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Differentiated thyroid cancer (DTC) is the most common endocrine malignancy. Patients who receive systematic care typically have a better prognosis. RAI treatment plays a key role in eradicating any remaining thyroid lesions in DTC patients, hence decreasing the risk of distant metastases and cancer recurrence. As research continues to advance, RAI treatment is becoming more and more individualized. Because of the excellent prognosis for DTC patients, there is a relatively broad window for RAI treatment, making it easy to overlook when to receive RAI treatment. However, research on this issue can help patients with varying recurrence risk stratification make better decisions about when to begin RAI treatment following surgery, and physicians can schedule patients based on the severity of their disease. This will improve patient prognosis and lessen needless anxiety in addition to helping solve the problems of unjust healthcare resource distribution. In this review, we will mainly discuss the target population of RAI treatment as well as studies that examine the impact of RAI treatment timing on patient outcomes. In an effort to discourage DTC patients and physicians from selecting RAI therapy at random, we also review the possible negative effects of this treatment. [ABSTRACT FROM AUTHOR]

Background: For differentiated thyroid cancer (DTC) patients with thyroglobulin (Tg) elevation and negative iodine scintigraphy (commonly termed "TENIS" syndrome) after thyroidectomy, radioactive iodine (RAI) therapy, and thyroid-stimulating hormone (TSH) suppression therapy, empirical RAI therapy may be considered. However, the outcome data of TENIS syndrome without structural disease after empirical RAI therapy have not shown clear evidence of improvement in survival. We assessed the efficacy of such empirical RAI therapy in TENIS syndrome without structural disease and evaluated the progression-free survival (PFS). Methods: A total of 80 papillary thyroid cancer (PTC) patients with TENIS syndrome without structural disease were included in this retrospective study. 52 patients were treated with empirical RAI therapy while another 28 patients were untreated. The progression-free survival (PFS) of both groups was defined as the main outcome. The secondary outcome was the comparison of serum Tg levels 12 months after being diagnosed as TENIS syndrome. Results: The PFS of the empirical RAI therapy group was better than the untreated group (p < 0.001). Moreover, there was significant difference in Tg normalization between patients treated with empirical therapy and without treatment (p = 0.001). Empirical RAI therapy (p = 0.001) predicts better PFS. Male gender (p = 0.041) and empirical RAI therapy (p = 0.002) predict better remission in serum Tg level. Conclusion: Patients with TENIS syndrome without structural disease can benefit from empirical RAI therapy in both PFS and Tg normalization. [ABSTRACT FROM AUTHOR]

Purpose: The objective of this study is to evaluate the lesion absorbed dose (AD), biological effective dose (BED), and equivalent uniform dose (EUD) to clinical-response relationship in lesional dosimetry for 131I therapy.Methods: Nineteen lesions in four patients with metastatic differentiated thyroid cancer (DTC) were evaluated. The patients underwent PET/CT imaging at 2 h, 24 h, 48 h, 72 h, and 96 h post administration of ~ 33-65 MBq (0.89-1.76 mCi) of 124I before undergoing 131I therapy. The 124I PET/CT images were used to perform dosimetry calculations for 131I therapy. Lesion dose-rate values were calculated using the time-activity data and integrated over the measured time points to obtain AD and BED. The Geant4 toolkit was used to run Monte Carlo on spheres the same size as the lesions to estimate EUD. The lesion AD, BED, and EUD values were correlated with response data (i.e. change in lesion size pre- and post-therapy): complete response (CR, i.e. disappearance of the lesion), partial response (PR, i.e. any decrease in lesion length), stable disease (SD, i.e., no change in length), and progressive disease (PD, i.e., any increase in length).Results: The lesion responses were CR and PR (58%, 11/19 lesions), SD (21%, 4/19), and PD (21%, 4/19). For CR and PR lesions, the ADs, BEDs and EUDs were > 75 Gy for 82% (9/11) and < 75 Gy for 18% (2/11). The ADs and BEDs were < 75 Gy for SD and PD lesions.Conclusion: By performing retrospective dosimetry calculations for 131I therapy based on 124I PET/CT imaging, we evaluated the correlation of three dosimetric quantities to lesional response. When lesion AD, BED, and EUD values were > 75 Gy, 47% (9/19) of the lesions had a CR or PR. The AD, BED, and EUD values for SD and PD lesions were < 75 Gy. The data presented herein suggest that the greater the lesion AD, BED, and/or EUD, the higher the probability of a therapeutic response to 131I therapy. [ABSTRACT FROM AUTHOR]

