2021 Asia-Pacific Graves' Disease Consortium Survey of Clinical Practice Patterns in the Management of Graves' Disease.

AIM: Although Graves' disease (GD) is common in endocrine practices worldwide, global differences in diagnosis and management remain. We sought to assess the current practices for GD in countries across Asia and the Pacific (APAC), and to compare these with previously published surveys from North America and Europe. METHODS: A web-based survey on GD management was conducted on practicing clinicians. Responses from 542 clinicians were received and subsequently analysed and compared to outcomes from similar surveys from other regions. RESULTS: A total of 542 respondents participated in the survey, 515 (95%) of whom completed all sections. Of these, 86% were medical specialists, 11% surgeons, and 3% nuclear medicine physicians. In addition to serum thyroid-stimulating hormone (TSH) and free thyroxine assays, most respondents would request TSH-receptor autoantibody (TRAb) measurement (68%) during initial work-up. Thyroid ultrasound is requested by about half of respondents (53%), while the use of nuclear medicine scans is limited. The preferred first-line treatment is anti-thyroid drug (ATD) therapy (79%) with methimazole (MMI) or carbimazole (CBZ), followed by radioiodine (RAI; 19%) and surgery (2%). In case of surgery, one-third of respondents would opt for a subtotal rather than a total thyroidectomy. In case of mild Graves orbitopathy (GO), ATDs (67%) remains the preferred treatment, but a larger proportion of clinicians prefer surgery (20%). For a patient with intention to conceive, the preferred treatment pattern remained unchanged, although propylthiouracil (PTU) became the preferred ATD-agent during the first trimester. In comparison to European and American practices, marked differences were noted in the relatively infrequent usage of nuclear medicine scans and the overall higher use of a ATDs and ß-blockers and adjunctive ATD-treatment during RAI in the APAC-group. CONCLUSION: Although regional differences regarding the diagnosis and management of GD are apparent in this first pan-Asia-Pacific survey, this study reveals the overall approach to the management of this disease in Asia-Pacific generally tends to fall between the trends appreciated in the American and European cohorts.

Brain laterality evaluated by F-18 fluorodeoxyglucose positron emission computed tomography in autism spectrum disorders.

Background and rationale: Autism spectrum disorder (ASD) is a neuropsychiatric disorder that has no curative treatment. Little is known about the brain laterality in patients with ASD. F-18 fluorodeoxyglucose positron emission computed tomography (F-18 FDG PET/CT) is a neuroimaging technique that is suitable for ASD owing to its ability to detect whole brain functional abnormalities in a short time and is feasible in ASD patients. The purpose of this study was to evaluate brain laterality using F-18 FDG PET/CT in patients with high-functioning ASD. Materials and methods: This case-control study recruited eight ASD patients who met the DSM-5 criteria, the recorded data of eight controls matched for age, sex, and handedness were also enrolled. The resting state of brain glucose metabolism in the regions of interest (ROIs) was analyzed using the Q.Brain software. Brain glucose metabolism and laterality index in each ROI of ASD patients were compared with those of the controls. The pattern of brain metabolism was analyzed using visual analysis and is reported in the data description. Results: The ASD group's overall brain glucose metabolism was lower than that of the control group in both the left and right hemispheres, with mean differences of 1.54 and 1.21, respectively. We found statistically lower mean glucose metabolism for ASD patients than controls in the left prefrontal lateral (Z = 1.96, p = 0.049). The left laterality index was found in nine ROIs for ASD and 11 ROIs for the control. The left laterality index in the ASD group was significantly lower than that in the control group in the prefrontal lateral (Z = 2.52, p = 0.012), precuneus (Z = 2.10, p = 0.036), and parietal inferior (Z = 1.96, p = 0.049) regions. Conclusion: Individuals with ASD have lower brain glucose metabolism than control. In addition, the number of ROIs for left laterality index in the ASD group was lower than control. Left laterality defects may be one of the causes of ASD. This knowledge can be useful in the treatment of ASD by increasing the left-brain metabolism. This trial was registered in the Thai Clinical Trials Registry (TCTR20210705005).

Riceberry rice (Oryza sativa L.) slows gastric emptying and improves the postprandial glycaemic response.

