Dysfunction of the Salivary and Lacrimal Glands After Radioiodine Therapy for Thyroid Cancer: Results of the START Study After 6-Months of Follow-Up

Background: Understanding of changes in salivary and lacrimal gland functions after radioactive iodine therapy (131I-therapy) remains limited, and, to date, no studies have evaluated dose-response relationships between absorbed dose from 131I-therapy and dysfunctions of these glands. This study investigates salivary/lacrimal dysfunctions in differentiated thyroid cancer (DTC) patients six months after 131I-therapy, identifies 131I-therapy-related risk factors for salivary/lacrimal dysfunctions, and assesses the relationships between 131I-therapy radiation dose and these dysfunctions. Methods: A cohort study was conducted involving 136 DTC patients treated by 131I-therapy of whom 44 and 92 patients received 1.1 and 3.7 GBq, respectively. Absorbed dose to the salivary glands was estimated using a dosimetric reconstruction method based on thermoluminescent dosimeter measurements. Salivary and lacrimal functions were assessed at baseline (T0, i.e., immediately before 131I-therapy) and six months later (T6) using validated questionnaires and salivary samplings, with and without stimulation of the salivary glands. Statistical analyses included descriptive analyses and random-effects multivariate logistic and linear regressions. Results: There was no difference between T0 and T6 in the level of parotid gland pain, nor was there difference in the number of patients with hyposalivation, but there were significantly more patients with dry mouth sensation and dry eyes after therapy compared with baseline. Age, menopause, depression and anxiety symptoms, history of systemic disease, and not taking painkillers in the past three months were found to be significantly associated with salivary or lacrimal disorders. Significant associations were found between 131I-exposure and salivary disorders adjusted on the previous variables: for example, per 1-Gy increase in mean dose to the salivary glands, odds ratio = 1.43 [CI 1.02 to 2.04] for dry mouth sensation, ß = -0.08 [CI -0.12 to -0.02] mL/min for stimulated saliva flow, and ß = 1.07 [CI 0.42 to 1.71] mmol/L for salivary potassium concentration. Conclusions: This study brings new knowledge on the relationship between the absorbed dose to the salivary glands from 131I-therapy and salivary/lacrimal dysfunctions in DTC patients six months after 131I-therapy. Despite the findings of some dysfunctions, the results do not show any obvious clinical disorders after the 131I-therapy. Nevertheless, this study raises awareness of the risk factors for salivary disorders, and calls for longer follow-up. Clinical Trials Registration: Number NCT04876287 on the public website (ClinicalTrials.gov).

Normal organ dosimetry for thyroid cancer patients treated with radioiodine as part of the multi-centre multi-national Horizon 2020 MEDIRAD project

PURPOSE

Dosimetry is rarely performed for the treatment of differentiated thyroid cancer patients with Na[131I]I (radioiodine), and information regarding absorbed doses delivered is limited. Collection of dosimetry data in a multi-centre setting requires standardised quantitative imaging and dosimetry. A multi-national, multi-centre clinical study was performed to assess absorbed doses delivered to normal organs for differentiated thyroid cancer patients treated with Na[131I]I.

METHODS

Patients were enrolled in four centres and administered fixed activities of 1.1 or 3.7 GBq of Na[131I]I using rhTSH stimulation or under thyroid hormone withdrawal according to local protocols. Patients were imaged using SPECT(/CT) at variable imaging time-points following standardised acquisition and reconstruction protocols. Whole-body retention data were collected. Dosimetry for normal organs was performed at two dosimetry centres and results collated.

RESULTS

One hundred and five patients were recruited. Median absorbed doses per unit administered activity of 0.44, 0.14, 0.05 and 0.16 mGy/MBq were determined for the salivary glands of patients treated at centre 1, 2, 3 and 4, respectively. Median whole-body absorbed doses for 1.1 and 3.7 GBq were 0.05 Gy and 0.16 Gy, respectively. Median whole-body absorbed doses per unit administered activity of 0.04, 0.05, 0.04 and 0.04 mGy/MBq were calculated for centre 1, 2, 3 and 4, respectively.

CONCLUSIONS

A wide range of normal organ doses were observed for differentiated thyroid cancer patients treated with Na[131I]I, highlighting the necessity for individualised dosimetry. The results show that data may be collated from multiple centres if minimum standards for the acquisition and dosimetry protocols can be achieved.

