131I activity for remnant ablation in patients with differentiated thyroid cancer: A systematic review

Development of a predictive nomogram for intermediate-risk differentiated thyroid cancer patients after fixed 3.7GBq (100mCi) radioiodine remnant ablation

Objectives

The objective of this study was to develop a predictive nomogram for intermediate-risk differentiated thyroid cancer (DTC) patients after fixed 3.7GBq (100mCi) radioiodine remnant ablation (RRA).

Methods

Data from 265 patients who underwent total thyroidectomy with central lymph node dissection (CND) and received RRA treatment at a single institution between January 2018 and March 2023 were analyzed. Patients with certain exclusion criteria were excluded. Univariate and multivariate logistic regression analyses were performed to identify risk factors for a non-excellent response (non-ER) to RRA. A nomogram was developed based on the risk factors, and its performance was validated using the Bootstrap method with 1,000 resamplings. A web-based dynamic calculator was developed for convenient application of the nomogram.

Results

The study included 265 patients with intermediate-risk DTC. Significant differences were found between the ER group and the non-ER group in terms of CLNM>5, Hashimoto's thyroiditis, sTg level, TgAb level (P < 0.05). CLNM>5 and sTg level were identified as independent risk factors for non-ER in multivariate analysis. The nomogram showed high accuracy, with an area under the curve (AUC) of 0.833 (95% CI = 0.770-0.895). The nomogram's predicted probabilities aligned closely with actual clinical outcomes.

Conclusions

This study developed a predictive nomogram for intermediate-risk DTC patients after fixed 3.7GBq (100mCi) RRA. The nomogram incorporates CLNM>5 and sTg levels as risk factors for a non-ER response to RRA. The nomogram and web-based calculator can assist in treatment decision-making and improve the precision of prognosis information. Further research and validation are needed.

Ablation Rates and Long-Term Outcome Following Low-Dose Radioiodine for Differentiated Thyroid Cancer in the West of Scotland: A Retrospective Analysis

OBJECTIVE

Low-dose radioiodine is an accepted means of remnant ablation in patients with low- to intermediate-risk differentiated thyroid cancer (DTC) based on the results of several phase III trials. We evaluated the rate of ablation success and long-term recurrence outcomes in the first 3 years of implementing this practice at our institution.

METHODS

Patients who received 1.1 to 1.2 gigabecquerel (30 millicurie) were identified retrospectively from the radionuclide database, January 1, 2012, to December 31, 2014, inclusive. Successful ablation was defined as Iodine-131uptake <0.1% on diagnostic scan and Tg level <2.0 ng/mL at 6 to 8 months after treatment. Follow-up was conducted annually for 10 years and relapse rates were determined based on the available clinical, radiological, and biochemical information.

RESULTS

We identified 114 patients, 109 of whom had dual response assessment. The median age was 43 years (range, 14 to 80 years). Almost 70% had T1 or T2 tumors, with T3 and T4 tumors recorded in 27% and 2.5% of patients, respectively. Nodal staging was performed in just over 30% and involved lymph nodes were detected in 21% (N1a 8% and N1b 13%). Ablation success based on diagnostic scan alone was 94.7% (108/114), Tg alone 94.7% (108/114), and on both modalities was 90.4% (103/114).

CONCLUSION

Remnant ablation was achieved in >90%, and the corresponding clinical recurrence rate was only 1.8% despite the inclusion of patients with locally advanced disease. Low-dose radioiodine is effective and may be suitable for a proportion of patients with higher-risk DTC.

Correlation between remnant thyroid gland I-131 uptake and serum thyroglobulin levels: can we rely on I-131 whole body scans?

BACKGROUND

I-131 treatment (RAI) decision relies heavily on serum thyroglobulin (Tg) levels, as higher Tg levels are assumed to be correlated with higher I-131 uptake. Tg elevation, negative iodine scintigraphy (TENIS) definition is becoming more clinically relevant as alternative treatment methods are available. This study examined the correlation between Tg levels with I-131 uptake in remnant thyroid gland to evaluate the reliability of serum Tg levels in predicting I-131 uptake.

METHODS

From March 2012 to July 2019, 281 papillary thyroid cancer patients treated with 150 mCi RAI were retrospectively enrolled. Early (2nd day) and Delayed (7th day) post-RAI whole-body scan (WBS) neck counts were correlated with clinical and pathologic findings. Patients with normal neck ultrasound and undetectable level of serum Tg (< 0.2 ng/mL) and thyroglobulin antibody (TgAb) (< 10 IU/mL) were defined as ablation success within 2 years after I-131 ablation.

RESULTS

Thyroid gland weight, tumor size and thyroiditis were independent factors of preoperative serum Tg levels. Serum off-Tg levels correlated with Early and Delayed WBS neck counts, and thyroiditis pathology contributed to lower neck counts in both Early and Delayed WBSs. In multivariable analysis, Delayed WBS neck count, serum off-Tg and off-TgAb were significant factors for predicting ablation success.

CONCLUSION

I-131 uptake and retention in remnant thyroid gland correlates with serum off-Tg levels, thyroiditis, and ablation success in thyroid cancer patients receiving high-dose I-131 therapy. Semi-quantitative I-131 analysis with Early and Delayed WBSs provides additional information in evaluating ablation success, with the potential application for metastasis treatment response evaluation.

Factors Affecting Ablation Success After I-131 Radioactive Iodine Therapy in Low and Intermediate Risk Papillary Thyroid Cancer

The study was to evaluate the effect of radioactive iodine (RAI) treatment application time and clinical, histopathological factors on ablation success in patients with operated papillary thyroid cancer (PTC) in low and intermediate-risk. One hundred sixty-one patients with PTC in the low and intermediate-risk were evaluated. Most patients (89.4%) were in the low-risk, and 10.6% were in the intermediate-risk. When the patients were divided into two groups according to the date of receiving RAI treatment after surgery, those who received early treatment (≤3 months) constituted the majority of the patients (72.7%). Seventeen patients received 1.85 Gigabecquerel (GBq), 119 3.7 GBq, 25 5.55 GBq RAI. Most patients (82%) achieved ablation success after the first RAI treatment. The time interval between surgery and RAI treatment did not affect ablation success. Stimulated Tg level measured on the RAI treatment day was an independent predictive factor for successful ablation (p<0.001). The cut-off value of Tg found to predict ablation failure was 5.86 ng/ml. It was concluded that 5.55 GBq RAI treatment could predict ablation success compared to 1.85 GBq dose (p=0.017). It was concluded that having a T1 tumor may predict treatment success compared to a T2 or T3 tumor (p=0.001, p<0.001, retrospectively). The time interval does not affect ablation success in low and intermediate-risk PTC. The ablation success rate may decrease in patients who receive low-dose RAI and have high Tg levels before treatment. The most crucial factor in achieving ablation success is giving enough doses of RAI to ablate the residual tissue.

Analysis of Residence Time, Effective Half-Life, and Internal Dosimetry Before Radioiodine Therapy

Radioiodine therapy has been widely used for ablation of remnant tissue after surgical treatment of differentiated thyroid carcinoma (DTC). Internal dosimetry provides a new approach to choosing the administered activity-an approach that considers the distribution and retention of 131I individually per patient. This study used clinical techniques of internal dosimetry to assess the accumulated activity, internal bone marrow dosimetry, and effective half-life in patients undergoing treatment for DTC. Methods: This was a quantitative, retrospective study analyzing diagnostic documents and images. The internal dosimetry method calculated the dose absorbed by the bone marrow per administered activity of 131I. Calculation of the absorbed dose took into account the accumulated activity, which was obtained through measurements of whole-body images acquired at 4 intervals over 5 d. Results: The median dose absorbed by the bone marrow per administered activity was 0.117 mGy/MBq (range, 0.043-0.152 mGy/MBq). The median whole-body residence time was 22.0 h (range, 12.6-39.4 h). The median effective half-life was 15.6 h (range, 7.6-28.2 h). Conclusion: Internal dosimetry provides information relevant to safe dose limits for DTC radioiodine therapy, especially in advanced cases of the disease for which greater activities may be necessary.