Objective: The baseline treatment of differentiated thyroid cancer (DTC) consists of thyroidectomy followed by postoperative risk-adapted radioiodine therapy (RAIT) when indicated. The choice of most appropriate RAI activities to administer with the aim to reach an efficient remnant ablation and reduce the risk of recurrence is yet an open issue and the detection of basal factors that may predict treatment response seems fundamental. The aim of this study was to investigate the potential role of Hashimoto thyroiditis (HT) in predicting 1-year and 5-year treatment response after RAIT and prognosis. Methods: We retrospectively included 314 consecutive patients (174 low-risk and 140 intermediate-risk) who received thyroidectomy plus RAIT. One-year and 5-year disease status was evaluated according to 2015 ATA categories response based upon biochemical and structural findings. Results: HT was reported histopathologically in 120 patients (38%). DTC patients with concomitant HT received a higher number of RAITs and cumulative RAI activities. Initial RAIT reached an excellent response in 63% after one year and 84% after 5 years. The rate of excellent response one year and 5-year after first RAIT was significantly lower in HT groups, compared to not HT (p < 0.001). Instead, HT did not have a prognostic role considering PFS and OS; while stimulate thyroglobulin (sTg) at ablation was significantly related to survival. Conclusions: HT may affect the efficacy of RAIT in low to intermediate risk DTC, particularly reducing the successful rate of excellent response after RAIT. Instead, HT did not have a prognostic impact such as stimulated sTg. [ABSTRACT FROM AUTHOR]