Postprandial glycaemia is a key determinant of overall glycaemic control. One mechanism by which dietary strategies can reduce postprandial glycaemic excursions is by slowing gastric emptying. This study aimed to evaluate the acute effect of ingesting riceberry rice (RR) compared with that of ingesting white rice (WR) on gastric emptying rate (GER), plasma glucose and glucose-regulating hormones, including insulin, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1), in healthy subjects. A randomised, open-label, within-subject, crossover study was performed in six healthy men. GER was measured by scintigraphy over 240 min, and plasma concentrations of glucose, insulin, GLP-1 and GIP were measured at multiple time points over 180 min. This study revealed that RR slows GER with a reduction in postprandial plasma glucose concentrations compared with WR. Plasma insulin and GLP-1 concentrations did not differ between RR and WR. However, plasma GIP concentrations were markedly increased after WR ingesting v. after RR ingestion. We conclude that RR attenuates postprandial glycaemia by slowing GER without altering plasma insulin or GLP-1. Plasma GIP concentrations are likely related to differences in GER and carbohydrate absorption. We propose that dietary fibre-enriched foods, including RR, could contribute to improvement in postprandial glycaemia via delayed gastric emptying.

Thai National Guideline for Nuclear Medicine Investigations in Epilepsy.

Epilepsy is a disorder of the brain, which is characterized by recurrent epileptic seizures. These patients are generally treated with antiepileptic drugs. However, more than 30% of the patients become medically intractable and undergo a series of investigations to define candidates for epilepsy surgery. Nuclear Medicine studies using Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) radiopharmaceuticals are among the investigations used for this purpose. Since available guidelines for the investigation of surgical candidates are not up-to-date, The Nuclear Medicine Society of Thailand, The Neurological Society of Thailand, The Royal College of Neurological Surgeons of Thailand, and The Thai Medical Physicist Society has collaborated to develop this Thai national guideline for Nuclear Medicine study in epilepsy. The guideline focuses on the use of brain perfusion SPECT and F-18 fluorodeoxyglucose PET (FDG-PET), the mainly used methods in day-to-day practice. This guideline aims for effective use of Nuclear Medicine investigations by referring physicians e.g. epileptologists and neurologists, radiologists, nuclear medicine physicians, medical physicists, nuclear medicine technologists and technicians.

Optimal FDG PET/CT volumetric parameters for risk stratification in patients with locally advanced non-small cell lung cancer: results from the ACRIN 6668/RTOG 0235 trial.

PURPOSE: In recent years, multiple studies have demonstrated the value of volumetric FDG-PET/CT parameters as independent prognostic factors in patients with non-small cell lung cancer (NSCLC). We aimed to determine the optimal cut-off points of pretreatment volumetric FDG-PET/CT parameters in predicting overall survival (OS) in patients with locally advanced NSCLC and to recommend imaging biomarkers appropriate for routine clinical applications. METHODS: Patients with inoperable stage IIB/III NSCLC enrolled in ACRIN 6668/RTOG 0235 were included. Pretreatment FDG-PET scans were quantified using semiautomatic adaptive contrast-oriented thresholding and local-background partial-volume-effect-correction algorithms. For each patient, the following indices were measured: metabolic tumor volume (MTV), total lesion glycolysis (TLG), SUVmax, SUVmean, partial-volume-corrected TLG (pvcTLG), and pvcSUVmean for the whole-body, primary tumor, and regional lymph nodes. The association between each index and patient outcome was assessed using Cox proportional hazards regression. Optimal cut-off points were estimated using recursive binary partitioning in a conditional inference framework and used in Kaplan-Meier curves with log-rank testing. The discriminatory ability of each index was examined using time-dependent receiver operating characteristic (ROC) curves and corresponding area under the curve (AUC(t)). RESULTS: The study included 196 patients. Pretreatment whole-body and primary tumor MTV, TLG, and pvcTLG were independently prognostic of OS. Optimal cut-off points were 175.0, 270.9, and 35.5 cm3 for whole-body TLG, pvcTLG, and MTV, and were 168.2, 239.8, and 17.4 cm3 for primary tumor TLG, pvcTLG, and MTV, respectively. In time-dependent ROC analysis, AUC(t) for MTV and TLG were uniformly higher than that of SUV measures over all time points. Primary tumor and whole-body parameters demonstrated similar patterns of separation for those patients above versus below the optimal cut-off points in Kaplan-Meier curves and in time-dependent ROC analysis. CONCLUSION: We demonstrated that pretreatment whole-body and primary tumor volumetric FDG-PET/CT parameters, including MTV, TLG, and pvcTLG, are strongly prognostic for OS in patients with locally advanced NSCLC, and have similar discriminatory ability. Therefore, we believe that, after validation in future trials, the derived optimal cut-off points for primary tumor volumetric FDG-PET/CT parameters, or their more refined versions, could be incorporated into routine clinical practice, and may provide more accurate prognostication and staging based on tumor metabolic features.