Simulations of radioiodine exposure and protective thyroid blocking in a new biokinetic model of the mother-fetus unit at different pregnancy ages

In the case of nuclear incidents, radioiodine may be released. After incorporation, it accumulates in the thyroid and enhances the risk of thyroidal dysfunctions and cancer occurrence by internal irradiation. Pregnant women and children are particularly vulnerable. Therefore, thyroidal protection by administering a large dose of stable (non-radioactive) iodine, blocking radioiodide uptake into the gland, is essential in these subpopulations. However, a quantitative estimation of the protection conferred to the maternal and fetal thyroids in the different stages of pregnancy is difficult. We departed from an established biokinetic model for radioiodine in pregnancy using first-order kinetics. As the uptake of iodide into the thyroid and several other tissues is mediated by a saturable active transport, we integrated an uptake mechanism described by a Michaelis–Menten kinetic. This permits simulating the competition between stable and radioactive iodide at the membrane carrier site, one of the protective mechanisms. The Wollf–Chaikoff effect, as the other protective mechanism, was simulated by adding a total net uptake block for iodide into the thyroid, becoming active when the gland is saturated with iodine. The model’s validity was confirmed by comparing predicted values with results from other models and sparse empirical data. According to our model, in the case of radioiodine exposure without thyroid blocking, the thyroid equivalent dose in the maternal gland increases about 45% within the first weeks of pregnancy to remain in the same range until term. Beginning in the 12th pregnancy week, the equivalent dose in the fetal thyroid disproportionately increases over time and amounts to three times the dose of the maternal gland at term. The maternal and fetal glands’ protection increases concomitantly with the amount of stable iodine administered to the mother simultaneously with acute radioiodine exposure. The dose–effect curves reflecting the combined thyroidal protection by the competition at the membrane carrier site and the Wolff–Chaikoff effect in the mother are characterized by a mean effective dose (ED₅₀) of roughly 1.5 mg all over pregnancy. In the case of the fetal thyroid, the mean effective doses for thyroid blocking, taking into account only the competition at the carrier site are numerically lower than in the mother. Taking into account additionally the Wolff–Chaikoff effect, the dose–effect curves for thyroidal protection in the fetus show a shift to the left over time, with a mean effective dose of 12.9 mg in the 12th week of pregnancy decreasing to 0.5 mg at term. In any case, according to our model, the usually recommended dose of 100 mg stable iodine given at the time of acute radioiodine exposure confers a very high level of thyroidal protection to the maternal and fetal glands over pregnancy. For ethical reasons, the possibilities of experimental studies on thyroid blocking in pregnant women are extremely limited. Furthermore, results from animal studies are associated with the uncertainties related to the translation of the data to humans. Thus model-based simulations may be a valuable tool for better insight into the efficacy of thyroidal protection and improve preparedness planning for uncommon nuclear or radiological emergencies.

Is there a role for diagnostic scans in the management of intermediate-risk thyroid cancer?

Radioiodine (RAI) is selectively recommended for intermediate-risk differentiated thyroid carcinomas (DTC). The information gleaned from pretherapy stimulated thyroglobulin levels (sTg) and diagnostic 131I whole-body scans (DxWBS) to guide therapy remains controversial. The present study aimed at evaluating the impact of preablation sTg and DxWBS in the management of intermediate-risk DTC. A retrospective analysis of 301 intermediate-risk DTC patients submitted to total thyroidectomy and RAI therapy was performed. Pretherapy sTg and DxWBS and post-therapy WBS (RxWBS) findings were analyzed and compared to outcomes. Fifty-two patients (17.3%) had metastases diagnosed by DxWBS and/or RxWBS. The DxWBS identified 10.6% of patients with functioning metastases, including unexpected distant metastases. If combined with SPECT-CT, DxWBS detected RAI-avid metastases more frequently, particularly lymph node metastases (13.1% vs 4.2% planar WBS, P = 0.015). The DxWBS findings modified patient management in 8.3%. A pretherapy sTg <1 ng/mL was associated with a low false-negative rate for the presence of metastases (5.2%), and its performance in excluding metastasis was improved by a negative DxWBS (2.7% of patients with both negative exams had metastases in RxWBS). A sTg <1 ng/mL predicted statistically significant lower rates of recurrent/persistent disease and biochemical/structural incomplete responses. In conclusion, preablation sTg and DxWBS contribute to the detection of unknown or persistent metastatic disease in intermediate-risk DTC patients. A sTg <1 ng/mL in combination with a negative DxWBS is highly suggestive of the absence of remaining malignant disease, and one may consider deferring RAI ablation if both exams are negative. A stunning effect is rarely observed and it does not impair proper treatment of metastases.

Personalized Dosimetry in the Context of Radioiodine Therapy for Differentiated Thyroid Cancer

The most frequent thyroid cancer is Differentiated Thyroid Cancer (DTC) representing more than 95% of cases. A suitable choice for the treatment of DTC is the systemic administration of 131-sodium or potassium iodide. It is an effective tool used for the irradiation of thyroid remnants, microscopic DTC, other nonresectable or incompletely resectable DTC, or all the cited purposes. Dosimetry represents a valid tool that permits a tailored therapy to be obtained, sparing healthy tissue and so minimizing potential damages to at-risk organs. Absorbed dose represents a reliable indicator of biological response due to its correlation to tissue irradiation effects. The present paper aims to focus attention on iodine therapy for DTC treatment and has developed due to the urgent need for standardization in procedures, since no unique approaches are available. This review aims to summarize new proposals for a dosimetry-based therapy and so explore new alternatives that could provide the possibility to achieve more tailored therapies, minimizing the possible side effects of radioiodine therapy for Differentiated Thyroid Cancer.

Comparing High and Low-Dose Radio-Iodine Therapy in Thyroid Remnant Ablation Among Intermediate and Low-Risk Papillary Thyroid Carcinoma Patients-Single Centre Experience

The role of Iodine-131 therapy is well established as an adjuvant therapy and for thyroid remnant ablation in differentiated thyroid cancer (DTC); however controversy still exists regarding its appropriate dose. Purpose of this study was to compare the effectiveness of low-dose and high-dose Iodine-131 ablation therapies in low- and intermediate-risk PTC patients. Eighty-four patients were divided equally into Group I: Ablated with high dose of Iodine-131 and Group II: Ablated with low dose of Iodine-131. Iodine-131 WBS, serum TG levels and USG neck of all patients were performed at first presentation, 6 months, 1 year, and 2 years follow up. Results are as follows: Group I: 64%, 72%, and 76% intermediate-risk patients were disease free at the follow up intervals of 6 months, 1 year, and 2 years, respectively. Similarly 70%, 82%, and 82% low-risk patients were disease free at above mentioned intervals. Group II: 56%, 60%, and 64% were disease free among intermediate-risk patients while percentage of disease free low-risk patients was 70%, 76%, and 76% at follow up intervals. Low dose of radioactive Iodine-131 was found as effective as high dose in thyroid remnant ablation of PTC patients.

Radioiodine Remnant Ablation for Differentiated Thyroid Cancer: A Systematic Review and Meta-analysis

Importance

Postoperative radioactive iodine (RAI) remnant ablation for differentiated thyroid cancer (DTC) facilitates the early detection of recurrence and represents an adjuvant therapy that targets persistent microscopic disease. The optimal activity of RAI in low- and intermediate-risk DTC remains controversial.

Objective

To evaluate the long-term cure rate of different RAI activities in low- and intermediate-risk DTC. Secondary outcomes included successful remnant ablation, adverse effects, and hospital length of stay.

Data Source

A systematic search of the databases PubMed, Cochrane Collaboration, Embase, Scopus, and Web of Science was performed to identify randomized clinical trials (RCTs) and observational studies that compared long-term outcomes (>12 months) for American Thyroid Association-classified low- and intermediate-risk DTC based on receipt of either low-activity or high-activity RAI postoperatively.

Study Selection

All RCTs or observational studies evaluating patients with low- and intermediate-risk DTC who were treated initially with total/near-total thyroidectomy, followed by remnant RAI ablation with either low or high activities. Eligible studies had to present odds ratio, relative risk (RR), or hazard ratio estimates (with 95% CIs), standard errors, or the number of events necessary to calculate these for the outcome of interest rate.