Objective: To compare the clinical outcome in patients who received adjuvant therapy with radioactive iodine (RAI) using different preparation methods, namely, thyroid hormone withdrawal (THW) and recombinant human thyroid-stimulating hormone (rhTSH), after undergoing thyroidectomy for intermediate- to high-risk differentiated thyroid carcinoma (DTC) according to the American Thyroid Association criteria. Methods: Between May 2012 and October 2018, 136 patients who underwent adjuvant therapy with high-dose (3700 MBq) RAI for DTC without any metastatic lesions or macroscopic residual lesions after surgical resection were retrospectively selected. Patients were excluded if distant metastasis was confirmed during adjuvant therapy or if the outcome could not be confirmed; thus, 112 patients were finally evaluated. Patients underwent either a 3-week I restriction with thyroxine withdrawal or a 2-week I restriction with rhTSH administration. The serum thyroglobulin (Tg) concentration was measured, and 131I scintigraphy (370 MBq) was performed 6–12 months after adjuvant therapy. The definition of the initial achievement of adjuvant therapy was the disappearance of the uptake of 131I at the thyroid bed and serum Tg concentration < 2.0 ng/mL. The results of the adjuvant therapy between the groups were compared using the Fisher's exact test, and the TSH levels and estimated glomerular filtration rate (eGFR) were compared using the Welch's t test. Results: The THW and rhTSH groups included 47 and 65 patients, respectively, and the intermediate- and high-risk groups included 63 and 49 patients, respectively. No patient was assigned to the low-risk group. In the THW and rhTSH groups, the initial RAI adjuvant therapy goal was achieved in 30/47 (63.8%) and 46/65 patients (70.8%), respectively (p = 0.54); mean ± standard deviation of the TSH levels was 123.8 ± 46.4 µIU/mL and 274.5 ± 97.7 µIU/mL, respectively (p < 0.01), and eGFR (treatment/pre-treatment) was 0.81 and 0.99, respectively (p < 0.01). In the intermediate- and high-risk groups, the initial RAI adjuvant therapy goal was achieved in 43/63 patients (68.3%) and 33/49 (67.3%), respectively (p = 1.0). Conclusion: No significant differences were observed between the preparation methods in the initial achievement of RAI adjuvant therapy. However, patients in the rhTSH group demonstrated higher TSH levels and retained eGFR. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to compare the clinical outcomes of patients who received radioactive iodine (RAI) ablation after undergoing thyroidectomy for intermediate-to-high-risk differentiated thyroid carcinoma (DTC) according to the American Thyroid Association (ATA) criteria.Methods: We retrospectively examined patients who underwent RAI ablation for DTC after surgical resection without macroscopic residual lesions or metastatic lesions between December 2011 and August 2016. Among 147 patients who underwent RAI ablation, those whose initial pathological stages or RAI ablation results were unknown and whose distant metastases were confirmed during RAI ablation were excluded. Low-dose therapy was defined as administration of 1110 MBq of 131iodine (131I), while high-dose therapy referred to administration of 2960-3700 MBq of 131I. We defined initial success of RAI ablation as a serum thyroglobulin concentration of < 2.0 ng/mL without thyroid-stimulating hormone stimulation and disappearance of 131I uptake in the thyroid bed on 131I scintigraphy 6-12 months after RAI ablation. RAI ablation success rates were compared between the low-dose and high-dose groups using Fisher's exact test, and inverse probability of treatment weighting (IPTW) analysis was performed for adjusting potential biases.Results: Among the 119 patients examined in this study (39 men and 80 women), 79 were classified as having intermediate risk, while 40 were classified as having high risk based on the ATA guideline. Initial RAI ablation success was achieved in 50/68 (73.5%) patients from the low-dose group and in 36/51 patients (70.6%) from the high-dose group (p = 0.84). Moreover, IPTW analysis showed no significant difference between the low-dose and high-dose groups. However, the success rate tended to be superior in high-risk patients who received high-dose therapy (86.2%) than in those who received low-dose therapy (72.7%) (p = 0.37).Conclusion: There was no significant difference in the RAI ablation success rate between the low-dose and high-dose groups involving patients with intermediate-to-high-risk DTC. However, high-dose RAI ablation may be recommended in high-risk patients. [ABSTRACT FROM AUTHOR]

Objective: Negative 99mTc-pertechnetate uptake of the thyroid bed indicates the absence or a small volume of remnant thyroid tissue (RTT) after total thyroidectomy (TT). The aim of this study is to evaluate the predictive value of negative 99mTc-pertechnetate scintigraphy for excellent response (ER) to radioactive iodine therapy (RIT) in low- to intermediate-risk differentiated thyroid cancer (DTC) patients.Patients: One-hundred and eighty-nine low- to intermediate-risk DTC patients who underwent TT, RIT with a single dose of 30 mCi and suppressive therapy with thyroid-stimulating hormone (TSH) from July 2015 to February 2016 in our hospital were retrospectively evaluated. 99mTc-pertechnetate thyroid scintigraphy was performed just before RIT and images were reported dichotomously as negative or positive. The response of patients was assessed for 23.2 ± 3.8 months after RIT and dichotomized as excellent response (ER) or non-excellent response (NER). 99mTc-pertechnetate uptake, age at diagnosis, gender, multifocality, T stage, N stage, preablative stimulated thyroglobulin (ps-Tg), and TSH were explored as potential predictors for ER.Results: 80.68% (71/88) of patients with negative 99mTc-pertechnetate uptake achieved ER. When patients were evaluated according to different ps-Tg levels, we found that 94.83% (55/58) of patients with ps-Tg < 1 ng/ml and negative 99mTc-pertechnetate uptake achieved ER. Multivariate Cox regression analysis revealed that ps-Tg (P = 0.0001) and 99mTc-pertechnetate uptake (P = 0.0473) were independent predictors for ER.Conclusions: In addition to ps-Tg, negative 99mTc-pertechnetate uptake is also a significant independent predictor for an excellent response in low- to intermediate-risk patients. It may be possible to omit RIT in patients with ps-Tg < 1 ng/ml and concurrent negative 99mTc-pertechnetate uptake. [ABSTRACT FROM AUTHOR]