An update on the role of PET/CT and PET/MRI in ovarian cancer.

This review article summarizes the role of PET/CT and PET/MRI in ovarian cancer. With regard to the diagnosis of ovarian cancer, the presence of FDG uptake within the ovary of a postmenopausal woman raises the concern for ovarian cancer. Multiple studies show that FDG PET/CT can detect lymph node and distant metastasis in ovarian cancer with high accuracy and may, therefore, alter the management to obtain better clinical outcomes. Although PET/CT staging is superior for N and M staging of ovarian cancer, its role is limited for T staging. Additionally, FDG PET/CT is of great benefit in evaluating treatment response and has prognostic value in patients with ovarian cancer. FDG PET/CT also has value to detect recurrent disease, particularly in patients with elevated serum CA-125 levels and negative or inconclusive conventional imaging test results. PET/MRI may beneficial for tumor staging because MRI has higher soft tissue contrast and no ionizing radiation exposure compared to CT. Some non-FDG PET radiotracers such as 18F-fluorothymidine (FLT) or 11C-methionine (MET) have been studied in preclinical and clinical studies as well and may play a role in the evaluation of patients with ovarian cancer.

Factors Influencing the Success of the First Radioiodine Therapy for Differentiated Thyroid Carcinoma.

Objective: Differentiated thyroid cancer (DTC) has a favorable prognosis following treatment by thyroidectomy and subsequent post-operative radioactive iodine therapy (RAIT). However, prognostic factors for the success of the first RAIT remain inconclusive. The aim of the present study was to evaluate prognostic factors for the success of the first RAIT in DTC patients. Material and Method: We retrospectively studied 401 DTC patients who underwent total, near-total and subtotal thyroidectomy followed by high dose RAIT from 1994 to 2004. Successful RAIT was assessed using the following criteria: (a) stimulated serum thyroglobulin (sTg) < 10 ng/ml; (b) negative diagnostic 131I total body scan (DxTBS); and (c) no serial increase in thyroglobulin antibody (TgAb) levels. Factors influencing successful first RAIT were evaluated. Results: In total, 401 patients were enrolled into the present study. Most patients were female (81.5%) and had papillary cell type cancer (74.3%). Median tumor size was 2.55 cm. (range, 0­11 cm). Metastases at cervical node and distant sites were found prior to RAIT in 167 and 26 patients, respectively. The first RAIT doses of 2.96­3.7, 5.5 and 7.4 GBq were administered to 133, 262 and 6 patients, respectively. Overall success rate of the first RAIT was 32.9%. From univariate analysis, female sex, age of <45 years, underwent thyroidectomy without cervical lymph node dissection, no multifocality, free surgical margin, no metastasis and sTg of <20 ng/dl at ablation were prognostic factors. Age of <45 years and sTg of <20 ng/dl at ablation were independent significant prognostic factors (both p<0.001) from multivariate analysis. Conclusion: Age below 45 years and sTg below 20 ng/dl at ablation are independent prognostic factors for the success of the first RAIT.

Update of the role of PET/CT and PET/MRI in the management of patients with cervical cancer.

In cervical cancer (CC), fluorine18-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) has been proven to be beneficial for patient management. Positron emission tomography/CT is useful in pretreatment evaluation due to the ability to evaluate disease extent and to assess regional lymph nodes as well as distant sites for metastases. Positron emission tomography/CT has an impact on treatment planning as well as it is incorporated in radiation therapy planning, resulting in more appropriate and effective treatment with less cost and radiation dose to normal tissues. Positron emission tomography/CT is used to predict early treatment response and to assess treatment response after completion of concurrent chemoradiation therapy. Positron emission tomography/CT has been used for surveillance after treatment as well as for restaging in suspected recurrent or metastatic disease. Qualitative PET/CT imaging findings as well as quantitative parameters such as maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) are useful to predict prognosis and clinical outcome. Moreover, PET imaging using other radiotracers to detect and quantify hypoxia may help to identify aggressive tumors and predict treatment outcome even though it is not widely clinical used. Positron emission tomography/magnetic resonance imaging (PET/MRI) instruments are now available, which may potentially improve evaluation of primary tumors and metastatic sites given the improved soft tissue contrast resolution of MRI relative to CT. This article reviews the role of 18F-FDG PET/CT, hypoxia agent PET/CT, and 18F-FDG PET/MRI in the management of patients with CC.