Data Extraction

Two investigators reviewed the literature in accordance with Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Dichotomous variables were pooled as risk ratios and continuous data as weighted-mean differences. Quality assessment of the included studies was performed using the Newcastle-Ottawa and Jadad scales.

Main Outcomes and Measures

Disease recurrence was the primary outcome. Secondary outcomes included successful ablation, adverse effects, and length of stay.

Results

Ten studies that included 3821 patients met inclusion criteria, including 6 RCTs and 4 observational studies. There was no difference in long-term cure recurrence rates (RR, 0.88; 95% CI, 0.62-1.27, P = .50) or successful remnant ablation (RR, 0.95; 95% CI, 0.87-1.03; P = .20) between low-activity and high-activity RAI.

Conclusions and Relevance

In this systematic review and meta-analysis, low-activity RAI was comparable with high-activity RAI regarding successful ablation and recurrence rates. This suggests that low-activity RAI is preferable to high-activity in low- and intermediate-risk DTC because of its similar efficacy but reduced morbidity.

Trial Registration

PROSPERO Identifier: CRD42020166780.

The role of Hashimoto thyroiditis in predicting radioiodine ablation efficacy and prognosis of low to intermediate risk differentiated thyroid cancer

OBJECTIVE

The baseline treatment of differentiated thyroid cancer (DTC) consists of thyroidectomy followed by postoperative risk-adapted radioiodine therapy (RAIT) when indicated. The choice of most appropriate RAI activities to administer with the aim to reach an efficient remnant ablation and reduce the risk of recurrence is yet an open issue and the detection of basal factors that may predict treatment response seems fundamental. The aim of this study was to investigate the potential role of Hashimoto thyroiditis (HT) in predicting 1-year and 5-year treatment response after RAIT and prognosis.

METHODS

We retrospectively included 314 consecutive patients (174 low-risk and 140 intermediate-risk) who received thyroidectomy plus RAIT. One-year and 5-year disease status was evaluated according to 2015 ATA categories response based upon biochemical and structural findings.

RESULTS

HT was reported histopathologically in 120 patients (38%). DTC patients with concomitant HT received a higher number of RAITs and cumulative RAI activities. Initial RAIT reached an excellent response in 63% after one year and 84% after 5 years. The rate of excellent response one year and 5-year after first RAIT was significantly lower in HT groups, compared to not HT (p < 0.001). Instead, HT did not have a prognostic role considering PFS and OS; while stimulate thyroglobulin (sTg) at ablation was significantly related to survival.

CONCLUSIONS

HT may affect the efficacy of RAIT in low to intermediate risk DTC, particularly reducing the successful rate of excellent response after RAIT. Instead, HT did not have a prognostic impact such as stimulated sTg.

Setting up a quantitative SPECT imaging network for a European multi-centre dosimetry study of radioiodine treatment for thyroid cancer as part of the MEDIRAD project

Background

Differentiated thyroid cancer has been treated with radioiodine for almost 80 years, although controversial questions regarding radiation-related risks and the optimisation of treatment regimens remain unresolved. Multi-centre clinical studies are required to ensure recruitment of sufficient patients to achieve the statistical significance required to address these issues. Optimisation and standardisation of data acquisition and processing are necessary to ensure quantitative imaging and patient-specific dosimetry.

Material and methods

A European network of centres able to perform standardised quantitative imaging of radioiodine therapy of thyroid cancer patients was set-up within the EU consortium MEDIRAD. This network will support a concurrent series of clinical studies to determine accurately absorbed doses for thyroid cancer patients treated with radioiodine. Five SPECT(/CT) systems at four European centres were characterised with respect to their system volume sensitivity, recovery coefficients and dead time.

Results

System volume sensitivities of the Siemens Intevo systems (crystal thickness 3/8″) ranged from 62.1 to 73.5 cps/MBq. For a GE Discovery 670 (crystal thickness 5/8″) a system volume sensitivity of 92.2 cps/MBq was measured. Recovery coefficients measured on three Siemens Intevo systems show good agreement. For volumes larger than 10 ml, the maximum observed difference between recovery coefficients was found to be ± 0.02. Furthermore, dead-time coefficients measured on two Siemens Intevo systems agreed well with previously published dead-time values.

Conclusions

Results presented here provide additional support for the proposal to use global calibration parameters for cameras of the same make and model. This could potentially facilitate the extension of the imaging network for further dosimetry-based studies.

Can we safely reduce the administration of 131-iodine in patients with differentiated thyroid cancer? - experience of the Brugmann hospital in Brussels

Background

131-iodine (¹³¹I) administration after surgery remains a standard practice in differentiated thyroid cancer (DTC). In 2014, the American Thyroid Association presented new guidelines for the staging and management of DTC, including no systematic ¹³¹I in patients at low-risk of recurrence and a reduced ¹³¹I activity in intermediate risk.The present study aims at evaluating the rate of response to treatment following this new therapeutic management compared to our previous treatment strategy in patients with DTC of different risks of recurrence.

Methods

Patients treated and followed up for DTC according to the 2014-ATA guidelines (Group 2) were compared to those treated between 2007 and 2014 (Group 1) in terms of general characteristics, risk of recurrence (based on the 2015-ATA recommendations), preparation to ¹³¹I administration, cumulative administered ¹³¹I activity and response to treatment.

Results

In total, 136 patients were included: 78 in Group 1 and 58 in Group 2. The two groups were not statistically different in terms of clinical characteristics nor risk stratification: 42.3% in Group 1 and 31% in Group 2 were classified as low risk, 38.5 and 48.3% as intermediate risk and 19.2 and 20.7% as high risk (P = 0.38). Two patients (one in each group) with distant metastases were excluded from the analysis.Preparation to ¹³¹I administration consisted in rhTSH stimulation in 23.4% of the patients in Group 1 and 100% in Group 2 (p < 0.001).¹³¹I was administered to 46/77 patients (59.7%) in Group 1 (5 at low risk of recurrence) and 38/57 patients (66.7%) in Group 2 (0 with a low risk). Among the patients treated by ¹³¹I, median cumulative activity was significantly higher in Group 1 (3.70GBq [100 mCi] range 1.11-11.1 GBq [30-300 mCi]) than in Group 2 (1.11 GBq [30 mCi], range 1.11-7.4 GBq [30-200 mCi], P < 0.001). Complete response was found in 90.9% in Group 1 vs. 96.5% in Group 2 (P = 0.20).

Conclusions

Using the 2015-ATA evidence-based guidelines for the management of DTC, meaning no ¹³¹I administration in low-risk patients, a low activity in intermediate and even high risk patients, and a systematic use of rhTSH stimulation before ¹³¹I therapy allowed us to reduce significantly the median administered ¹³¹I activity, with a similar rate of complete therapeutic response.

The revised clinical practice guidelines on the management of thyroid tumors by the Japan Associations of Endocrine Surgeons: Core questions and recommendations for treatments of thyroid cancer

The Japan Associations of Endocrine Surgeons has developed the revised version of the Clinical Practice Guidelines for Thyroid Tumors. This article describes the guidelines translated into English for the 35 clinical questions relevant to the therapeutic management of thyroid cancers. The objective of the guidelines is to improve health-related outcomes in patients with thyroid tumors by enabling users to make their practice evidence-based and by minimizing any variations in clinical practice due to gaps in evidential knowledge among physicians. The guidelines give representative flow-charts on the management of papillary, follicular, medullary, and anaplastic thyroid carcinoma, along with recommendations for clinical questions by presenting evidence on the relevant outcomes including benefits, risks, and health conditions from patients' perspective. Therapeutic actions were recommended or not recommended either strongly (◎◎◎ or XXX) based on good evidence (😊)/good expert consensus (+++), or weakly (◎, ◎◎ or X, XX) based on poor evidence (😣)/poor expert consensus (+ or ++). Only 10 of the 51 recommendations given in the guidelines were supported by good evidence, whereas 35 were supported by good expert consensus. While implementing the current guidelines would be of help to achieve the objective, we need further clinical research to make our shared decision making to be more evidence-based.