Objective: To identify prognostic factors associated with a low-iodine diet (LID) and the amount of remnant thyroid tissue in Japanese patients with differentiated thyroid cancer (DTC) who received initial I-131 remnant ablation (RAI) using a fixed low dose of I-131 (1110 MBq).Patients and Methods: In this prospective study, we enrolled 45 patients. Patients were classified into a self-managed LID group and a strict LID group. We measured the urinary iodine concentration on the day of RAI after patients consumed LID for 2 weeks. Thyroid-stimulating hormone-induced thyroglobulin (Tg) levels and I-131 uptake by the remnant thyroid tissue were also evaluated. A response-evaluation whole-body scan (WBS) was performed 6-8 months after RAI to determine the outcome of the therapy.Results: Post-LID urinary iodine levels of the strict LID group tended to be lower than those of the self-managed LID group. Twenty-five cases (56%) showed absence of uptake, whereas 20 cases (44%) showed residual uptake on the response-evaluation WBS. There were no significant differences between "absence" and "residual" groups in urinary iodine concentrations and Tg levels (p = 0.253 and p = 0.234, respectively). However, significant differences were observed in I-131 uptake by the thyroid bed (p = 0.035).Conclusions: For patients following the current Japanese method of a 2-week LID, the urinary iodine concentration was not a predictive factor for the successful outcome of RAI. In contrast, low I-131 uptake by the thyroid bed, revealed by the scintigram after RAI, may serve as a favorable predictive factor. [ABSTRACT FROM AUTHOR]

Objective: The aim of the study was to evaluate the usefulness of Tc-pertechnetate whole body scan (WBS) with neck and chest SPECT/CT for detection of post-surgical thyroid remnant and metastasis in differentiated thyroid cancer (DTC) patients. Methods: Fifty-six post total thyroidectomy patients were included. All patients were prospectively imaged with Tc-pertechnetate WBS with neck and chest SPECT/CT before I ablation. The post-ablative I WBS with SPECT/CT was performed at 5-7 days after receiving I. Both scans were directly compared to determine the concordance of sites and number of remnant and metastasis. Results: Overall per-patient analysis, the percentage of concordance between two scans was 96.4 %. In thyroid bed, lymph node, lung and bone subgroups, the percentage of concordance between two scans was 96.4, 92.9, 98.2 and 100 %, respectively. All of them show good correlation with unweighted kappa between 0.7 and 1. Overall per-lesion analysis, the percentage of concordance between two scans was 84 %. In thyroid bed, lymph node, lung and bone subgroups, the percentage of concordance between two scans was 89.5, 55, 82.6 and 50 %, respectively. Conclusions: Pre-ablative pertechnetate WBS with neck and chest SPECT/CT has good correlation for the detection of post-surgical thyroid remnant, cervical node and discrete lung nodule metastasis as compared to I WBS with SPECT/CT per-patient basis. Because I therapeutic activity is desired base on metastatic site and less concerning about the number of lesions, pre-ablative Tc-pertechnetate WBS with SPECT/CT was a good alternative tool to avoid radioiodine stunning in post-surgical DTC patients. [ABSTRACT FROM AUTHOR]