Quantitative Scintigraphy Evaluated the Relationship between 131I Therapy and Salivary Glands Function in DTC Patients: A Retrospective Analysis

Purpose

Quantitative scintigraphy to evaluate salivary gland function changes in patients with differentiated thyroid cancer (DTC) after iodine-131 (¹³¹I) treatment.

Methods

A total of 458 patients with DTC grouped by sex and age were included. Salivary gland scintigraphy was performed to evaluate salivary gland function before and after ¹³¹I treatment. The uptake fraction (UF), uptake index (UI), and excretion fraction (EF) of two pairs of parotid glands and submandibular glands were measured and compared. The Chi-square test was conducted according to function impairment count.

Results

Salivary gland function in different age groups and sexes were quite different, especially for women <55 years old, who had decreased UF, UI, and EF of all four glands without basal injury. The secretion or uptake function of some salivary glands with basic function impairment before ¹³¹I treatment was increased after iodine treatment. Only a small percentage of males showed reduced functional parameters after several treatments. The most significant difference in the count of impairment for the four salivary glands were the first and third examinations, which was more evident in women. The submandibular gland had the most significant reduction in uptake.

Conclusion

Changes in salivary gland function are more common in young females being treated for DTC. Impairment of salivary gland function is correlated with the number of treatments and the cumulative dose of ¹³¹I. Some salivary gland functions impaired before ¹³¹I treatment were enhanced in the early treatment.

PSMA PET/CT Identifies Intrapatient Variation in Salivary Gland Toxicity From Iodine-131 Therapy

Introduction:

Xerostomia is a well-known complication after iodine-131 (¹³¹I) therapy for thyroid carcinoma. It is currently insufficiently understood how the dose and biodistribution of ¹³¹I relates to salivary gland toxicity, and whether this is consistent for all salivary glands within a single patient. Prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) was recently introduced as a new tool to evaluate the relative loss of vital acinar cells in individual salivary glands. We aimed to assess gland-specific salivary gland toxicity after ¹³¹I-therapy using PSMA PET/CT.

Methods:

Five patients with differentiated thyroid cancer underwent [⁶⁸Ga]Ga-PSMA-11 PET/CT to evaluate their eligibility for peptide radioligand therapy with [¹⁷⁷Lu]Lu-PSMA-617. Uptake patterns in salivary glands were evaluated visually and quantitatively as an indicator of vital acinar cell loss after prior ¹³¹I-therapy.

Results:

Four of 5 patients demonstrated significant lowered uptake in at least one salivary gland, after receiving at least 2 ¹³¹I-treatments. Asymmetric loss of vital acinar cells occurred by gland type (parotid/submandibular) and location (right/left). The other salivary glands in these patients and all salivary glands in the fifth patient showed normal uptake, demonstrating high intrapatient and interpatient variability.

Conclusions:

¹³¹I-therapy can induce salivary gland toxicity with high inter- but also high intrapatient variation among separate gland locations, which can be assessed with PSMA PET/CT. This new technique offers potential to guide further development and evaluation of protective measures in patients receiving ¹³¹I-therapy.

The salivary glands as a dose limiting organ of PSMA- targeted radionuclide therapy: A review of the lessons learnt so far

At present, prostate cancer remains the second most occurring cancer in men, in Europe. Treatment efficacy for therapy of advanced metastatic disease, and metastatic castration-resistant prostate cancer in particular is limited. Prostate-specific membrane antigen (PSMA) is a promising therapeutic target in prostate cancer, seeing the high amount of overexpression on prostate cancer cells. Clinical investigation of PSMA-targeted radionuclide therapy has shown good clinical efficacy. However, adverse effects are observed of which salivary gland hypofunction and xerostomia are among the most prominent. Salivary gland toxicity is currently the dose-limiting side effect for PSMA-targeted radionuclide therapy, and more specifically for PSMA-targeted alpha therapy. To date, mechanisms underlying the salivary gland uptake of PSMA-targeting compounds and the subsequent damage to the salivary glands remain largely unknown. Furthermore, preventive strategies for salivary gland uptake or strategies for treatment of salivary gland toxicity are needed. This review focuses on the current knowledge on uptake mechanisms of PSMA-targeting compounds in the salivary glands and the research performed to investigate different strategies to prevent or treat salivary gland toxicity.

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.