Longer-term recurrence rate after low versus high dose radioiodine ablation for differentiated thyroid Cancer in low and intermediate risk patients: a meta-analysis

Background

Regarding the longer-term recurrence rate the optimal activity for the remnant thyroid ablation in patients with differentiated thyroid cancer (DTC) is discussed controversially. For the short-term ablation success rate up to 12 months there are already several meta-analyses. In this study we performed the first meta-analysis regarding the longer-term recurrence rate after radioactive 131-I administration.

Methods

We conducted an electronic search using PubMed/MEDLINE, EMBASE and the Cochrane Library. All randomized controlled trials (RCTs) assessed the recurrence rate after radioactive iodine ablation in patients with DTC, with a follow-up of at least two years were selected. Statistics were performed by using Review Manager version 5.3 and Stata software.

Results

Four RCTs were included in the study, involving 1501 patients. There was no indication for heterogeneity (I² = 0%) and publication bias. The recurrence rate among patients who had a low dose 131-iodine ablation was not higher than for a high dose activity (odds ratio (OR) 0.93 [95% confidence interval (CI) 0.53–1.63]; P = 0.79). The mean follow-up time was between 4.25 and 10 years. The subgroup analysis regarding the TSH stimulated thyroglobulin values (< 10 ng/mL versus < 2 ng/mL versus ≤1 ng/mL) showed no influence on recurrence rate.

Conclusions

For the first time we showed that the longer-term, at least 2-year follow-up, recurrence rate among patients who had 131-iodine ablation with 1.1 GBq was not higher than with 3.7 GBq.

Impact on testicular function of a single ablative activity of 3.7 GBq radioactive iodine for differentiated thyroid carcinoma

STUDY QUESTION

What are the consequences of radioactive iodine (RAI) therapy for testicular function?

SUMMARY ANSWER

A single activity of 3.7 GBq RAI for differentiated thyroid carcinoma (DTC) treatment in young men transiently altered Sertoli cell function and induced sperm chromosomal abnormalities.

WHAT IS KNOWN ALREADY

Few studies, mainly retrospective, have reported the potential impacts of RAI on endocrine and exocrine testicular function.

STUDY DESIGN, SIZE, DURATION

A longitudinal prospective multi-center study on testicular function performed in DTC patients before a single 131I ablative activity of 3.7 GBq (V0) and at 3 months (V3) and 13 months (V13) after treatment.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Forty male patients, aged 18-55 years, with DTC participated. Hormonal analysis included FSH, LH, testosterone and inhibin B serum levels at V0, V3 and V13. Furthermore, sperm parameters, DNA fragmentation and sperm chromosomal abnormalities were evaluated at each time points. The differences in all parameters, between V0-V3, V0-V13 and V3-V13, were analyzed, using a Wilcoxon test.

MAIN RESULTS AND THE ROLE OF CHANCE

Prior to RAI administration, all patients had normal gonadal function. At V3, a statistically significant increase in FSH levels and a decrease in inhibin B levels were observed and sperm concentration, as well as the percentage of morphologically normal spermatozoa, were significantly decreased (P < 0.0001). These modifications were transient as both sperm concentration and normal morphology rate returned to baseline values at V13. However, at this later time point, FSH and inhibin B levels were still impacted by RAI administration but remained in the normal range. Although no DNA fragmentation was observed at V3 nor V13, our study revealed a statistically significant increase in the number of sperm chromosomal abnormalities both at V3 (P < 0.001) and V13 (P = 0.01).

LIMITATIONS, REASONS FOR CAUTION

Among the 40 patients included in the study, only 24 had all the parameters available at all visits.

WIDER IMPLICATIONS OF THE FINDINGS

Prospective studies with longer term follow up would be helpful to determine whether the chromosome abnormalities persist. These studies would be required before sperm banking should be suggested for all patients. However, sperm preservation for DTC patients who require cumulative radioiodine activities higher than 3.7 GBq should be proposed.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the Programme Hospitalier de Recherche Clinique, AP-HP (No. P040419). The authors report no conflict of interest in this work.

TRIAL REGISTRATION NUMBER

NCT01150318.

Efficacy of low radioiodine activity versus intermediate-high activity in the ablation of low-risk differentiated thyroid cancer

PURPOSE

The aim of our study was to compare the efficacy of thyroid remnant ablation using low (1.1 GBq) and intermediate-high radioiodine (RAI) activity (1.85-3.7 GBq) in low-risk differentiated thyroid carcinoma (DTC) and to evaluate the staging role of the whole body scan (WBS) in detection extrathyroidal disease.

MATERIALS AND METHODS

We retrospectively included 277 patients who underwent total thyroidectomy and RAI for low-risk DTC and divided them in two groups according to RAI activity at ablation: group 1 (n = 174) treated with low activity (1.1 GBq), and group 2 (n = 103) with intermediate-high activity (1.85-3.7 GBq). To evaluate the successful ablation rate, the WBS 1 year after RAI was visually interpreted using a three-point scale: score 0 in case of absence of visible RAI uptake in thyroid bed; score 1 in presence of faint uptake in the thyroid bed; and score 2 in case of significant RAI uptake in thyroid bed.

RESULTS

The success ablation rate was significantly higher in group 2 than group 1 (p < 0.001) with the presence of a positive WBS (score 1-2) in 65% low-activity group and 33% in intermediate-high group. Considering response to therapy categories, excellent response rate was significantly higher in group 2 (p = 0.020), while indeterminate response was higher in group 1 (p value = 0.005). Post RAI imaging revealed extrathyroidal uptake in 27 cases: 17 laterocervical nodal and 10 distant metastases. In both groups similar detection rate of nodal and distant metastases were recognized without any statistical difference.

CONCLUSIONS

The ablation rate with intermediate-high RAI activity (1.85-3.7 GBq) was better than with a low activity (1.1 GBq). First WBS may help to recognize nodal and distant metastases in about 10% of cases changing clinical stage and subsequent management.

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.

Clinical outcomes of patients with T4 or N1b well-differentiated thyroid cancer after different strategies of adjuvant radioiodine therapy

We aimed to determine whether recombinant human thyrotropin (rhTSH) plus 3.7 GBq could replace thyroid hormone withdrawal (THW) plus 5.55 GBq for adjuvant radioactive iodine (RAI) therapy in differentiated thyroid cancer (DTC) patients with T4 or N1b disease. This study was a retrospective study comparing ablation success rate, response to initial therapy, and recurrence-free survival (RFS) of patients with rhTSH plus 3.7 GBq versus those with THW plus 5.55 GBq in 253 DTC patients with T4 or N1b disease. There were no differences in the TSH-stimulated thyroglobulin level, rate of incomplete response after initial treatment, or the RFS between the two treatment strategies. However, thyroid bed uptake on follow-up diagnostic RAI whole-body scanning (WBS) was more frequently observed in the group treated with rhTSH plus 3.7 GBq than in the group with THW plus 5.55 GBq. Adjuvant RAI therapy with rhTSH plus 3.7 GBq had comparable results in the absence of persistent tumor, compared with that with THW plus 5.55 GBq. Although thyroid bed uptake was more frequently observed, rhTSH plus 3.7 GBq may be used instead of THW plus 5.55 GBq for adjuvant RAI therapy in patients with T4 or N1b disease.