The role of PET/CT as a prognosticator and outcome predictor in lung cancer.

Positron emission tomography/computed tomography (PET/CT) is an important imaging tool for management of lung cancer and can be utilized in diagnosis, staging, restaging, treatment planning and evaluating treatment response. In the past decade PET/CT has proven to be beneficial for the prediction of prognosis and outcome. PET findings before and after treatment, the quantitative PET parameters such as standardized uptake value (SUV), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) as well as delayed PET/CT imaging can be used to determine patient prognosis and outcome. Other tracers such as hypoxia and proliferation marker tracers may be used for prognostication. The prognostic factors derived from PET/CT imaging help early development of risk-adapted treatment strategies, which provides cost-effective treatment and leads to improved patient management. Here, we discuss findings of studies related to application of PET/CT in lung cancer as well as some technical updates on quantitative PET/CT in lung cancer.

Application of partial volume effect correction and 4D PET in the quantification of FDG avid lung lesions.

PURPOSE: The aim of this study is to assess a software-based method with semiautomated correction for partial volume effect (PVE) to quantify the metabolic activity of pulmonary malignancies in patients who underwent non-gated and respiratory-gated 2-deoxy-2-[(18)F]fluoro-D-glucose (FDG)-positron emission tomography (PET)/x-ray computed tomography(CT). PROCEDURES: The study included 106 lesions of 55 lung cancer patients who underwent respiratory-gated FDG-PET/CT for radiation therapy treatment planning. Volumetric PET/CT parameters were determined by using 4D PET/CT and non-gated PET/CT images. We used a semiautomated program employing an adaptive contrast-oriented thresholding algorithm for lesion delineation as well as a lesion-based partial volume effect correction algorithm. We compared respiratory-gated parameters with non-gated parameters by using pairwise comparison and interclass correlation coefficient assessment. In a multivariable regression analysis, we also examined factors, which can affect quantification accuracy, including the size of lesion and the location of tumor. RESULTS: This study showed that quantification of volumetric parameters of 4D PET/CT images using an adaptive contrast-oriented thresholding algorithm and 3D lesion-based partial volume correction is feasible. We observed slight increase in FDG uptake by using PET/CT volumetric parameters in comparison of highest respiratory-gated values with non-gated values. After correction for partial volume effect, the mean standardized uptake value (SUVmean) and total lesion glycolysis (TLG) increased substantially (p value <0.001). However, we did not observe a clinically significant difference between partial volume corrected parameters of respiratory-gated and non-gated PET/CT scans. Regression analysis showed that tumor volume was the main predictor of quantification inaccuracy caused by partial volume effect. CONCLUSIONS: Based on this study, assessment of volumetric PET/CT parameters and partial volume effect correction for accurate quantification of lung malignant lesions by using respiratory non-gated PET images are feasible and it is comparable to gated measurements. Partial volume correction increased both the respiratory-gated and non-gated values significantly and appears to be the dominant source of quantification error of lung lesions.

The value of ¹8F-FDG PET/CT in the management of malignant peripheral nerve sheath tumors.

PURPOSE: Our objective was to determine how positron emission tomography (PET)/CT had been used in the clinical treatment of malignant peripheral nerve sheath tumor (MPNST) patients at The University of Texas MD Anderson Cancer Center. METHODS: We reviewed a database of MPNST patients referred to MD Anderson Cancer Center during 1995-2011. We enrolled 47 patients who underwent PET/CT imaging. Disease stage was based on conventional imaging and PET/CT findings using National Comprehensive Cancer Network (NCCN) guidelines. Treatment strategies based on PET/CT and conventional imaging were determined by chart review. The maximum and mean standardized uptake values (SUVmax, SUVmean), metabolic tumor volume (MTV), total lesion glycolysis (TLG), change in SUVmax, change in MTV, and change in TLG were calculated from the PET/CT studies before and after treatment. Response prediction was based on imaging studies performed before and after therapy and categorized as positive or negative for residual tumor. Clinical outcome was determined from chart review. RESULTS: PET/CT was performed for staging in 16 patients, for restaging in 29 patients, and for surveillance in 2 patients. Of the patients, 88 % were correctly staged with PET/CT, whereas 75 % were correctly staged with conventional imaging. The sensitivity to detect local recurrence and distant metastasis at restaging was 100 and 100 % for PET/CT compared to 86 and 83 % for conventional imaging, respectively. PET/CT findings resulted in treatment changes in 31 % (5/16) and 14 % (4/29) of patients at staging and restaging, respectively. Recurrence, MTV, and TLG were prognostic factors for survival, whereas SUVmax and SUVmean were not predictive. For 21 patients who had imaging studies performed both before and after treatment, PET/CT was better at predicting outcome (overall survival, progression-free survival) than conventional imaging. A decreasing SUVmax ≥ 30 % and decrease in TLG and MTV were significant predictors for overall and progression-free survival. CONCLUSION: PET/CT is valuable in MPNST management because of its high accuracy in staging and high sensitivity and accuracy in restaging as well as improvements in treatment planning. MTV from baseline staging studies is predictive of survival. Additionally, change in SUVmax, TLG, and MTV accurately predicted outcomes after treatment.

