Radioiodine therapy dosimetry in benign thyroid disease and differentiated thyroid carcinoma

Investigation of the Suitability of a Commercial Radiation Sensor for Pretherapy Dosimetry of Radioiodine Treatment Patients

Radioiodine (I-131) therapy is routinely used to treat conditions of the thyroid. Dosimetry planning in advance of I-131 therapy has been shown to improve patient treatment outcomes. However, this pretherapy dosimetry step requires multiple outpatient appointments and is not feasible for patients living at greater distances. Here, the feasibility of a commercially available smartphone-operated radiation sensor (Smart Geiger Pro, Technonia) for at-home patient pretherapy dosimetry has been investigated. The influence of both treatment-specific parameters (radioisotope activity, gamma photon energy, patient size) and external factors (sensor placement and motion) on the ability of the radiation sensor to accurately quantify radiation dose rates has been studied. The performance limits of the radiation sensor have been identified. A preliminary trial of the sensor on four I-131 patients prior to their therapy, conducted at the Nuclear Medicine/Endocrinology departments of St James's Hospital Dublin, is also presented. A comparable performance between the low-cost radiation sensor and that of a hospital-grade thyroid uptake probe is reported. This work demonstrates the potential of low-cost commercially available radiation sensors as a solution for at-home pretherapy dosimetry for long distance patients, or indeed for hospitals who wish to implement dosimetry at reduced cost. Recommended conditions for optimum sensor performance use are presented.

Gender differences in estimating I-131 thyroid uptake from Tc-99m thyroid uptake for benign thyroid disease

OBJECTIVE

For radioactive Iodine-131 (¹³¹I) treatments of thyroid diseases, increased efficacy has been reported for personalized dosimetry treatments. The measurement of Iodine-131 thyroid uptake (¹³¹IU) is required in these cases. This study aims to investigate whether ^99mTc thyroid uptake (^99mTcU) may be used in place of ¹³¹IU for implementing personalised treatments.

METHODS

A retrospective study of 152 benign thyroid disease ¹³¹I treatments was carried out during 2012-2020; 117 treatments were for female patients while 35 were for male patients diagnosed with either Graves' disease, multinodular goitre or toxic nodules.

RESULTS

A statistically significant correlation was found between ¹³¹IU and ^99mTcU data, with the data more correlated for male than female patients (r = 0.71 vs 0.38, p-value < 0.001). Patient age and time difference between the two respective uptake measurements significantly influenced the uptake correlation in females but not for the male cohort, although there was no significant difference between the parameters across gender. Thyroid diagnosis and hormone levels showed a significant correlation with uptakes in both genders. Estimating ¹³¹IU based on ^99mTcU was shown to be predictive for male but not in female patients (R² = 91% vs 16%).

CONCLUSION

Estimating ¹³¹IU based on ^99mTcU is not recommended for females at our centre. Males reported good correlation, but a larger sample would be needed for validation.

ADVANCES IN KNOWLEDGE

The initial findings showed a significant gender difference in benign thyroid uptake parameters at our centre, highlighting the potential need for gender consideration when planning ¹³¹IU patient management and when reporting studies results.

Nine Genes Mediate the Therapeutic Effects of Iodine-131 Radiotherapy in Thyroid Carcinoma Patients

Background

Thyroid carcinoma (THCA) is one of the most common malignancies of the endocrine system, which is usually treated by surgery combined with iodine-131 (I¹³¹) radiotherapy.

Aims

This study is aimed at exploring the potential targets of I¹³¹ radiotherapy in THCA.

Methods

The RNA-sequencing data of THCA in The Cancer Genome Atlas database (including 568 THCA samples) was downloaded. The differentially expressed genes (DEGs) between the tumour samples whether or not subjected to I¹³¹ radiotherapy were identified using edgeR package. Using the WGCNA package, the module that was relevant with I¹³¹ radiotherapy was selected. The intersection genes of the hub module nodes and the DEGs were obtained as hub genes, followed by the function and pathway enrichment analyses using the clusterProfiler package. Moreover, the protein-protein interaction (PPI) network for the hub genes was constructed using Cytoscape software. In addition, more important hub genes were analysed with function mining using the GenCLiP2 online tool. The qPCR analysis was used to verify the mRNA expression of more important hub genes in THCA tissues.