Evaluation of Radiation dosimetry of 99mTc-HYNIC-PSMA and imaging in prostate cancer

This study aims to evaluate the radiation dosimetry of a new technetium-99m‒labelled small-molecule inhibitor of prostate-specific membrane antigen (HYNIC-Glu-Urea-A, ^99mTc-HYNIC-PSMA) and its feasibility as a tumor-imaging agent in prostate cancer (PCa) patients. A total of 15 PCa patients were enrolled in this study. For the dosimetry study, 5 PCa patients received whole-body planar scans at 0.5 h, 1 h, 2 h, 4 h and 8 h after ^99mTc-HYNIC-PSMA injection. The Dosimetry Toolkit (GE, Milwaukee) was used to process the data and segment the organs in the SPECT/CT images, which were then projected onto planar images. The organ-specific absorbed doses, total-body absorbed doses and ^99mTc-HYNIC-PSMA effective doses of patients were calculated using OLINDA/EXM 1.1 software. Whole-body SPECT/CT images were also acquired from additional 10 prostate patients to investigate the feasibility of ^99mTc-HYNIC-PSMA for imaging tumors by calculating the ratio of tumor-to-background tracer uptake at 2 h after 740 MBq administration. The total-body absorbed dose was 1.54E-03 ± 2.43E-04 mGy/MBq, and the effective dose was 3.72E-03 ± 4.5E-04 mSv/MBq. Compared to published studies of other similar PSMA tracers and ^99mTc-targeted conventional tracers, the absorbed doses of ^99mTc-HYNIC-PSMA in all organs showed that it could be used safely in the human body. In addition, ^99mTc-HYNIC-PSMA showed high tracer uptake (with a tumor-to-background ratio of 9.42 ± 2.62) in the malignant lesions of PCa patients, making it a promising radiopharmaceutical imaging method for site-specific management of PCa.

Salivary gland function in thyroid cancer patients with radioiodine administration history

AIM

Radioiodine (RAI) improves survival in patients with locally advanced or metastatic differentiated thyroid carcinoma (DTC). Although there has been an ongoing debate on RAI-induced salivary gland damage, published data have been inconsistent. Therefore, the purpose of our study was to compare salivary gland function in intermediate and high risk DTC patients after single or repeated RAI treatment with their age- and sex-matched RAI-naive counterparts.

METHODS

Uptake and excretion of parotid and submandibular glands were quantitatively evaluated using ^99mTc-pertechnetate salivary gland scintigraphy in 23 patients previously treated with RAI. Patients (median 9.25 GBq ¹³¹I-NaI; Q1-Q3: 5.55-16.65; range: 5.55-27.5) were divided into subgroups according to previously administered ¹³¹I-NaI activity using cut-off values 5.55 GBq and 9.25 GBq. Their salivary gland scintigraphy results were compared with RAI-naive patients using Mann-Whitney test.

RESULTS

Compared to RAI-naive patients, parotid glands pertechnetate uptake was significantly lower in those treated with > 9.25 GBq (P=0.034) and parotid glands excretion fraction was already decreased with RAI activities > 5.55 GBq (P=0.031). In submandibular glands, no statistically significant difference in either function was observed even with RAI activity > 9.25 GBq.

CONCLUSION

Our data suggest that RAI therapy using activities ≤ 5.55 GBq does not substantially decrease saliva production. Activities > 5.55 GBq may lead to significant decrease in parotid excretion, and activities > 9.25 GBq also diminish parotid uptake. Surprisingly, submandibular glands, providing majority of seromucinous saliva under basal condition, seem to be unaffected even by RAI activities above 9.25 GBq.

177Lu-DOTA-HYNIC-Lys(Nal)-Urea-Glu: Biokinetics, Dosimetry, and Evaluation in Patients with Advanced Prostate Cancer

