinomas may also be refractory to conventional therapies and novel kinase inhibitors may also be useful to control tumor progression in certain patients. Novel evidence is emerging that thyroid cancer is a stem cell disease, thereby implying that the driving force of thyroid cancers is a subset of undifferentiated cells (thyroid cancer stem cells) with unlimited growth potential and resistance to conventional therapeutic regimens. Thyroid cancer stem cells have been proposed as responsible for tumor invasiveness, metastasis, relapse and differentiation. Therefore, drugs that selectively target these cells could serve as a cornerstone in the treatment of poorly differentiated thyroid cancer.

The treatment of differentiated thyroid cancer in children: emphasis on surgical approach and radioactive iodine therapy

Pediatric thyroid cancer is a rare disease with an excellent prognosis. Compared with adults, epithelial-derived differentiated thyroid cancer (DTC), which includes papillary and follicular thyroid cancer, presents at more advanced stages in children and is associated with higher rates of recurrence. Because of its uncommon occurrence, randomized trials have not been applied to test best-care options in children. Even in adults that have a 10-fold or higher incidence of thyroid cancer than children, few prospective trials have been executed to compare treatment approaches. We recognize that treatment recommendations have changed over the past few decades and will continue to do so. Respecting the aggressiveness of pediatric thyroid cancer, high recurrence rates, and the problems associated with decades of long-term follow-up, a premium should be placed on treatments that minimize risk of recurrence and the adverse effects of treatments and facilitate follow-up. We recommend that total thyroidectomy and central compartment lymph node dissection is the surgical procedure of choice for children with DTC if it can be performed by a high-volume thyroid surgeon. We recommend radioactive iodine therapy for remnant ablation or residual disease for most children with DTC. We recommend long-term follow-up because disease can recur decades after initial diagnosis and therapy. Considering the complexity of DTC management and the potential complications associated with therapy, it is essential that pediatric DTC be managed by physicians with expertise in this area.

[Outcome of differentiated thyroid cancer after initial treatment]

Incidence of differentiated thyroid cancer has increased in the last two decades. This type of cancer is now being diagnosed at an earlier stage. Treatment strategy has been modified.

AIMS

The goals of this study were to analyze the outcome of differentiated thyroid cancer after initial treatment (surgery and radioiodine ablation) in patients evaluated and followed up in a single centre between l999 and 2009, to compare these results with others as well as to monitor the adoption of international recommendation. 107 patients having T1-T2 differentiated thyroid cancer were studied. Mean follow-up time was 63 months.

RESULTS

After surgery patients were prepared using thyroid hormone withdrawal or recombinant human thyrotropin, then 1.1-3.7 GBq 131-iodine was administered. First year evaluation consisted of ultrasound as well as serum thyrotropin and thyroglobulin (plus thyroglobulin antibody) determinations. Ablation success rate was 83% and the five year survival was 100%. There was not any cancer specific death.

CONCLUSION

In the future somewhat more radical surgery and less remnant ablation is needed with unified follow-up protocol.

Efficacy of dosimetric versus empiric prescribed activity of 131I for therapy of differentiated thyroid cancer

BACKGROUND

The optimal management of high-risk patients with differentiated thyroid cancer (DTC) consists of thyroidectomy followed by radioiodine ((131)I) therapy. The prescribed activity of (131)I can be determined using two approaches: 1) empiric prescribed activity of (131)I (E-Rx); and 2) dosimetry-based prescribed activity of (131)I (D-Rx).

AIM

The aim of the study was to compare the relative treatment efficacy and side effects of D-Rx vs. E-Rx.

METHODS

A retrospective analysis was performed of patients with distant metastases and/or locoregionally advanced radioiodine-avid DTC who were treated with either D-Rx or E-Rx. Response to treatment was based on RECIST (Response Evaluation Criteria in Solid Tumors) 1.1 criteria.

RESULTS

The study group consisted of 87 patients followed for 51 ± 35 months, of whom 43 were treated with D-Rx and 44 with E-Rx. Multivariate analysis, controlling for age, gender, and status of metastases revealed that the D-Rx group tended to be 70% less likely to progress (odds ratio, 0.29; 95% confidence interval, 0.087-1.02; P = 0.052) and more likely to obtain complete response (CR) compared to the E-Rx group (odds ratio, 8.2; 95% confidence interval, 1.2-53.5; P = 0.029). There was an association in the D-Rx group between the observed CR and percentage of maximum tolerable activity given as a first treatment of (131)I (P = 0.030). The advantage of D-Rx was specifically apparent in the locoregionally advanced group because CR was significantly higher in D-Rx vs. E-Rx in this group of patients (35.7 vs. 3.3%; P = 0.009). The rates of partial response, stable disease, and progression-free survival, as well as the frequency of side effects, were not significantly different between the two groups.

CONCLUSION

Higher efficacy of D-Rx with a similar safety profile compared to E-Rx supports the rationale for employing individually prescribed activity in high-risk patients with DTC.

Radioiodine for remnant ablation and therapy of metastatic disease

Radioiodine is considered an effective and low-risk therapy modality of advanced differentiated thyroid cancer. For patients without lymph-node or distant metastases and low stages of the primary tumor, debate is ongoing about the necessity of thyroid remnant tissue ablation in an adjuvant setting. On the basis of evidence from retrospective studies, and until results of ongoing controlled prospective randomized trials become available, (131)I ablation of remnant thyroid tissue in patients with primary tumors >1 cm is advisable. For thyroid remnant ablation, individual dosimetry is not obligatory. By contrast, the effectiveness of (131)I therapy of locally advanced and/or metastatic disease can be improved by individual dosimetry. For practical reasons, an approach delivering the maximal possible radiation dose to the tumor without exceeding a critical blood dose of approximately 2 Gy seems advantageous. The availability of recombinant human TSH (rhTSH) has improved the quality of life of patients and reduces the radiation exposure of healthy nonthyroid tissue compared with TSH stimulation through levothyroxine withdrawal. In patients with distant metastases, rhTSH stimulation is possible only in off-label use, from which especially elderly and frail patients may benefit, as they most severely suffer from hypothyroidism caused by thyroid hormone withdrawal.