Impact of initial PET/CT staging in terms of clinical stage, management plan, and prognosis in 592 patients with non-small-cell lung cancer.

PURPOSE: Our objective was to determine the impact of initial (18)F-FDG PET/CT (PET/CT) staging on clinical stage and the management plan and the prognostic value of PET/CT in patients with non-small-cell lung cancer (NSCLC). METHODS: We retrospectively reviewed the records of 592 patients with NSCLC who were referred to The University of Texas MD Anderson Cancer Center during 2002/2011 and had both PET/CT and conventional CT for initial staging. Clinical stages and management plans were compared between PET/CT and CT. The impact of PET/CT on management plans was considered medium/high when PET/CT changed the planned treatment modality or treatment intent. PET/CT and CT stages were compared with all-cause mortality and survival rates. We also assessed potential prognostic factors for progression-free survival (PFS) and overall survival (OS). RESULTS: PET/CT changed the stage in 170 patients (28.7 %; 16.4 % upstaged, 12.3 % downstaged). PET/CT had a medium/high impact on the management plan in 220 patients (37.2 %). PFS and OS were significantly worse in patients with upstaged disease than in patients with no change in stage (median PFS 29.0 vs. 53.8 months, P < 0.001; median OS:64.7 vs. 115.9 months, P = 0.006). PFS and OS were significantly worse in patients with medium/high impact of PET/CT than in patients with no/low impact of PET/CT (median PFS 24.7 vs. 60.6 months, P < 0.001; median OS 64.7 vs. 115.9 months, P < 0.001). In multivariate analysis, a medium/high impact of PET/CT was an independent predictor of worse PFS (hazard ratio, HR, 1.73; 95 % CI 1.30 - 2.29; P = 0.0002) and OS (HR 1.84; 95 % CI 1.26 - 2.69; P = 0.002). CONCLUSION: Initial PET/CT staging not only impacts stage and management plan but also has prognostic value.

Cost-effectiveness analysis of 18F-FDG PET/CT in detecting suspected recurrence or metastasis in well-differentiated thyroid carcinoma patients with negative diagnostic total body scan in Thailand: a decision analysis.

OBJECTIVE: To evaluate cost-effectiveness analysis of 18F-FDG PET/CT to detect tumor recurrence or metastasis in well-differentiated thyroid cancer patients with high Tg but negative TBS in Thailand. MATERIAL AND METHOD: A retrospective literature review of 55 studies published between 1978 and 2010 was done. Decision analysis by TreeAge program showed an evaluation of the most cost-effective treatment and 18F-FDG PET/CT scan in thyroid cancer patients with high Tg but negative TBS. The incremental cost and life years gained associated with seven strategies approached were analyzed by the decision tree model. The first strategy was treatment with empirical high dose 131I therapy. The second to the seventh strategies were using imaging investigations by CT scan of neck and chest, 99mTc MIBI scan, and 18F-FDG PET/CT scan to identify recurrent, persistent, and metastatic lesions before the specific treatment via curative surgery, external radiotherapy, and high dose 131I therapy. All strategies were adopted using hospital perspective and direct medical cost was estimated based on the reference price of Siriraj Hospital. Deterministic sensitivity analysis was conducted to investigate the effect of the cost of PET/CT scan. RESULTS: The strategy using 18F-FDG PET/CT scan to detect recurrence or metastasis and possible curative surgery in operable cases and high dose 131I therapy in inoperable cases gave the highest life years gained of 27.08 with cost of 90,227.61 Baht (2,926.24 US dollars) and acceptable incremental cost effectiveness ratio (ICER) of 6,936.88 Baht (224.98 US dollars) per life year gained when compared to the least costly strategy using 99mTc MIBI scan and additional 18F-FDG PET/CT scan in negative MIBI result. Other strategies were dominated by this PET/CT strategy. Deterministic sensitivity analysis (based on the willingness to pay (WTP) 360,000 Baht (11,675.42 US dollars) showed that the cost of PET/CT scan has no impact on the net health benefit. CONCLUSION: Based on the hospital perspective, the cost-effectiveness of 18F-FDG PET/CT scan in detecting suspected recurrence or metastasis in thyroid carcinoma patients with negative diagnostic TBS but high Tg was first done using 18F-FDG PET/CT scan to identify disease, followed by curative surgery or high dose 131I therapy. Moreover cost of PET/CT scan did not influence the net health benefit. This PET/CT benefit is helpfulfor considering the proper PET/CT use for thyroid cancer in Thailand.