Differentiated thyroid cancer theranostics: radioiodine and beyond

The term theranostics is the combination of a diagnostic tool that helps to define the right therapeutic tool for specific disease. It signifies the "we know which sites require treatment (diagnostic scan) and confirm that those sites have been treated (post-therapy scan)" demonstrating the achievable tumor dose concept. This term was first used by John Funkhouser at the beginning of the 90s, at the same time the concept of personalized medicine appeared. In nuclear medicine, theranostics is easy to apply and understand because of an easy switch from diagnosis to therapy with the same vector. It helps in maximizing tumor dose and sparing normal tissue with high specific and rapid uptake in metastasis. The oldest application of this concept is radioactive iodine I-131 (RAI). The first treatment based on the theranostic concept was performed on thyroid cancer patients with RAI in 1946. From then on management of differentiated thyroid cancer (DTC) has evolved on the multimodality concept. We now use the term "our" patient instead of "my" patient to signify this. However, the initial surgical management followed by RAI as per the theranostics has remained the mainstay in achieving a cure in most of DTC patients. The normal thyroid cells metabolise iodine, the principle of which is utilized in imaging of the thyroid gland with isotopes of iodine. RAI treatment of DTC is based on the principle of sodium iodide symporter (NIS) expressing thyroid cells with DTC cells having the ability of trapping circulating RAI successfully helping in treatment of residual and metastatic disease. NIS is usually negative in poorly differentiated cells and is inversely proportional to Glucose transporter receptor Type 1 expression. Both positive and negative NIS are the key components of the theranostic approach in treatment of DTC. Presence or absence of NIS is documented by either whole body iodine scintigraphy (WBS) or 2-deoxy-2(18F) fludeoxyglucose (FDG) positron emission tomography computed tomography (PET-CT). Currently, single photon emission CT and CT (SPECT-CT) has significantly improved the precision and sensitivity of whole body iodine scintigraphy with its capability of accurate localization of disease foci whether iodine avid or non-avid. This has helped in a more personalized approach in treatment. This review will give an overview of the role of NIS in the theranostic approach to management with RAI, its current status and also the molecular approach to treatment in RAI refractory disease.

Clinical outcomes and associated factors of radioiodine-131 treatment in differentiated thyroid cancer with cervical lymph node metastasis

Cervical lymph node metastasis (CLNM) is common in differentiated thyroid cancer (DTC). Radioiodine-131 (¹³¹I) treatment is recommended for the removal of residual thyroid tissue following thyroidectomy. To date, the effect of ¹³¹I therapy on the outcomes of patients with DTC with CLNM is unclear. The aim of the present study was to evaluate the final outcome of patients with DTC with CLNM according to ¹³¹I administration, and to analyze the factors that may affect clinical outcomes. A total of 357 patients with DTC with CLNM were recruited and divided into three groups: Those who received 2, 3 or 4 doses of ¹³¹I therapy, respectively. Successful ablation was defined as levels of stimulated serum thyroglobulin <2 ng/ml in the absence of CLNM. The rates of successful ablation were 80.35 (229/285), 76.36 (42/55) and 70.59% (12/17) for patients who received 2, 3 and 4 doses, respectively. The patients with DTC with CLNM who were <45 years old, with tumor sizes <2 cm, solitary nodules and TNM stage I-II disease exhibited significantly higher rates of successful ablation compared with the patients who were ≥45 years old, with tumor size ≥2 cm, multiple nodules and stage III-IV disease. Multivariate analyses revealed that tumor size, number of nodules and TNM stage were independent risk factors associated with successful ablation in patients with DTC with CLNM who received 2 doses of ¹³¹I therapy. ¹³¹I administration is a useful therapy to eradicate cervical lymph node metastasis in patients with DTC, and may be preferentially indicated in patients with DTC with CLNM who are aged <45 years, with tumor sizes <2 cm, solitary nodules and lower TNM stages, in order to control and prevent recurrence and/or metastases.

One-step synthesis of Ag2O@Mg(OH)2 nanocomposite as an efficient scavenger for iodine and uranium

Ag₂O nanoparticles anchored on the Mg(OH)₂ nanoplates (Ag₂O@Mg(OH)₂) were successfully prepared by a facile one-step method, which combined the Mg(OH)₂ formation with Ag₂O deposition. The synthesized products were characterized by a wide range of techniques including powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and nitrogen physisorption analysis. It was found that Ag₂O nanoparticles anchored on the Mg(OH)₂ nanoplates show good dispersion and less aggregation relative to the single Ag₂O nanoaggregates. In addition, iodide (I^-) removal by the Ag₂O@Mg(OH)₂ nanocomposite was studied systematically. Batch experiments reveal that the nanocomposite exhibits extremely high I^- removal rate (<10min), and I^- removal capacity is barely affected by the concurrent anions, such as Cl^-, SO₄^2-, CO₃^2- and NO₃^-. Furthermore, I^- and UO₂²⁺ could be simultaneously removed by the nanocomposite with high efficiency. Due to the simple synthetic procedure, the excellent removal performances for iodine and uranium, and the easy separation from water, the Ag₂O@Mg(OH)₂ nanocomposite has real potential for application in radioactive wastewater treatment, especially during episodic environmental crisis.

Low versus high radioiodine activity for ablation of the thyroid remnant after thyroidectomy in Han Chinese with low-risk differentiated thyroid cancer

AIM

The aim of this study was to compare the efficacy and adverse effects of radioiodine (¹³¹I) therapy between two groups of patients with low-risk differentiated thyroid cancer (DTC) who received 30 mCi or 100 mCi radioiodine for ablation of the thyroid remnant after total thyroidectomy.

METHODS

The study cohort was 173 patients, 85 of whom were given 30 mCi of radioiodine and the others were given 100 mCi of radioiodine. Follow-up involved neck ultrasonography, measurement of serum levels of thyroglobulin and whole-body scans to evaluate the response of radioiodine treatment. All patients were assessed for adverse effects.

RESULTS

Of the 173 patients, 170 (98.3%) patients finally achieved successful ablation. The prevalence of successful ablation was 77.6% in the low-dose group versus 71.5% in the high-dose group after the first dose administration (P=0.36), 79% in the low-dose group versus 88% in the high-dose group after the second dose administration (P=0.416), and 97.6% in the low-dose group versus 98.9% in the high-dose group after the final ablation (P=0.54). We found no significant differences between the two groups. No patient had an adverse effect with a severity grade ⩾2 and the prevalence of adverse effects in the high-dose group was higher than that in the low-dose group, especially for nausea, neck pain, and sore throat.

CONCLUSION

These data suggest that a low dose of radioiodine is as effective as a high dose of radioiodine for ablation of the thyroid remnant after total thyroidectomy for low-risk DTC. Moreover, low-dose radioiodine therapy is associated with a lower prevalence of adverse events.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

I-131 for Remnant Ablation in Differentiated Thyroid Cancer After Thyroidectomy: A Meta-Analysis of Randomized Controlled Evidence

Background

The aim of this study was to compare the success rate of various levels of I-131 activity for use in remnant ablation in low-risk differentiated thyroid cancer.

Material/Methods

We identified eligible studies in 5 electronic databases up to December 2014 and the reference lists of original studies and review articles were hand searched for additional articles on this topic. Summary relative risks with their 95% confidence intervals were calculated with a random-effects model. Heterogeneity was assessed using I² statistics.

Results

Fourteen randomized clinical trials met the eligibility criteria. The data suggest that the pooled successful ablation rate is 5% lower (95% CI, 1–9% lower) when using 30 mCi compared with 100 mCi (test for heterogeneity, p=0.468, I²=0.0%). In stratified analysis, ablation success rates using 30 mCi are similar to 100 mCi in Asia (SRRs=0.91; 95%CI=0.72–1.14). However, the results favor 100 mCi in Europe (SRRs=0.95; 95%CI=0.91–0.99). Ablation success rates using 30 mCi are similar to 100 mCi in patients who underwent TT/NTT (total thyroidectomy/near total thyroidectomy) (SRRs=0.96; 95%CI=0.92–1.00) and TT/STT (SRRs=0.98; 95%CI=0.73–1.31). However, the result favor 100 mCi in patients who underwent ST/HT (subtotal thyroidectomy/ hemithyroidectomy) (SRRs=0.80; 95%CI=0.65–0.99). There was no publication bias in the present meta-analysis.

Conclusions

High radioiodine activity is better than low activity in terms of successful ablation rate in low-risk differentiated thyroid cancer, but the advantage of high activity seems to only exist in patients who underwent hemithyroidectomy/subtotal thyroidectomy, but not lymph node involvement, preparation before ablation, and definition of successful ablation.

Implication of different clinical and pathological variables in patients with differentiated thyroid cancer on successful ablation for 3700 MBq (131)I: a single Egyptian institutional experience over 14 years

OBJECTIVE

Is to investigate possible factors predicting success of ablation for 3700 MBq radioactive iodine 131 in patients with differentiated thyroid cancer (DTC) following near total thyroidectomy.