Purpose: High-energy (HE) collimators are usually applied for I-131 imaging after ablation treatment of differentiated thyroid cancer (DTC). However, purchase of HE collimators has been avoided in many nuclear medicine departments because the HE collimators are more expensive than other collimators. In this study, we compared the I-131 imaging using HE- and medium-energy (ME) collimators, which is more versatile than HE collimators. Materials and methods: To simulate DTC patients with extra-thyroid beds, a phantom of acrylic containers containing I-131 was used. To simulate patients with thyroid beds, four phantoms representing extra-thyroid beds were arranged around the phantom representing normal thyroid tissues. Patients administered 1.11 or 3.70 GBq NaI-131 were also evaluated. Whole-body imaging and SPECT imaging of the phantoms and patients performed using HE-general-purpose (HEGP) and ME-low-penetration (MELP) collimators, and full-width at half maximum (FWHM) and percent coefficient of variation (%CV) were measured. Results: In the extra-thyroid beds, FWHM and %CV with MELP were negligibly different from those with HEGP in whole-body imaging. Although FWHM with MELP was a little different from that with HEGP in SPECT imaging, %CV with MELP was significantly higher than that with HEGP. In the thyroid beds, only an extra-thyroid bed including higher radioactivity was identified in whole-body imaging with both collimators. Although SPECT images with MELP could not clarify extra-thyroid beds with low radioactivity, HEGP could identify them. In patients, although some whole-body images with MELP could not detect extra-thyroid beds, whole-body imaging with HEGP and SPECT imaging with both collimators could detect them. Conclusions: Although HEGP is the best collimator for I-131 imaging, MELP is applicable for not only whole-body imaging but also SPECT imaging. [ABSTRACT FROM AUTHOR]

We report a 55-year-old man affected by differentiated thyroid carcinoma with lymph nodes metastases. After conventional levothyroxine withdrawal, the patient underwent thyroid remnant ablation by oral administration of radioiodine-131 ablative activity (3700 MBq). 7 days later, post-therapy whole body scan (pWBS) demonstrated thyroid remnant and showed a large area of abnormal radioiodine uptake located in the posterior left upper abdomen. Ultrasonography of the abdominal region revealed a cyst in left kidney corresponding to the focal radioiodine uptake. On the same day, I static images of the posterior upper abdomen obtained before and after administration of furosemide, showed that radioiodine uptake in the lesion was markedly lower after diuretic administration, indicating that radioiodine accumulation in the renal cyst is linked to an active secretory process by the renal tubule. Due to its non-negligible frequency, renal cyst should be taken into account in DTC patients as a potential pitfall at I pWBS. [ABSTRACT FROM AUTHOR]

Objective: The aim of the study was to disclose the place of F-FDG PET/CT to predict recurrent disease in patients with differentiated thyroid cancer (DTC), negative radioiodine whole-body scan (WBS) and high serum thyroglobulin (Tg). Methods: Seventy-one patients who underwent total thyroidectomy followed by radioactive iodine ablation and had negative radioiodine WBS but elevated Tg levels underwent PET/CT. They were followed up for 6-50 months (median 23) for the occurence of recurrent disease as detected by either clinical findings, other imaging modalities or histopathological examination. The place of PET/CT findings at baseline to predict the presence of recurrent disease was evaluated. Correlation between PET/CT findings and Tg levels was examined and a threshold for Tg level above which the predictive value of PET/CT was highest was determined. Results: PET/CT was positive for recurrent disease in 38 (53.5 %) patients. The sensitivity, specificity, PPV, NPV and diagnostic accuracy of PET/CT to predict the occurence of recurrent disease at follow-up were 68.8, 78.3, 86.8, 54.5 and 71.9 %, respectively. The sensitivity, accuracy and PPV of PET/CT increased with increasing Tg levels. The highest diagnostic accuracy of PET/CT, with a sensitivity of 76.2 % and a specificity of 100 % to detect recurrent disease appeared to be at a Tg level greater than 29 ng/mL. Conclusion: Our findings suggest that F-FDG-PET/CT is a valuable tool to predict the occurence of recurrent disease in patients with DTC, negative WBS and elevated Tg levels. PET/CT positivity has been shown to be strongly and positively correlated with Tg levels in this patient subset. [ABSTRACT FROM AUTHOR]