SPECT/CT images in patients have demonstrated the ability of [99mTc]Tc-EDDA/HYNIC-Lys(Nal)-Urea-Glu ([99mTc]Tc-iPSMA) to detect tumors and metastases of prostate cancer. Considering that theranostics combines the potential of therapeutic and diagnostic radionuclides in the same molecular probe, the aim of this research was to estimate the biokinetics and dosimetry of 177Lu-DOTA-HYNIC-Lys(Nal)-Urea-Glu (177Lu-iPSMA) in healthy subjects and analyze the response in patients receiving 177Lu-iPSMA therapeutic doses. 177Lu-iPSMA was obtained from lyophilized formulations with radiochemical purities >98%. Whole-body images from five healthy subjects were acquired at 20 min, 6, 24, 48, and 120 h after 177Lu-iPSMA administration (185 MBq). The image sequence was used to extrapolate the 177Lu-iPSMA time-activity curves of each organ to adjust the biokinetic model and calculate the total number of disintegrations (N) that occurred in the source regions. N data were the input for the OLINDA/EXM code to calculate internal radiation doses. Ten patients (median age: 68 y; range 58-86 y) received from 1 to 4 cycles of 177Lu-iPSMA (3.7 or 7.4 GBq) every 8-10 weeks. Response was evaluated using the 68Ga-PSMA-ligand-PET/CT or 99mTc-iPSMA-SPECT/CT diagnostic images and serum PSA levels before and after 177Lu-iPSMA treatment. The blood activity showed a half-life value of 1.1 h for the fast component (T 1/2 α = ln2/0.614), 9.2 h for the first slow component (T 1/2 β = ln2/0.075), and 79.6 h for the second slow component (T 1/2 γ = ln2/0.008). The average absorbed doses were 0.23, 0.28, 0.88, and 1.17 Gy/GBq for the spleen, liver, kidney, and salivary glands. A total of 18 cycles were performed in 10 patients. A PSA decrease and some reduction of the radiotracer uptake (SUV) in tumor lesions occurred in 60% and 70% of the patients, respectively. 177Lu-iPSMA obtained from kit formulations showed high tumor uptake with good response rates in patients. The results obtained in this study warrant further clinical studies to establish the optimal number of treatment cycles and for evaluating the effect of this therapeutic agent on survival of patients.

Poor patient compliance with instructions for continuous sialogogues after 131 I therapy

OBJECTIVES

To analyze the role of patient compliance as a factor in evaluating the effectiveness of continuous sialogogues to prevent salivary side effects from ¹³¹ I therapy in differentiated thyroid cancer patients.

METHODS

Differentiated thyroid cancer patients who were clinically scheduled for an ¹³¹ I therapy at MedStar Washington Hospital Center between 2012 and 2013 were given instructions for continuous sialogogues per standard clinical protocol. The prospective survey was given at multiple time points.

RESULTS

Ninety-nine patients consented to participate of whom 94 participants had complete data. The mean prescribed ¹³¹ I activity was 121 ± 50 mCi (4.5 ± 1.9 GBq), range 27.5-288 mCi (1.0-10.7 GBq ). Overall, only 10% (9/94) of patients were compliant with continuous sialogogues. Even though all patients took sialogogues on the first day of post-therapy, 17% of participants did not continuously take sialogogues during the first day, 60% during the first night, and 72% on the second day despite rigorous instructions to continue for two days.

CONCLUSION

Despite repetitive instructions to use sialogogues continuously, most patients (90%) were not compliant. In future studies, strict monitoring and evaluation of patient compliance will be crucial when assessing the effect of continuous versus intermittent or delayed initiation of sialogogues.

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

BACKGROUND

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

RESULTS

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

CONCLUSIONS

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

99mTc-labeled PSMA inhibitor: Biokinetics and radiation dosimetry in healthy subjects and imaging of prostate cancer tumors in patients

The prostate-specific membrane antigen (PSMA) is expressed in epithelial cells of the prostate and highly overexpressed in 95% of advanced prostate cancers. The aims of this study was to estimate the biokinetics and dosimetry of ^99mTc-EDDA/HYNIC-iPSMA (^99mTc-labeled PSMA inhibitor) in eight healthy subjects and evaluate its usefulness as a tumor-imaging agent in eight prostate cancer patients.

METHODS

^99mTc-EDDA/HYNIC-iPSMA was obtained from a lyophilized formulation with radiochemical purities >98%, determined by reversed-phase HPLC and ITLC-SG analyses. Whole-body images from eight healthy subjects were acquired at 20min, and at 2, 6 and 24h after ^99mTc-EDDA/HYNIC-iPSMA administration. Regions of interest (ROIs) were drawn around the source organs on each time frame. Each ROI was corrected by background, attenuation, scattered radiation and physical decay. The image sequence was used to extrapolate the ^99mTc-EDDA/HYNIC-iPSMA time-activity curves of each organ to adjust the biokinetic model and calculate the total number of disintegrations (N) that occurred in the source regions. N data were the input for the OLINDA/EXM code to calculate internal radiation doses. In eight prostate cancer patients with histologically confirmed cancer, whole-body SPECT/CT images were obtained at 3h.