METHODS

This retrospective study enrolled 272 patients between 2000 and 2014. The success or failure of ablation was assessed 6 months after given the dose and our criteria for complete successful remnant ablation defined as: Negative (131)I whole body scan with no residual functioning thyroid tissue or distant functioning metastases and stimulated thyroglobulin (Tg) level less than 2 ng/ml. Different clinical and pathological factors, such as age, gender, tumor histology, grade and variants, size of primary malignant lesion, stage, and risk assessment according to the American (ATA) and European Thyroid Association (ETA) guidelines, associated pathology, tumor mutifocality, lymph node (LN) metastases and their number, invasiveness of the tumor (capsular invasion of the nodule, extra-thyroidal extension, and vascular invasion), baseline stimulated Tg level, and pre-ablative diagnostic scan were assessed.

RESULTS

There were 185 successful ablations (68 %). The baseline-stimulated Tg measured before the ablation was the only independent predictor of ablation success in multivariate analysis (P < 0.0001) with odds ratio (OR) of 2.64 (95 % CI: 1.54-4.54) and the optimal cutoff for this was 3.8 ng/mL. On the univariate analysis, LN metastases was predictor of ablation failure (P value = 0.03).

CONCLUSION

Baseline-stimulated Tg level is clinically important and had a significant predictive value for successful ablation; therefore, higher pre-ablation Tg should potentially be incorporated in the decision making for (131)I dosage or other treatment. In accordance with other studies, this is also applicable to cervical lymph nodal involvement and thyroid capsule invasion.

Different Radioiodine Dose for Remnant Thyroid Ablation in Patients With Differentiated Thyroid Cancer: A Meta-analysis

OBJECTIVE

Remnant thyroid ablation is crucial in the management of patients with differentiated thyroid cancer. However, the optimal dose of radioactive I for ablation is still controversial. This study aimed to compare the success rate of different activities of I for postoperative remnant ablation in randomized controlled trials (RCTs) and to determine the optimal dose.

PATIENTS AND METHODS

Sources were retrieved from the Cochrane Library, Medline, Embase, Scopus, and Google Scholar until March 2014. All RCTs that assessed the efficacy of different doses of I for ablation were selected. After data extraction, statistics were performed by Review Manager 5.2 software.

RESULTS

Seventeen RCTs were considered eligible, involving 3737 patients. The overall methodological quality of the studies was good. The rate of successful remnant ablation of low versus moderate I activities (risk ratio [RR], 0.89; 95% confidence interval [CI], 0.80-1.00; P = 0.06) and moderate versus high I activities (RR, 0.94; 95% CI, 0.89-1.00; P = 0.05) showed no significant differences. However, high I activities had 11% higher successful ablation rate than low activities with an RR of 0.89 (95% CI, 0.81-0.97; P = 0.008), which was significant.

CONCLUSIONS

We summarized all available randomized evidence to demonstrate that high dose of I was significantly better than low dose to achieve successful remnant thyroid ablation.

Recommendations for post-surgical thyroid ablation in differentiated thyroid cancer: a 2015 position statement of the Italian Society of Endocrinology

Post-surgical ablation of thyroid remnant with radioactive iodine (RAI) in differentiated thyroid cancer (DTC) is aimed to destroy any thyroid remnant in the thyroid bed (remnant ablation) and any microscopic foci of cancer cells eventually present within the thyroid remnant (adjuvant therapy). The present text is an attempt to offer practice guidelines for the indication of thyroid ablation and the preparation of DTC patients considering the latest achievement in the field and the changing epidemiology of DTC observed in the last 10 years.

METHODOLOGY

The executive committee of the Italian Society of Endocrinology appointed a task force of thyroid cancer expert including Nuclear Medicine Physicians and Endocrinologists to provide a consensus on the post-surgical ablation in thyroid cancer patients. The task force had no conflict of interest and had no commercial support. A number of specific topics were selected and the members selected relevant papers by searching in the Pubmed for articles published from 2000 to January 2015. Selected studies were categorized by level of evidence, and the recommendations were graded according to the level of evidence as high (A), moderate (B), or low (C).

Radioiodine Remnant Ablation: A Critical Review

Radioiodine remnant ablation (RRA) is considered a safe and effective method for eliminating residual thyroid tissue, as well as microscopic disease if at all present in thyroid bed following thyroidectomy. The rationale of RRA is that in the absence of thyroid tissue, serum thyroglobulin (Tg) measurement can be used as an excellent tumor marker. Other considerations are like the presence of significant remnant thyroid tissue makes detection and treatment of nodal or distant metastases difficult. Rarely, microscopic disease in the thyroid bed if not ablated, in the future, could be a source of anaplastic transformation. On the other hand, microscopic tumor emboli in distant sites could be the cause of distant metastasis too. The ablation of remnant tissue would in all probability eliminate these theoretical risks. It may be noted that all these are unproven contentious issues except postablation serum Tg estimation that could be a good tumor marker for detecting early biochemical recurrence in long-term follow-up strategy. Radioactive iodine is administered as a form of “adjuvant therapy” for remnant ablation. There have been several reports with regard to the administered dose for remnant ablation. The first report of a prospective randomized clinical trial was published from India by a prospective randomized study conducted at the All India Institute of Medical Sciences, New Delhi in the year 1996. The study reported that increasing the empirical ¹³¹I initial dose to more than 50 mCi results in plateauing of the dose-response curve and thus, conventional high-dose remnant ablation needs critical evaluation. Recently, two important studies were published: One from French group and the other from UK on a similar line. Interestingly, all three studies conducted in three different geographical regions of the world showed exactly similar conclusion. The new era of low-dose remnant ablation has taken a firm scientific footing across the continents.

Clinical Outcome of Remnant Thyroid Ablation with Low Dose Radioiodine in Korean Patients with Low to Intermediate-risk Thyroid Cancer

Radioiodine activity required for remnant thyroid ablation is of great concern, to avoid unnecessary exposure to radiation and minimize adverse effects. We investigated clinical outcomes of remnant thyroid ablation with a low radioiodine activity in Korean patients with low to intermediate-risk thyroid cancer. For remnant thyroid ablation, 176 patients received radioiodine of 1.1 GBq, under a standard thyroid hormone withdrawal and a low iodine diet protocol. Serum levels of thyroid stimulating hormone stimulated thyroglobulin (off-Tg) and thyroglobulin-antibody (Tg-Ab), and a post-therapy whole body scan (RxWBS) were evaluated. Completion of remnant ablation was considered when there was no visible uptake on RxWBS and undetectable off-Tg (<1.0 ng/mL). Various factors including age, off-Tg, and histopathology were analyzed to predict ablation success rates. Of 176 patients, 68.8% (n = 121) who achieved successful remnant ablation were classified into Group A, and the remaining 55 were classified into Group B. Group A presented with significantly lower off-Tg at the first radioiodine administration (pre-ablative Tg) than those of Group B (1.2 ± 2.3 ng/mL vs. 6.2 ± 15.2 ng/mL, P = 0.027). Pre-ablative Tg was the only significant factor related with ablation success rates. Diagnostic performances of pre-ablative Tg < 10.0 ng/mL were sensitivity of 99.1%, specificity of 14.0%, positive predictive value of 71.1%, and negative predictive value of 87.5%, respectively. Single administration of low radioiodine activity could be sufficient for remnant thyroid ablation in patients with low to intermediate-risk thyroid cancer. Pre-ablative Tg with cutoff value of 10.0 ng/mL is a promising factor to predict successful remnant ablation.

Recombinant TSH stimulated remnant ablation therapy in thyroid cancer: the success rate depends on the definition of ablation success--an observational study

INTRODUCTION

Patients with differentiated thyroid cancer (DTC) are treated with (near)-total thyroidectomy followed by remnant ablation. Optimal radioiodine-131 (131I) uptake is achieved by withholding thyroid hormone (THW), pretreatment with recombinant human Thyrotropin Stimulating Hormone (rhTSH) is an alternative. Six randomized trials have been published comparing THW and rhTSH, however comparison is difficult because an uniform definition of ablation success is lacking. Using a strict definition, we performed an observational study aiming to determine the efficacy of rhTSH as preparation for remnant ablation.