The primary clinical application of F FDG PET/CT (Fluorine labeled flurodeoxyglucose positron emission tomography/computed tomography) in differentiated thyroid carcinoma is in the identification of active disease in thyroglobulin (Tg) positive (>10 ng/ml), whole body iodine scan negative patients. The impact of FDG PET/CT in diagnosis, surveillance, cure, and progression-free survival of differentiated thyroid carcinoma patients remains to be seen. Five main indications of FDG PET/CT in thyroid cancer have been recommended by revised American thyroid association guidelines 2009. This review aims to provide a complete picture of PET imaging in thyroid malignancies and enumerates each indication with literature review. This review also highlights recent advances in targeted molecular imaging. Currently differentiated thyroid cancer is best imaged using conventional single photon emission computed tomography-based radioiodine tracers (I/I). Although the utility of FDG PET in well differentiated thyroid cancer patients who are iodine negative but with raised Tg is well established, evidence is emerging on the advantages of FDG PET/CT in other histological types of thyroid malignancy, such as Hurthle cell, medullary, and the anaplastic malignancies. Novel PET radiotracers, such as Iodine (I), F-DOPA (3,4-dihydroxy- l-phenylalanine), and Ga-DOTA peptides are revolutionizing the way thyroid malignancies are imaged. Newer concepts on targeted molecular imaging and theranostics are ushering in new possibilities for imaging and treating thyroid cancer. [ABSTRACT FROM AUTHOR]

Objective: To investigate predictors for successful ablation and disease-free status after high-dose radioiodine therapy in patients with differentiated thyroid cancer. Methods: We enrolled 173 consecutive patients with differentiated thyroid cancer between November 2001 and December 2004 retrospectively (female 145, 46 ± 12 years). All patients underwent total thyroidectomy and I-131 ablative therapy (IAT) (3.7-5.4 GBq). The success or failure of ablation was assessed 6-9 months after the IAT with reference to undetectable thyroglobulin (Tg) and negative I-131 whole body scan (WBS). Afterward, the decision for disease-free status was evaluated using Tg and WBS (follow-up period after 1st IAT 7-81 months, median 43 months, criteria of disease-free: less than 10 ng/ml TSH-stimulated Tg or less than 2 ng/ml TSH-unstimulated Tg and/or negative WBS). Clinical and tumoral factors such as sex, age, pathologic type, the size of tumor, quantified cervical uptake in WBS1, pattern in WBS1, ablative therapy dose, AJCC stage, lymph node (LN) stage, Tg just before IAT (Tg1), and ablation status were assessed using logistic regression analyses. Results: There were 93 successful ablations (54 %). Significant predictors for the ablation failure were Tg1 (OR = 8.42; 95 % CI = 2.76-25.69; p < 0.0001), LN metastasis (OR = 3.05; 95 % CI = 1.11-8.37; p = 0.031), and quantified cervical uptake in WBS1 (OR = 4.95; 95 % CI = 1.07-22.88; p = 0.041). One hundred fifty-five patients were determined as disease-free after follow-up. All the eighteen patients with persistent disease were identified as ablation failure after first IAT. Significant predictors for the disease-free status were Tg1 (OR = 0.98; 95 % CI = 0.97-0.99; p = 0.028), tumor size (OR = 0.53; 95 % CI = 0.28-0.96; p = 0.044), and quantified cervical uptake in WBS1 (OR = 0.87; 95 % CI = 0.76-0.98; p = 0.024). Conclusions: The thyroglobulin and quantified cervical uptake in whole body scan are significant predictors for the successful ablation and disease-free status after follow-up. [ABSTRACT FROM AUTHOR]

Radioactive iodine (RAI, I) has been used as a therapeutic agent for differentiated thyroid cancer (DTC) with over 50 years of history. Recently, it is now attracting attention in medical fields as one of the molecular targeting therapies, which is known as targeted radionuclide therapy. Radioactive iodine therapy (RIT) for DTC, however, is now at stake in Japan, because Japan is confronting several problems, including the recent occurrence of the Great East Japan Disaster (GEJD) in March 2011. RIT for DTC is strictly limited in Japan and requires hospitalization. Because of strict regulations, severe lack of medical facilities for RIT has become one of the most important medical problems, which results in prolonged waiting time for Japanese patients with DTC, including those with distant metastasis, who wish to receive RIT immediately. This situation is also due to various other factors, such as prolonged economic recession, super-aging society, and subsequent rapidly changing medical environment. In addition, due to the experience of atomic bombings in Hiroshima and Nagasaki, Japanese people have strong feeling of 'radiophobia'. There is fear that GEJD and related radiation contamination may worsen this feeling, which might be reflected in more severe regulation of RIT. To overcome these difficulties, it is essential to collect and disclose all information about the circumstances around this therapy in Japan. In this review, we would like to look at this therapy through several lenses, including historical, cultural, medical, and socio-economic points of view. We believe that clarifying the problems is sure to lead to the resolution of this complicated situation. We have also included several recommendations for future improvements. [ABSTRACT FROM AUTHOR]