RESULTS

The blood activity showed a half-life value of 4.98min for the fast component (T_1/2α=ln2/8.34), 2.49h for the first slow component (T_1/2β=ln2/0.278), and 9.24h for the second slow component (T_1/2γ=ln2/0.076). Images from patients showed an average tumor/background ratio of 8.99±3.27 at 3h. The average equivalent doses calculated for a study using 740MBq were 3.80, 7.06, 9.69, 10.70, and 28.80mSv for the breast, spleen, salivary glands, liver, and kidneys respectively, with an effective dose of 3.42±0.78mSv.

CONCLUSIONS

All the absorbed doses were comparable to those known for most of the ^99mTc studies. ^99mTc-EDDA/HYNIC-iPSMA obtained from kit formulations showed high tumor uptake in patients with malignant lesions, making it a promising imaging radiopharmaceutical to target site-specific prostate cancer.

Systematic evaluation of salivary gland damage following I-131 therapy in differentiated thyroid cancer patients by quantitative scintigraphy and clinical follow-up

OBJECTIVES

Radioiodine therapy is a common adjunct to thyroidectomy in papillary thyroid cancer treatment. However, a variety of associated adverse effects have been reported. In this study, we assessed radioiodine-induced salivary gland dysfunction using quantitative scintigraphy, and evaluated the associated complications.

METHODS

Patients were divided into five groups on the basis of the cumulative I-131 dosage received. Scintigraphic dynamic images of the salivary glands were obtained and converted into clinically relevant parameters: uptake index (UI), maximum secretion rate (%SR), and combined gland function scores. Patients were followed up for 3-66 months and interviewed for side effects including xerostomia, taste alteration, bitter taste, dental caries, xerophthalmia, and pain/swelling.

RESULTS

An increase in I-131 doses resulted in a reduction in the UI and %SR and an increase in the combined scintigraphy score. Parotid glands were more affected than submandibular glands. A cumulative dosage of greater than 600 mCi resulted in complete loss of %SR in the parotid glands. No significant difference in either the UI or the %SR was observed between nontreated patients and patients receiving an I-131 dosage of up to 150 mCi. The occurrence of xerostomia was significantly correlated with the gland scintigraphic score, the number of treatment cycles, and I-131 dosage. The occurrence of pain and swelling was extremely low and only lasted for a short time.

CONCLUSION

Although the side effects associated with radioiodine treatment were apparent, they were usually small and temporary. Nevertheless, more consideration should be placed on careful dosing of I-131.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Thyroid cancer: radiation safety precautions in 131I therapy based on actual biokinetic measurements

PURPOSE

To formulate radiation precautions for patients with thyroid cancer who are undergoing thyroid hormone withdrawal-induced hypothyroidism and iodine 131 ((131)I) therapy through actual biokinetic measurements.

MATERIALS AND METHODS

Informed consent and institutional review board approval were obtained. From October 2008 to December 2011, consecutive patients with differentiated thyroid cancer who had been prepared for (131)I ablation treatment or (131)I treatment for metastatic disease during follow-up were prospectively recruited. Calculations based on deduced whole-body retention and measured iodine biokinetics in thyroidal tissue were derived to determine the thyroidal and extrathyroidal compartment uptake fractions and effective half-lives. Precaution times necessary to avoid close contact with family members and the general public were derived from these parameters and regulatory dose limits.

RESULTS

Seventy-seven patients (36 with ablation treatments, 41 with follow-up treatments) were eligible for the analysis. Actual dose rates from patients after therapeutic (131)I administration were greatly lower than those described in the American Thyroid Association (ATA) and Nuclear Regulatory Commission (NRC) models: The mean initial dose rate at 0.3 m for patients with ablation treatment was only 28% (0.183/0.655 µSv/h/MBq) ± 2.9 (standard deviation) (range, 12.1%-38.3%) and 36% (0.183/0.511 µSv/h/MBq) ± 3.7 (range, 15.5%-49.1%) of that described in the NRC and ATA models, respectively; the equivalent values for patients with follow-up treatment were only 30% (0.195/0.655 µSv/h/MBq) ± 3.5 (range, 12.5%-45.3%) and 38% (0.195/0.511 µSv/h/MBq) ± 4.5 (range, 16.0%-58.1%), respectively. The actual mean effective (131)I half-life in the thyroid remnant tissue was greatly lower than that described in the ATA and NRC models: 47.6 versus 175.2 hours.

CONCLUSION

On the basis of the current dose limits, typically administered activities of 3.7 GBq to a patient with ablation treatment or 7.4 GBq to a patient with follow-up treatment required 3 days of sleeping apart for keeping the doses to pregnant women and children below 1 mSv. No precautions were required for non-cosleeping nonpregnant adult family members.