PATIENTS AND METHODS

Adult DTC patients with, tumor stage T1b to T3, Nx, N0 and N1, M0 were included in a prospective multicenter observational study with a fully sequential design, using a stopping rule. All patients received remnant ablation with 131I using rhTSH. Ablation success was defined as no visible uptake in the original thyroid bed on a rhTSH stimulated 150 MBq 131I whole body scan (WBS) 9 months after remnant ablation, or no visible uptake in the original thyroid bed on a post therapeutic WBS when a second high dose was necessary.

RESULTS

After interim analysis of the first 8 patients, the failure rate was estimated to be 69% (90% confidence interval (CI) 20-86%) and the inclusion of new patients had to be stopped. Final analysis resulted in an ablation success in 11 out of 17 patients (65%, 95% CI 38-86%).

CONCLUSION

According to this study, the efficacy of rhTSH in the preparation of 131I ablation therapy is inferior, when using a strict definition of ablation success. The current lack of agreement as to the definition of successful remnant ablation, makes comparison between different ablation strategies difficult. Our results point to the need for an international consensus on the definition of ablation success, not only in routine patient's care but also for scientific reasons.

TRIAL REGISTRATION

Dutch Trial Registration NTR2395.

Low versus high radioiodine activity to ablate the thyroid after thyroidectomy for cancer: a meta-analysis of randomized controlled trials

It is not known whether low-dose radioiodine is as effective as high-dose radioiodine for treating patients with differentiated thyroid cancer after surgery. This study compared ablation success rates of different doses of radioiodine in patients with differentiated thyroid cancer after thyroidectomy. Fifteen randomized controlled trials were obtained from PubMed, Embase, and Cochrane Library (1966 to February 2013). Stata version 12.0 was used to pool the outcomes. Mantel-Haenszel (MH) and inverse variance (IV) methods were used in a fixed-effects and random-effects model, respectively. The relative risk (RR) with 95% confidence interval (CI) was used to compare the success rates of different doses of radioiodine. There were a total of 3,046 patients. The pooled RR for comparing ablation success with low- and high-dose radioiodine was 0.90 (95% CI 0.83-0.98, IV). Excluding a study with a distinctive outcome, sensitivity analysis showed that the pooled RR was 0.95 (95% CI 0.92-0.99, MH). In subgroup analysis, the pooled RR of three studies that only administrated radioiodine to patients with pT2-4 cancer was 0.93 (95% CI 0.83-1.04, MH); the pooled RR of five studies with total thyroidectomy for all patients was 0.96 (95% CI 0.92-1.00, MH); and the pooled RR of four studies that used thyrotropin α to stimulate serum thyrotropin was 0.96 (95% CI 0.90-1.02, MH). The pooled RRs for comparing ablation success for moderate-dose versus high-dose and low-dose radioiodine were 0.94 (95% CI 0.85-1.04, IV) and 0.87 (95% CI 0.73-1.04, IV), respectively. Low-dose radioiodine can be used in patients undergoing total thyroidectomy. For those who receive insufficient surgical treatment, high-dose radioiodine is more appropriate.

Alkylphosphocholine analogs for broad-spectrum cancer imaging and therapy

Many solid tumors contain an overabundance of phospholipid ethers relative to normal cells. Capitalizing on this difference, we created cancer-targeted alkylphosphocholine (APC) analogs through structure-activity analyses. Depending on the iodine isotope used, radioiodinated APC analog CLR1404 was used as either a positron emission tomography (PET) imaging ((124)I) or molecular radiotherapeutic ((131)I) agent. CLR1404 analogs displayed prolonged tumor-selective retention in 55 in vivo rodent and human cancer and cancer stem cell models. (131)I-CLR1404 also displayed efficacy (tumor growth suppression and survival extension) in a wide range of human tumor xenograft models. Human PET/CT (computed tomography) and SPECT (single-photon emission computed tomography)/CT imaging in advanced-cancer patients with (124)I-CLR1404 or (131)I-CLR1404, respectively, demonstrated selective uptake and prolonged retention in both primary and metastatic malignant tumors. Combined application of these chemically identical APC-based radioisosteres will enable personalized dual modality cancer therapy of using molecular (124)I-CLR1404 tumor imaging for planning (131)I-CLR1404 therapy.

Controversies about radioactive iodine-131 remnant ablation in low risk thyroid cancers: are we near a consensus?

Well differentiated thyroid cancers (WDTC), including papillary (80%) and follicular (10%) types, are the most common endocrine cancers globally. Over the last few decades most the diagnosed cases have fallen into low risk categories. Radioactive iodine-131 (RAI) has an established role in reducing recurrence and improving the survival in high risk patients. In patients with primary tumor size <1 cm, RAI is not recommended by many thyroid societies. However, low risk WDTC has been an arena of major controversies, most importantly the role and dose of adjuvant RAI for remnant ablation to minimize chances of recurrence and improving survival. This review is an attempt to update readers about the previous and existing practice based on results of non- randomized trials and evolving trends fueled by recently published randomized studies.

One size does not fit all: the merit of absorbed doses to the blood in 131I therapy for differentiated thyroid carcinoma

The amount of 131I necessary for successful ablation in patients with differentiated thyroid cancer (DTC) is still subject to debate. This study investigates the relationship of the absorbed dose of radiation to the blood while administering 131I activity with several other parameters in DTC patients. This prospective study included 90 DTC patients who were classified into three groups according to their level of dosage: 3.7 GBq (38.9%), 5.55 GBq (55.6%), and 7.4 GBq (5.5%). Blood dosimetry of treated patients was performed using external whole-body counting with a Geiger Muller dosimeter located 2 m away from the patients. Dose rate was measured at 2, 4, 5, 24, and 48 h after the administration of radioiodine. Based on the results of whole-body dose rate measurements, 48 h after administration of 3.7, 5.55, and 7.4 GBq of radioiodine, absorbed doses to patients' blood were estimated at 0.49 ± 0.12, 0.71 ± 0.21, and 0.76 ± 0.11 Gy, respectively. Increasing radioiodine dosage from 3.7 GBq to 5.55 GBq significantly increased blood dose, while there was no significant difference in blood dose between radioiodine dosages of 5.55 GBq and 7.4 GBq. The absorbed dose to the blood was significantly correlated to the patients' gender and the presence of lymph node metastases, but it was not significantly correlated to the type of pathology and regional or distant metastases. Ablation activities exceeding 5.55 GBq produce no further increase in the accumulated activity per volume of blood. The literature regarding this issue is scarce, and further studies are required to verify these preliminary results.

Codon-optimized human sodium iodide symporter (opt-hNIS) as a sensitive reporter and efficient therapeutic gene

To generate a more efficient in vivo reporter and therapeutic gene, we optimized the coding sequence of the human sodium/iodide symporter (NIS) gene by replacing NIS DNA codons from wild type to new codons having the highest usage in human gene translation. The Codon Adaptation Index (CAI), representing the number of codons effective for human expression, was much improved (0.79 for hNIS, 0.97 for opt-hNIS). Both wild-type (hNIS) and optimized human NIS (opt-hNIS) were cloned into pcDNA3.1 and pMSCV vectors for transfection. Various cancer cell lines such as thyroid (TPC-1, FRO, B-CPAP), breast (MDA-MB-231), liver (Hep3B), cervical (HeLa), and glioma (U87MG) were transfected with pcDNA3.1/hNIS or pcDNA3.1/opt-hNIS. ¹²⁵I uptake by opt-hNIS-expressing cells was 1.6 ~ 2.1 times higher than uptake by wild-type hNIS-expressing cells. Stable cell lines were also established by retroviral transduction using pMSCV/hNIS or pMSCV/opt-hNIS, revealing higher NIS protein levels and ¹²⁵I uptake in opt-hNIS-expressing cells than in hNIS-expressing cells. Moreover, scintigraphic images from cell plates and mouse xenografts showed stronger signals from opt-hNIS-expressing cells than hNIS-expressing cells, and radioactivity uptake by opt-hNIS-expressing tumors was 2.3-fold greater than that by hNIS-expressing tumors. To test the efficacy of radioiodine therapy, mouse xenograft models were established with cancer cells expressing hNIS or opt-hNIS. ¹³¹I treatment reduced tumor sizes of hNIS- and opt-hNIS-expressing tumors to 0.57- and 0.27- fold, respectively, compared to their sizes before therapy, suggesting an improved therapeutic effect of opt-hNIS. In summary, this study shows that codon optimization strongly increases hNIS protein levels and radioiodine uptake, thus supporting opt-hNIS as a more sensitive reporter and efficient therapeutic gene.