Intraoperative gamma probe (GP) guidance with 99mTc-pertechnetate in the completion total thyroidectomy after a first thyroidectomy was investigated in this prospective study. The study group comprises of fourteen consecutive patients (14 females, age mean 50.2 ± 12.0 years, age range 29–73 years). All patients underwent a second thyroidectomy due to inadequate (5/14 patients) and complementary (9/14 patients) interventions. Serum-free three iodothyronine, free thyroxin and thyroid stimulating hormone measurements, a neck ultrasonography (USG) and thyroid scintigraphy (TS) were performed in the preoperative and postoperative period. After a 185 MBq (5 mCi) injection of 99mTc-pertechnetate, background (BG), left thyroid lobe (LTL), right thyroid lobe (RTL) and pyramidal tyroid lobe (PTL) regions were counted in time before and after resection of thyroid remnants by intraoperative GP. All resection materials were evaluated by histopathologic examination. Preoperative TSH was less than 30 mIU/mL (mean 21 ± 7) in all patients. Functioning thyroid remnants were shown in 13/14 patients on the preoperative TS and USG, which were diagnosed by USG in one but by TS in other one. We calculated that percentage median (minimum–maximum) values were 220.90% (56.00–411.11%) in LTL, 80.43% (11.54–471.05%) in RTL and 66.60% (−3.33 to 158.33%) in PTL for counts before resection, on the other hand, 15.96% (−20.55 to 47.62%) in LTL, 17.59% (−15.07 to 38.46%) in RTL and 17.59% (−1.96 to 57.14%) in PTL regions for counts after resection. There were statistically significant differences between these values belonging to before and after resection for LTL ( p = 0.001), RTL ( p = 0.001) and PTL ( p = 0.008). Bilateral small foci in a patient and unilateral focus in other patient were observed in postoperative TS. Unilateral focus was detected on the RTL by GP, but not bilateral foci. Postoperative TSH levels increased to 30 mIU/mL (mean 69 ± 26) at least. There was a statistically significant difference between preoperative and postoperative TSH values ( p < 0.001). Histopathologic confirmation revealed that all removed materials were the thyroid tissues. Gamma probe guidance with 99mTc-pertechnetate seemed to be a good option and easy available method in patients undergoing the completion total thyroidectomy. [ABSTRACT FROM AUTHOR]

18F-fluorodeoxyglucose positron emission tomography (FDG-PET) [or PET/computed tomography (CT)] is more likely to show false-negative results when it is performed shortly after chemotherapy and/or radiotherapy because of “metabolic stunning”. The present study aimed to evaluate the influence of I-131 therapy on FDG uptake and the detection of recurrence or metastasis of differentiated thyroid cancer (DTC). We retrospectively enrolled 16 consecutive FDG-PET/CT studies which had been performed in patients with DTC with elevated thyroglobulin (TG) but negative I-131 whole-body scan. All studies were performed under l-thyroxine suppression. The patients were divided into groups A and B for PET/CT performed within 4 months of I-131 therapy or no such therapy, respectively. Each lesion identified on PET/CT was characterized using a 5-point scale by visual analysis: 0 = definitely benign, 1 = probably benign, 2 = equivocal, 3 = probably malignant, and 4 = definitely malignant. The maximum standardized uptake value (SUVmax) in each lesion was also measured for semiquantitative analysis. We compared the visual grading and SUVmax of the lesion of highest FDG uptake between groups A and B. For visual analysis, group B had significantly more patients with an uptake score of 3 or 4 than group A (80% vs. 17%, P = 0.01). In addition, there were significantly more equivocal results from group A than from group B (67% vs. 10%, P = 0.02). If the patients with the highest uptake scores of 2, 3, and 4 were considered to be positive for local recurrence or metastasis, there would be no significant difference between the positive rates of groups A and B (83% vs. 90%, P = 0.7). However, the mean SUVmax of positive results was significantly lower for group A than for group B (3.1 ± 0.9 and 6.6 ± 3.5, respectively, P = 0.02). The preliminary results suggested that FDG uptake in DTC may be negatively influenced by I-131 therapy within 4 months, resulting in lower FDG uptake and more equivocal results. Further studies are necessary to determine whether it is secondary to “metabolic stunning” caused by I-131 therapy. [ABSTRACT FROM AUTHOR]