Results

There were 500 DEGs (167 upregulated and 333 downregulated) between the two groups. WGCNA analysis showed that the green module (428 nodes) exhibited the most significant correlation with I¹³¹ radiotherapy. A PPI network was built after the identification of 53 hub genes. In the PPI network, CDH5, KDR, CD34, FLT4, EMCN, FLT1, ROBO4, PTPRB, and CD93 exhibited higher degrees, which were mainly implicated in the vascular function. The relative expression of nine mRNAs in the THCA tissues treated with I¹³¹ was lower.

Conclusion

I¹³¹ radiotherapy might exert therapeutic effects by targeting CDH5, KDR, CD34, FLT4, EMCN, FLT1, ROBO4, PTPRB, and CD93 in THCA patients.

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.

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

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

Salivary evaluation in radioactive I131 treated patients with thyroid carcinoma

BACKGROUND AND OBJECTIVE

radioiodine treatment (I¹³¹) used to treat thyroid carcinomas produces side effects (sialadenitis, xerostomia, dysphagia and caries susceptibility) reflecting in a poor patient quality of life. This study aimed to evaluate the effect of I¹³¹ on salivary function and possible oral impairment.

MATERIAL AND METHODS

Thirty-seven patients undergoing I¹³¹ were submitted to oral examination, answer questions regarding xerostomia/hyposalivation and collect saliva at three moments (M1: 30-45 days before I¹³¹, M2: 1-2 days after I¹³¹ and M3: 7-10 days after treatment). Saliva was assayed for flow rate and calcium/phosphate concentrations.

RESULTS AND CONCLUSIONS

significant difference in calcium/phosphate concentration was shown between M1 and M2, with evident decrease at M2. Flow rate reduced right after treatment with 41% of patients returning to previous rate at M3 (no statistical difference). A higher number of patients related xerostomia and difficulty in swallowing food at M2. The results showed that xerostomia/hyposalivation, dysphagia and calcium/phosphate concentration decrease may be considered early radioiodine side effects.

Rutin Scavenges Reactive Oxygen Species, Inactivates 5'-Adenosine Monophosphate-Activated Protein Kinase, and Increases Sodium-Iodide Symporter Expression in Thyroid PCCL3 Cells

BACKGROUND

Thyroid iodide uptake, mediated by the sodium-iodide symporter (NIS), is essential for thyroid hormone synthesis and also for treatment of thyroid diseases, such as thyroid cancer, through radioiodine therapy. Therefore, compounds able to increase thyroid iodide uptake could be clinically useful, and it is of great importance to unravel the mechanisms underlying such an effect. It has been shown previously that the flavonoid rutin increases thyroid radioiodide uptake in vivo in rats. This study aimed to investigate the mechanisms involved in the stimulatory effect of rutin on iodide uptake.

METHODS

This study evaluated iodide uptake, NIS expression and its subcellular distribution, iodide efflux, reactive oxygen species levels, and the intracellular pathways involved in NIS regulation in a rat thyroid PCCL3 cell line treated with rutin.

RESULTS

Similar to previous results found in vivo, rutin increased radioiodide uptake in PCCL3 cells, which was accompanied by increased NIS expression (at both the mRNA and protein levels) and a reduction of radioiodide efflux. Moreover, the results suggest that rutin could regulate NIS subcellular distribution, leading to higher levels of NIS at the cell membrane. In addition, rutin decreased the levels of intracellular reactive oxygen species and phospho-5'-adenosine monophosphate-activated protein kinase.

CONCLUSIONS

The flavonoid rutin seems to be an important stimulator of radioiodide uptake, acting at multiple levels, an effect that can be due to decreased oxidative stress, reduced 5'-adenosine monophosphate-activated protein kinase activation, or both. Since thyroid iodide uptake is crucial for effective radioiodine therapy, the results suggest that rutin could be useful as an adjuvant in radioiodine therapy.

I-131 biokinetics of remnant normal thyroid tissue and residual thyroid cancer in patients with differentiated thyroid cancer: comparison between recombinant human TSH administration and thyroid hormone withdrawal

OBJECTIVE

The aim of this study was to assess I-131 biokinetics in thyroid cancer and remnant tissue in patients with differentiated thyroid cancer using whole-body scan (WBS) and SPECT images acquired after I-131 therapy. The influence of thyroid stimulating hormone (TSH) stimulation method on the kinetics was also evaluated.