The correlation of post-operative radioiodine uptake and Tc-99m pertechnetate thyroid scintigraphy and the result of thyroid remnant ablation.

OBJECTIVE: Determine the relationship between postoperative thyroid remnant using 24 h radioiodine uptake and Tc-99m pertechnetate scintigraphy, and the success of high dose radioiodine ablation. MATERIAL AND METHOD: Retrospectively enrolled 250 patients with DTC who underwent thyroidectomy and radioiodine ablation. Postoperative Tc-99m pertechnetate and 24 h 1-131 uptake were reviewed to evaluate thyroid remnant and the directly compared with ablation outcome. The successful ablation was defined using negative WBS and stimulated Tg < 10 ng/ml in the absence of TgAb at six to 12 months after treatment. The relationship between success of ablation and other variables were evaluated RESULTS: One hundred twenty four patients (49.6%) were successfully ablated after single high dose radioiodine ablation. The authors found no association with age, sex, extent of surgery, tumor histology, tumor size, mutifocal, extrathyroidal invasion, 1-131 administered dose, interval from surgery to radioiodine ablation, Tc-99m pertechnetate scan, or 24 h 1-131 uptake, and successful ablation. The initial Tg level was the only variable found to be associated with success (p < 0.001). CONCLUSION: Neither Tc-99m pertechnetate thyroid scintigraphy nor 24 h 1-131 uptake percentage in the evaluation of postsurgical thyroid remnant can predict radioiodine ablation outcome in patients with DTC. Serum Tg level at the time of ablation could be a reasonable predictor of the success of ablation.

A prospective randomized study of the efficacy and cost-effectiveness of high and low dose regimens of I-131 treatment in hyperthyroidism.

OBJECTIVE: To compare the efficacy and cost-effectiveness of high and low dose regimens of I-131 treatment in patients with hyperthyroidism. MATERIAL AND METHOD: One hundred fifty patients with proven hyperthyroidism were randomly allocated into the high (74 patients) and low (76 patients) dose regimen of I-131 treatment. Four patients of the high dose group and one patient of the low dose group were excluded because of lost follow-up. A gland-specific dosage was calculated on the estimated weight of thyroid gland and 24-hour I-131 uptake. The high and low I-131 dose regimens were 150 microCi/gm and 100 microCi/gm, respectively. The first mean radioiodine activity administered to the high and low dose group was 10.2 and 8 mCi, respectively. Repeated treatment was given to 25 patients of the high dose group and 40 patients of the low dose group. Clinical outcome and calculated costs for outpatient attendances, and laboratory tests together with initial and subsequent treatments were evaluated for one year after I-131 treatment. Elimination of hyperthyroidism that resulted in either euthyroidism or hypothyroidism was classified as therapeutic success. The cost effectiveness was also compared. RESULTS: At 6 months after treatment, 45 (64.3%) patients receiving high dose and 59 (78.7%) patients receiving low dose were hyperthyroidism. Clinical outcome at one year showed persistence of hyperthyroidism in 21 (30%) patients of the high dose regimen and 36 (48%) patients of the low dose regimen. At one year post treatment, it was demonstrated that the high dose regimen could eliminate hyperthyroidism in a significantly shorter time than the low dose regimen, i.e., 259.6 days and 305.5 days, respectively, p = 0.008). For the persistent hyperthyroid patients, the average total cost of treatment in the low dose group was significantly higher than that of the high dose group, i.e., 13,422.78 baht and 10,942.79 baht, respectively; p = 0.050). CONCLUSION: A high dose regimen of radioactive iodine treatment is more effective than the low dose regimen. The successful outcome of a high dose regimen occurred significantly earlier than that of the low dose regimen. For the persistent hyperthyroid patients, the average total cost in the low dose group was significantly higher than that of the high dose group.