Unlabelled: Measurement of serum thyroglobulin (Tg) levels and I-131 whole body scintigraphy (WBS) are used in the follow-up of patients with differentiated thyroid cancer (DTC). This study was designed to evaluate the significance of persistent I-131 uptake in the thyroid bed in patients with DTC following surgery and/or radioactive iodine ablation. Tc-99m thyroid scintigraphy (TS) and I-131 thyroid uptake (IU) were also performed to determine their clinical impact on patient management.Patients and Methods: Sixty-two non-metastatic patients (14 men, 48 women) with a mean age of 44 years (range: 16-75) who had undergone surgical thyroidectomy for DTC were evaluated prospectively. All patients had undergone technetium and iodine scintigraphy (IS). Although serum Tg levels were measured in all patients, IU was available in 36.Results: Tg values were in the range of 0.2-24 ng/ml (median: 0.2 ng/ml) when patients were in the hypothyroid state. I-131 WBS detected residual tissue in the neck in 30 patients (48%); however TS was positive in only 12 (19%). I-131 uptake in the thyroid bed ranged from 0 to 14% (median: 0.1%). Twelve of 13 patients with positive IS and negative TS had uptake values < or = 0.3% (p < 0.00001). When IU values were < or = 0.3%, 54% of our patients did not have any uptake in the thyroid bed on TS or IS, whereas when IU was > 0.3%, 80% of patients had neck uptake on both TS and IS (p < 0.00001).Conclusion: The results of this study demonstrate that the concordance of IS and TS depends on the IU level after suspension of replacement therapy. Measurements of IU and TS are of considerable value in evaluating patient response to therapy and will substantially reduce the need for repetitive radioiodine scans and unnecessary treatment doses in patients with undetectable Tg values. [ABSTRACT FROM AUTHOR]

Coincidence imaging with a dual-head gamma camera may offer a cost-effective alternative to dedicated PET. The aim of this study was to compare the diagnostic accuracy of coincidence imaging and PET in patients with differentiated thyroid cancer. Thirty-one patients were studied after thyroidectomy and radioiodine ablation. They were injected with a single dose of 300 MBq 18F-FDG. Scanning was performed on a dedicated PET system after 1 hr, and on a coincidence gamma camera after 4 hrs. Based on a lesion-by-lesion comparison, coincidence imaging and PET concurred in 69% of 118 lesions. Based on lesion size, concurrence was 96% in lesions larger than 1.5 cm, and 62% in those between 1 and 1.5 cm. Lesions smaller than 1 cm could not be identified with coincidence imaging. Identical staging was obtained with coincidence imaging and PET in 26/31 patients (84%). In four patients FDG accumulating lesions were shown by both the coincidence camera and the dedicated scanner, but not detectable with any other imaging means and were confirmed histologically on surgery. Although a coincidence camera is technically inferior to a dedicated PET scanner, it may provide clinically useful results in situations were a lesion of sufficient size and FDG uptake is to be expected, e.g. when evaluating a known lesion for malignancy. [ABSTRACT FROM AUTHOR]