METHODS

A total of 57 patients who received I-131 therapy (2.96-7.4 GBq) were retrospectively included. TSH stimulation was achieved by recombinant human thyrotropin (rhTSH) or by thyroid hormone withdrawal (THW). Each patient received three sequential WBSs on days 1, 2, and 4 (or 5) after I-131 administration. All lesions were classified either as thyroid remnant (ThyR) or as metastatic lymph nodes (mLN) after considering the SPECT/CT images acquired during the last WBS. The lesion-based retention rate and absorbed dose of ThyR and mLN were calculated using a commercial dosimetric toolkit combined with the OLINDA software.

RESULTS

The retention rate and the effective half-time of mLN were lower than that of ThyR (p < 0.001, p = 0.003). In addition, the retention rate and the effective half-time of ThyR in the rhTSH group were higher than those in the THW group (p < 0.001, p < 0.001). The differences in the retention rate and the effective half-time of mLN were not statistically significant between the THW group and rhTSH group (p = 0.549, p = 0.571).

CONCLUSIONS

Radioiodine therapy using rhTSH delivered an at least similar radiation dose to target lesions compared to using THW in thyroid remnants and metastatic lymph nodes.

Comparing pre-therapeutic 124I and 131I uptake tests with intra-therapeutic 131I uptake in benign thyroid disorders

PURPOSE

¹²⁴I-PET/CT can be used for pre-therapeutic assessment of radioactive iodine uptake in benign thyroid disorders, however systematic comparisons with intra-therapeutic uptake are still lacking for these disorders. The goals of this study were to compare ¹²⁴I RAIU and conventional ¹³¹I RAIU tests with each other; to compare both tests with intra-therapeutic uptake (reference); and to verify the time course of radioactive iodine uptake at three time points (30, 102, and 336 h [14 days] post administration; p.a.).

METHODS

Thirteen patients with benign thyroid diseases underwent ¹³¹I RAIU test and ¹²⁴I RAIU test one after another before the intra-therapeutic ¹³¹I uptake (reference) was measured via short-range and long-range measurements. After correction for decay, relative uptake differences were calculated and subjected to the Bland-Altman method for the evaluation of levels of agreement.

RESULTS

Radioactive iodine uptake tests with ¹²⁴I-PET/CT and ¹³¹I probe did not show systematic deviations at any time point. Likewise, at 30 and 102 h p.a. there was no systematic discrepancy between pre-therapeutic and intra-therapeutic uptake levels. At 14 days p.a., however, both pre-therapeutic tests tended to overestimate the uptake compared to reference. Findings showed, for the first time with ¹²⁴I, that radioiodine therapy has some early radiobiological effects possibly limiting the accuracy of pre-therapeutic dosimetry.

CONCLUSIONS

¹²⁴I RAIU tests represent a feasible alternative to standard ¹³¹I RAIU tests. The additional benefits of ¹²⁴I-PET/CT (e.g., functional topography, inclusion of retrosternal areas, possibility to enable fusion imaging) may thus increase the scope of this technology in benign thyroid disorders.

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

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

A new method to evaluate the residual activity in patients undergoing (131)I thyroid therapy

The radioiodine administration is a standard therapeutic approach to both benign thyroid diseases, such as hyperthyroidism, and carcinomas. The high administered (131)I activities are of radiation protection concern, due to relevant patient residual contamination. The aim of this work was to develop a new procedure based on external radiometric surveys and on a mathematical model in order to estimate the (131)I activity in patients undergoing hyperthyroidism radioiodine therapy. In the first stage of this study, a suitable detector was chosen and its response vs. activity was characterized. The experimental verification was performed measuring the ambient dose equivalent rate from patients receiving radioiodine administration. The results confirm the reliability of the proposed method, as shown by the slight differences between the administered activities and the ones calculated from external measurements. Furthermore, the same procedure was applied to detect the percentage residual activity in patients at two preset time intervals: 4 hours and 4 days after the radioiodine administration. The obtained results clearly highlight that the method can ensure a level of reliability compatible with the radiation protection purposes.

