Prediction of late (24-hour) radioactive iodine uptake using early (3-hour) uptake values in Japanese patients with Graves' disease

Real-time quantitation of thyroidal radioiodine uptake in thyroid disease with monitoring by a collar detection device

Radioactive iodine (RAI) is safe and effective in most patients with hyperthyroidism but not all individuals are cured by the first dose, and most develop post-RAI hypothyroidism. Postoperative RAI therapy for remnant ablation is successful in 80–90% of thyroid cancer patients and sometimes induces remission of nonresectable cervical and/or distant metastatic disease but the effective tumor dose is usually not precisely known and must be moderated to avoid short- and long-term adverse effects on other tissues. The Collar Therapy Indicator (COTI) is a radiation detection device embedded in a cloth collar secured around the patient’s neck and connected to a recording and data transmission box. In previously published experience, the data can be collected at multiple time points, reflecting local cervical RAI exposure and correlating well with conventional methods. We evaluated the real-time uptake of RAI in patients with hyperthyroid Graves’ disease and thyroid cancer. We performed a pilot feasibility prospective study. Data were analyzed using R^© (version 4.0.3, The R Foundation for Statistical Computing, 2020), and Python (version 3.6, Matplotlib version 3.0.3). The COTI was able to provide a quantitative temporal pattern of uptake within the thyroid in persons with Graves’ disease and lateralized the remnant tissue in persons with thyroid cancer. The study has demonstrated that the portable collar radiation detection device outside of a healthcare facility is accurate and feasible for use after administration of RAI for diagnostic studies and therapy to provide a complete collection of fractional target radioactivity data compared to that traditionally acquired with clinic-based measurements at one or two time-points.

Clinical Trials Registration NCT03517579, DOR 5/7/2018.

Long-Term Outcomes of Radioiodine Therapy for Juvenile Graves Disease with Emphasis on Subsequently Detected Thyroid Nodules: A Single Institution Experience from Japan

OBJECTIVE

To investigate the long-term outcomes of radioiodine therapy (RIT) for juvenile Graves disease (GD) and the ultrasonographic changes of the thyroid gland.

METHODS

All of 117 juvenile patients (25 males and 92 females, aged 10 to 18 [median 16] years) who had undergone RIT for GD at our clinic between 1999 and 2018 were retrospectively reviewed. Each RIT session was delivered on an outpatient basis. The maximum 131I dose per treatment was 13.0 mCi, and the total 131I dose per patient was 3.6 to 29.8 mCi (median, 13.0 mCi). 131I administration was performed once in 89 patients, twice in 26, and three times in 2 patients. Ultrasonography of the thyroid gland was regularly performed after RIT. The duration of follow-up after the initial RIT ranged from 4 to 226 (median 95) months.

RESULTS

At the latest follow-up more than 12 months after RIT (n = 111), the patients' thyroid functions were overt hypothyroidism (91%), subclinical hypothyroidism (2%), normal (5%), or subclinical hyperthyroidism (2%). New thyroid nodules were detected in 9 patients, 4 to 17 years after initial RIT. Patients with newly detected thyroid nodules underwent RIT with lower doses of 131I and had larger residual thyroid volumes than those without nodules. None of the patients were diagnosed with thyroid cancer or other malignancies during the follow-up period.

CONCLUSION

Over a median follow-up period of 95 months (range, 4 to 226 months), RIT was found to be effective and safe in juvenile GD. However, cumulative evidence from further studies is required to confirm the long-term safety of RIT for juvenile GD.

ABBREVIATIONS

ATD = antithyroid drug; GD = Graves disease; KI = potassium iodide; LT4 = levothyroxine; MMI = methimazole; PTU = propylthiouracil; RAIU = radio-active iodine uptake; RIT = radioiodine therapy; 99mTc = technetium-99m; TSH = thyrotropin.

Analysis of risk factors of rapid thyroidal radioiodine-131 turnover in Graves' disease patients