Prediction of risk for symptomatic sialadenitis by post-therapeutic dual (131)I scintigraphy in patients with differentiated thyroid cancer

OBJECTIVE

The aim of this study is to predict the risk of symptomatic sialadenitis after (131)I therapy using the early (third day post-therapy) and delayed (fifth or sixth day post-therapy) post-therapeutic (131)I scintigraphy images in patients with differentiated thyroid cancer (DTC).

METHODS

Included in the study were 112 patients with DTC who underwent early and delayed (131)I scans after (131)I treatment. All patients had normal salivary gland function on salivary scintigraphy performed in the week before the (131)I treatment. Scintigraphy images were visually analyzed and the salivary gland-to-background uptake ratio (SUR) and percent change of the SUR between early and delayed scans were calculated. Calculation of effective half-life and absorbed dose in the salivary glands was performed based on the MIRD schema.

RESULTS

Of 112 patients, symptomatic sialadenitis was diagnosed in 46 patients (41 %). Of these 46 patients, 83 % (38 patients) had persistent (131)I uptake in the salivary glands on both early and delayed scans. Among 55 patients with persistent (131)I uptake in the salivary glands, 69 % experienced symptomatic sialadenitis, while only 14 % of the other 57 patients experienced symptomatic sialadenitis (p < 0.0001). On the early (131)I scintigraphy, SURs of bilateral parotid glands on early scan in patients with symptomatic sialadenitis were significantly higher than in other patients (p = 0.001 for right and p = 0.004 for left). Further, patients with symptomatic sialadenitis had a higher decreasing rate of the SUR and shorter effective half-life of (131)I in bilateral parotid glands than other patients. Using visual analysis and SURs of right and left parotid glands on early (131)I scan as parameters, the sensitivities for predicting symptomatic sialadenitis were 83, 80, and 93 %, respectively. The mean values of effective half-life and absorbed dose in the parotid and submandibular glands were 20.8 ± 6.3 h and 2.7 ± 0.8 Gy, and 22.1 ± 7.9 h and 2.8 ± 1.1 Gy, respectively.

CONCLUSIONS

Symptomatic sialadenitis can be predicted by post-therapeutic (131)I scintigraphy with high sensitivity. Post-therapeutic (131)I scintigraphy could provide effective information on the risk of symptomatic sialadenitis in DTC patients who underwent (131)I treatment.

Modulation of sodium/iodide symporter expression in the salivary gland

BACKGROUND

Physiologic iodide-uptake, mediated by the sodium/iodide symporter (NIS), in the salivary gland confers its susceptibility to radioactive iodine-induced damage following (131)I treatment of thyroid cancer. Subsequent quality of life for thyroid cancer survivors can be decreased due to recurrent sialoadenitis and persistent xerostomia. NIS expression at the three principal salivary duct components in various pathological conditions was examined to better our understanding of NIS modulation in the salivary gland.

METHODS

NIS expression was evaluated by immunohistochemistry in human salivary gland tissue microarrays constructed of normal, inflamed, and neoplastic salivary tissue cores. Cumulative (123)I radioactivity reflecting the combination of NIS activity with clearance of saliva secretion in submandibular and parotid salivary glands was evaluated by single-photon emission computed tomography/computed tomography imaging 24 hours after (123)I administration in 50 thyroid cancer patients.

RESULTS

NIS is highly expressed in the basolateral membranes of the majority of striated ducts, yet weakly expressed in few intercalated and excretory duct cells. The ratio of (123)I accumulation between parotid and submandibular glands is 2.38±0.19. However, the corresponding ratio of (123)I accumulation normalized by volume of interest is 1.19±0.06. The percentage of NIS-positive striated duct cells in submandibular salivary glands was statistically greater than in parotid salivary glands, suggesting a higher clearance rate of saliva secretion in submandibular salivary glands. NIS expression in striated ducts was heterogeneously decreased or absent in sialoadenitis. Most ductal salivary gland tumors did not express NIS. However, Warthin's tumors of striated duct origin exhibited consistent and intense NIS staining, corresponding with radioactive iodine uptake.

CONCLUSIONS

NIS expression is tightly modulated during the transition of intercalated to striated ducts and striated to excretory ducts in salivary ductal cells. NIS expression in salivary glands is decreased during inflammation and tumor formation. Further investigation may identify molecular targets and/or pharmacologic agents that allow selective inhibition of NIS expression/activity in salivary glands during radioactive iodine treatment.