The evidence base for the use of internal dosimetry in the clinical practice of molecular radiotherapy

Molecular radiotherapy (MRT) has demonstrated unique therapeutic advantages in the treatment of an increasing number of cancers. As with other treatment modalities, there is related toxicity to a number of organs at risk. Despite the large number of clinical trials over the past several decades, considerable uncertainties still remain regarding the optimization of this therapeutic approach and one of the vital issues to be answered is whether an absorbed radiation dose-response exists that could be used to guide personalized treatment. There are only limited and sporadic data investigating MRT dosimetry. The determination of dose-effect relationships for MRT has yet to be the explicit aim of a clinical trial. The aim of this article was to collate and discuss the available evidence for an absorbed radiation dose-effect relationships in MRT through a review of published data. Based on a PubMed search, 92 papers were found. Out of 79 studies investigating dosimetry, an absorbed dose-effect correlation was found in 48. The application of radiobiological modelling to clinical data is of increasing importance and the limited published data on absorbed dose-effect relationships based on these models are also reviewed. Based on National Cancer Institute guideline definition, the studies had a moderate or low rate of clinical relevance due to the limited number of studies investigating overall survival and absorbed dose. Nevertheless, the evidence strongly implies a correlation between the absorbed doses delivered and the response and toxicity, indicating that dosimetry-based personalized treatments would improve outcome and increase survival.

EANM Dosimetry Committee series on standard operational procedures for pre-therapeutic dosimetry II. Dosimetry prior to radioiodine therapy of benign thyroid diseases

The EANM Dosimetry Committee Series "Standard Operational Procedures for Pre-Therapeutic Dosimetry" (SOP) provides advice to scientists and clinicians on how to perform patient-specific absorbed dose assessments. This particular SOP describes how to tailor the therapeutic activity to be administered for radioiodine therapy of benign thyroid diseases such as Graves' disease or hyperthyroidism. Pretherapeutic dosimetry is based on the assessment of the individual (131)I kinetics in the target tissue after the administration of a tracer activity. The present SOP makes proposals on the equipment to be used and guides the user through the measurements. Time schedules for the measurement of the fractional (131)I uptake in the diseased tissue are recommended and it is shown how to calculate from these datasets the therapeutic activity necessary to administer a predefined target dose in the subsequent therapy. Potential sources of error are pointed out and the inherent uncertainties of the procedures depending on the number of measurements are discussed. The theoretical background and the derivation of the listed equations from compartment models of the iodine kinetics are explained in a supplementary file published online only.

Radioiodine therapy in benign thyroid diseases: effects, side effects, and factors affecting therapeutic outcome

Radioiodine ((131)I) therapy of benign thyroid diseases was introduced 70 yr ago, and the patients treated since then are probably numbered in the millions. Fifty to 90% of hyperthyroid patients are cured within 1 yr after (131)I therapy. With longer follow-up, permanent hypothyroidism seems inevitable in Graves' disease, whereas this risk is much lower when treating toxic nodular goiter. The side effect causing most concern is the potential induction of ophthalmopathy in predisposed individuals. The response to (131)I therapy is to some extent related to the radiation dose. However, calculation of an exact thyroid dose is error-prone due to imprecise measurement of the (131)I biokinetics, and the importance of internal dosimetric factors, such as the thyroid follicle size, is probably underestimated. Besides these obstacles, several potential confounders interfere with the efficacy of (131)I therapy, and they may even interact mutually and counteract each other. Numerous studies have evaluated the effect of (131)I therapy, but results have been conflicting due to differences in design, sample size, patient selection, and dose calculation. It seems clear that no single factor reliably predicts the outcome from (131)I therapy. The individual radiosensitivity, still poorly defined and impossible to quantify, may be a major determinant of the outcome from (131)I therapy. Above all, the impact of (131)I therapy relies on the iodine-concentrating ability of the thyroid gland. The thyroid (131)I uptake (or retention) can be stimulated in several ways, including dietary iodine restriction and use of lithium. In particular, recombinant human thyrotropin has gained interest because this compound significantly amplifies the effect of (131)I therapy in patients with nontoxic nodular goiter.

Development of hypothyroidism during long-term follow-up of patients with toxic nodular goitre after radioiodine therapy

OBJECTIVE

To investigate the cure rate and incidence of hypothyroidism of radioiodine treatment with a calculated dose regimen and an intended thyroid dose of 150 Gy in patients with toxic nodular goitre during long-term follow-up.