Rapid iodine-131(¹³¹I) turnover in the thyroid gland is an important feature of Graves’ disease (GD) and also a strong predictor of radioiodine therapy failure. The aim of this study was to explore the predictors of rapid ¹³¹I turnover. The clinical data on 2543 patients were retrospectively reviewed. Patients were divided into 2 groups depending on present or absent with rapid ¹³¹I turnover defined as a 4-hour to 24-hour ¹³¹I uptake ratio of ≥1. Overall, 590 cases (23.2%) had a rapid ¹³¹I turnover. In the univariate analysis, gender, age, FT₃/FT₄ concentration, disease duration, with or without antithyroid drugs (ATD), time of ATD, thyroid weight and thyroid textures displayed significant differences. Cutoff values of age, FT₃ and thyroid weight to predict rapid ¹³¹I turnover were 38 years, 35 pmol/l and 56 g by receiver operating characteristic curves. Binary logistic regression analysis further revealed higher probability of rapid ¹³¹I turnover in patients with thyroid weight ≥56 g (odds ratio [OR]:3.7, 95% confidence interval [CI]: 3.032–4.559), age <38 years (OR:2.3, 95%CI: 1.906–2.856), FT₃ concentration ≥35 pmol/l (OR:7.6, 95%CI: 5.857–8.563) and females (OR:2.2, 95%CI: 1.757–2.791). In conclusion, larger goiters, younger age, higher FT₃ concentration and females are independently associated with rapid ¹³¹I turnover in GD patients.

Calculation of therapeutic activity of radioiodine in Graves' disease by means of Marinelli's formula, using technetium (99mTc) scintigraphy

The therapeutic activity of ¹³¹I administered to patients with Graves' disease can be calculated by means of Marinelli's formula. The thyroidal iodine uptake (¹³¹IU_max) needed for the calculation is usually determined with the use of ¹³¹I. The purpose of the paper was to estimate ¹³¹IU_max on the basis of technetium uptake in the thyroid at 20 min (^99mTcU_20min). Eighty patients suffering from Graves' disease were qualified for radioiodine therapy with measurement of fT₄, fT₃, thyroid-stimulating hormone and its receptor (TRAb). Prior to the treatment, all the patients were euthyroid. ¹³¹IU_max for each patient was determined according to the levels of ¹³¹I after 24 h (¹³¹IU_24h), while effective half-life (T _eff) according to the measurements of ¹³¹IU_24h and ¹³¹I uptake after 48 h (¹³¹IU_48h). Additionally, on the day before measuring ¹³¹IU_24h, ^99mTcU_20min was calculated for each patient. It was demonstrated that there existed a correlation, with statistical significance at p < 0.05, between the following pairs of values: TRAb and ¹³¹IU_24h, TRAb and ^99mTcU_20min, and ^99mTcU_20min and ¹³¹IU_24h. The interdependence between ¹³¹IU_24h and ^99mTcU_20min at the level of significance p < 0.05 is described by the following algorithms: ¹³¹IU_24h = 17.72 × ln (^99mTcU_20min) + 30.485, if TRAb < 10 IU/ml, and ¹³¹IU_24h = 18.03 × ln (^99mTcU_20min) + 38.726, if TRAb > 10 IU/ml. It is possible to predict thyroid iodine uptake ¹³¹IU_24h in Graves' disease on the basis of measuring the uptake of ^99mTcU_20min. This shortens the time necessary for diagnosis and enables the calculation of ¹³¹I activity using Marinelli's formula.

Differentiation between Graves' disease and painless thyroiditis by diffusion-weighted imaging, thyroid iodine uptake, thyroid scintigraphy and serum parameters

The aim of the present study was to assess the apparent diffusion coefficient (ADC) in diffusion-weighted imaging (DWI), thyroid radioactive iodine uptake (RAIU), thyroid scintigraphy and thyrotropin receptor antibody (TRAb) levels in the differential diagnosis between Graves' disease (GD) and painless thyroiditis (PT). A total of 102 patients with GD and 37 patients with PT were enrolled in the study. DWI was obtained with a 3.0-T magnetic resonance scanner, and ADC values were calculated. RAIU and thyroid scintigraphy were performed. Tissue samples were obtained from patients with GD (6 cases) following thyroidectomy, and from patients with PT (2 cases) following biopsy. Receiver operating characteristic (ROC) curves were drawn, optimal cut-off values were selected, and the sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) were assessed. It was found that the ADC, TRAb and RAIU were significantly higher in GD than in PT (P<0.05). ROC curves showed areas under the curves for RAIU, ADC and TRAb that were >0.900. RAIU was the reference method. Sensitivity, specificity, accuracy, PPV and NPV were 96.078, 91.892, 95.000, 97.059 and 89.474% for ADC, and 88.235, 75.676, 84.892, 90.909 and 70.000% for TRAb, after the optimal thresholds of 1.837×10^-3 mm²/sec and 1.350 IU/ml were determined respectively. Histopathology showed that tissue cellularity in PT was much higher than in GD due to massive lymphocytic infiltration. The results of the present study indicate that RAIU, ADC and TRAb are of diagnostic value for differentiating between GD and PT. DWI has great potential for thyroid pathophysiological imaging because it reflects differences in tissue cellularity between GD and PT.

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.