The AEC/NRC 30 mCi rule: regulatory origins and clinical consequences for 131I remnant ablative doses

BACKGROUND

Clinical and historical uncertainty exists surrounding the regulations of the Atomic Energy Commission/Nuclear Regulatory Commission (AEC/NRC) requiring patient hospitalization when (131)I activities exceed 30 mCi. This review investigates the sometimes disturbing regulatory and clinical origins and consequences of the use of this low, 30 mCi dose as a prescription for thyroid remnant ablation.

SUMMARY

As early as in the 1940s, activities of (131)I between 30 and 200 mCi, often fractionated, were employed. The AEC deliberated from 1947 to the early 1960s before imposing as a license condition the requirement of hospitalizing patients until they contained <30 mCi of any byproduct material. The written AEC record throughout these years contains no supportive data to suggest safety issues requiring hospitalization at this activity level of (131)I. Yet the techniques for making the necessary calculations for determining radiation safety were available at this time. Declarations on the subject by nongovernmental bodies were misinterpreted as confirming such hospitalization as a legal requirement. The 30 mCi license condition was codified into NRC regulations in 1987 and was subsequently removed in 1997. Without any data, these U.S. regulatory agencies caused significant expense, inconvenience, and fear, affecting thyroid cancer patients and their families. This 30 mCi regulatory activity limit morphed, by a fortunate coincidence, into an acceptable ablative activity before there were solid confirmatory data. Studies on this 30 mCi ablative dose indicate that this activity was never associated with radiation health and safety issues, and was never more effective than higher ablative doses but led slightly more often to the need for a second (131)I dose. Nevertheless, the available data generally support the American Thyroid Association and Society of Nuclear Medicine and Molecular Imaging Guidelines, which indicate, without a treatment activity preference, that 30-100 mCi of (131)I provide adequate ablation. Follow-up data on the rates of recurrences, deaths, and second primary malignancies within this range of doses are unavailable.

CONCLUSIONS

This history of unjustified governmental action and blind acceptance must remind the medical/radiation safety community to require solid data before ever again adopting baseless requirements. The 30 mCi dose should have never been employed as a requirement for hospitalization.

Comparison between low and high radioactive iodine (131I) reablation dose in patients with papillary thyroid cancer

AIM

The aim of this study was to assess ablation outcome after a second ablation dose and compare the ablation rate after low and high reablation doses of iodine-131 ((131)I) after failure of the first ablation with 3700 MBq.

PATIENTS AND METHODS

The study included 81 patients with papillary thyroid cancer; they failed to achieve complete ablation after a first ablative dose of 3700 MBq. Their first follow-up (131)I whole-body scan carried out 6-9 months after ablation showed small residual functioning tissue in the thyroid bed, with no functioning metastases. This is associated with unsuppressed serum thyroglobulin level (Tg) higher than 2 ng/ml. The patients received a second ablation dose, which was low (1110 MBq) in 37 patients and high in the remaining 44 patients (2960 MBq in 36 patients and 3700 MBq in eight patients). A whole-body scan and Tg level assessment were carried out 6-9 months later. The criteria for complete ablation included absence of residual functioning thyroid tissue and a Tg level lower than 2 ng/ml.

RESULTS

The overall successful complete ablation rate after the second reablation dose was 75%. This was achieved in 27 of 37 patients (73%) who received a low reablation dose and in 34 of 44 patients (77%) who received a high reablation dose; no statistically significant difference was found between the two groups (P>0.05).

CONCLUSION

In patients with papillary thyroid cancer who failed to achieve complete ablation after the first ablation dose of 3700 MBq, the overall complete ablation rate after both a low and a high second (131)I dose was 75%, with no statistically significant difference in ablation rate between low (1110 MBq) and high (2960 and 3700 MBq) doses (73 and 77%, respectively).

Selective capture of iodide from solutions by microrosette-like δ-Bi₂O₃

Radioactive iodine isotopes that are produced in nuclear power plants and used in medical research institutes could be a serious threat to the health of many people if accidentally released to the environment because the thyroid gland can absorb and concentrate them from a liquid. For this reason, uptake of iodide anions was investigated on microrosette-like δ-Bi2O3 (MR-δ-Bi2O3). The MR-δ-Bi2O3 adsorbent showed a very high uptake capacity of 1.44 mmol g(-1) by forming insoluble Bi4I2O5 phase. The MR-δ-Bi2O3 also displayed fast uptake kinetics and could be easily separated from a liquid after use because of its novel morphology. In addition, the adsorbent showed excellent selectivity for I(-) anions in the presence of large concentrations of competitive anions such as Cl(-) and CO3(2-), and could work in a wide pH range of 4-11. This study led to a new and highly efficient Bi-based adsorbent for iodide capture from solutions.

Differentiated thyroid cancer-personalized therapies to prevent overtreatment

The concept of individualized therapy is rapidly gaining recognition in the management of patients with differentiated thyroid cancer (DTC). This Review provides an overview of the most important elements of this paradigm shift in DTC management and discusses the implications for clinical practice. In the majority of patients with DTC who have an inherently good prognosis, the extent of surgery, the dosage of (131)I therapy and the use of levothyroxine therapy are all aspects suitable for individualization, on the basis of both the stage of disease and the response to treatment. In individuals with advanced disease, newer imaging techniques, advances in (131)I therapy and the use of targeted molecular therapies (such as multitargeted kinase inhibitors) have provided new options for the personalized care of patients, for whom until recently no effective therapies were available. Individualized therapies could reduce adverse effects, including the sometimes debilitating hypothyroidism that used to be required before initiation of (131)I treatment, and major salivary gland damage, a common and unpleasant side effect of (131)I therapy. Highly individualized interdisciplinary treatment of patients with DTC might lead to improved outcomes with reduced severity and frequency of complications and adverse effects. However, in spite of ongoing research, personalized therapies remain in their infancy.

Radioiodine ablation with 1,850 MBq in association with rhTSH in patients with differentiated thyroid cancer

PURPOSE

The aim of this study was to evaluate the efficacy of post-operative radioiodine ablation with 1,850 MBq after recombinant human thyrotropin (rhTSH) administration in patients with differentiated thyroid carcinoma (DTC). We also aimed to assess the prognostic role of several patient features on the outcome of ablation.

METHODS

We retrospectively analyzed data from a total of 125 patients with DTC who underwent post-operative radioiodine ablation with 1,850 MBq of ¹³¹I after preparation with rhTSH. One injection of 0.9 mg rhTSH was administered on each of two consecutive days; ¹³¹I therapy was delivered 24 h after the last injection, followed by a post-therapy whole-body scan. Successful ablation was assessed 6-12 months later and defined as an rhTSH-stimulated serum thyroglobulin (Tg) level ≤1.0 ng/ml and a normal neck ultrasound.

RESULTS

Patients were stratified according to the American Thyroid Association (ATA) Management Guidelines for Differentiated Thyroid Cancer. Successful ablation was achieved in 82.4 % of patients, with an ablation rate of 95.1 % in low-risk patients and 76.2 % in intermediate-risk patients. Analyzing the correlation between ablation outcome and patient characteristics, we found a statistically significant association between failure to ablate and class of risk based on ATA guidelines (p = 0.025) and a stimulated Tg value at ablation of above 5 ng/ml (p < 0.001).

CONCLUSION

The use of 1,850 MBq post-operative radioiodine thyroid remnant ablation in association with rhTSH is effective for low- and intermediate-risk patients. Moreover, in our study, we found a statistical correlation between failure to ablate and class of risk based on ATA guidelines for DTC and a stimulated Tg value at ablation.