PATIENTS

A total of 265 consecutive patients with toxic nodular goitre were treated between March 2003 and August 2004 at our institute and followed up for a maximum of 8 years. Preliminary radioiodine testing with volumetric measurement of the thyroid by ultrasound as well as individual thyroidal radioiodine uptake and half-life measurements were performed before radioiodine therapy. The estimated radiation dose to the thyroid was 150 Gy.

MEASUREMENTS

Follow-up controls with respect to success of therapy and development of hypothyroidism were performed 3 months, 1 and up to 8 years after radioiodine treatment. The relation of the achieved thyroid dose to the success rate of treatment and to the incidence of hypothyroidism was analysed.

RESULTS

The cure rates were 85% at 3 months, 98% at 1 year and 98% at the end of follow-up. Above an achieved thyroid dose of more than 120 Gy, there was no significant association between the dose achieved in the thyroid and the cure rate on follow-up. The incidences of hypothyroidism at 3 months, at 1 year and at the end of follow-up were 32%, 55% and 73%, respectively.

CONCLUSIONS

Radioiodine treatment with a calculated dose regimen is a highly effective treatment option in patients with toxic goitre with an overall success rate of 98%. However, radioiodine treatment with an intended thyroid dose of 150 Gy leads to a high incidence of hypothyroidism on long-term follow-up. This finding supports the suggestion that in future intended thyroid doses could be lowered in patients treated with a calculated dose regimen for toxic nodular goitre.

GATE based Monte Carlo simulation of planar scintigraphy to estimate the nodular dose in radioiodine therapy for autonomous thyroid adenoma

The recommended target dose in radioiodine therapy of solitary hyperfunctioning thyroid nodules is 300-400Gy and therefore higher than in other radiotherapies. This is due to the fact that an unknown, yet significant portion of the activity is stored in extranodular areas but is neglected in the calculatory dosimetry. We investigate the feasibility of determining the ratio of nodular and extranodular activity concentrations (uptakes) from post-therapeutically acquired planar scintigrams with Monte Carlo simulations in GATE. The geometry of a gamma camera with a high energy collimator was emulated in GATE (Version 5). A geometrical thyroid-neck phantom (GP) and the ICRP reference voxel phantoms "Adult Female" (AF, 16ml thyroid) and "Adult Male" (AM, 19ml thyroid) were used as source regions. Nodules of 1ml and 3ml volume were placed in the phantoms. For each phantom and each nodule 200 scintigraphic acquisitions were simulated. Uptake ratios of nodule and rest of thyroid ranging from 1 to 20 could be created by summation. Quantitative image analysis was performed by investigating the number of simulated counts in regions of interest (ROIs). ROIs were created by perpendicular projection of the phantom onto the camera plane to avoid a user dependant bias. The ratio of count densities in ROIs over the nodule and over the contralateral lobe, which should be least affected by nodular activity, was taken to be the best available measure for the uptake ratios. However, the predefined uptake ratios are underestimated by these count density ratios: For an uptake ratio of 20 the count ratios range from 4.5 (AF, 1ml nodule) to 15.3 (AM, 3ml nodule). Furthermore, the contralateral ROI is more strongly affected by nodular activity than expected: For an uptake ratio of 20 between nodule and rest of thyroid up to 29% of total counts in the ROI over the contralateral lobe are caused by decays in the nodule (AF 3 ml). In the case of the 1ml nodules this effect is smaller: 9-11% (AF) respectively 7-8% (AM). For each phantom, the dependency of count density ratios upon uptake ratios can be modeled well by both linear and quadratic regression (quadratic: r(2)>0.99), yielding sets of parameters which in reverse allow the computation of uptake ratios (and thus dose) from count density ratios. A single regression model obtained by fitting the data of all simulations simultaneously did not provide satisfactory results except for GP, while underestimating the true uptake ratios in AF and overestimating them in AM. The scintigraphic count density ratios depend upon the uptake ratios between nodule and rest of thyroid, upon their volumes, and their respective position in a non-trivial way. Further investigations are required to derive a comprehensive rule to calculate the uptake or dose ratios based on post-therapeutic scintigraphy.