FDG-PET performed concurrently with initial I-131 ablation for differentiated thyroid cancer

Objective  

Differentiated thyroid cancers (DTCs) are commonly treated by total thyroidectomy followed by I-131 radioiodine ablation to eradicate any residual thyroid tissue and to detect any metastatic lesions on post-treatment whole body scans (TxWBS). However, some DTCs do not trap iodine, resulting in negative whole body scanning. Fluorine-18-fluorodeoxyglucose positron emission tomography (FDG-PET) has proven to be a valuable diagnostic technique for detecting many types of malignant tumors and metastases. The purpose of this study was to evaluate FDG-PET performed concurrently with initial I-131 ablation for its ability to detect lymph node metastasis and for its role in the management of DTC patients.     

Application of a medium-energy collimator for I-131 imaging after ablation treatment of differentiated thyroid cancer

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.     

The outcome of I-131 ablation therapy for intermediate and high-risk differentiated thyroid cancer using a strict definition of successful ablation

Purpose

This article examines the outcome of radioactive iodine ablation therapy for thyroid cancer in high-risk patients and investigates background factors influencing ablation failure.

Materials and methods

We included 91 patients in this retrospective analysis and evaluated the ablation success rate. Successful ablation was defined as the absence of visible iodine-131 (I-131) accumulation in the thyroid bed after whole-body scans and thyroglobulin levels <2 ng/ml in a TSH-stimulated state after ablation. We extracted data on patients’ age, sex, I-131 dose, pathology, resection stump findings, tumor T category and thyroglobulin levels, which could affect ablation outcome.

Results

Successful ablation was achieved in only 14 patients (15.4%). Pre-ablation serum thyroglobulin levels were significantly higher in the ablation failure group than in the success group (P < 0.001), while no significant differences were found for other factors between the groups. Furthermore, thyroglobulin levels >10 ng/ml were significantly related to ablation failure after multivariate analysis (odds ratio 27.2; 95% confidence interval 2.469–299.7; P = 0.007).

Conclusion

The ablation success rate was very low because of high thyroglobulin levels, even with high-dose I-131. High-risk patients, especially those with high thyroglobulin levels (>10 ng/ml), are unlikely to reach levels low enough to meet successful ablation criteria.

     

Predictive factors for the outcomes of initial I-131 low-dose ablation therapy to Japanese patients with differentiated thyroid cancer

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.

     

The influence of I-131 therapy on FDG uptake in differentiated thyroid cancer

OBJECTIVE: 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). METHODS: 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 (SUV max) in each lesion was also measured for semiquantitative analysis. We compared the visual grading and SUV max of the lesion of highest FDG uptake between groups A and B. RESULTS: 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 SUV max 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). CONCLUSIONS: 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.     

Radiation dose to the testes after 131I therapy for ablation of postsurgical thyroid remnants in patients with differentiated thyroid cancer.

Radioiodine-131 is used in differentiated thyroid cancer (DTC) for ablation of postsurgical thyroid remnants and destruction of metastases. The question may be raised of whether 131I treatment of DTC in male patients may give an irradiation dose to the testes that could impair fertility. Few data in the literature concern the dose absorbed by the testes after 1311 therapy for DTC. Because 131I kinetics may be altered by the hypothyroid condition commonly present at the time of treatment and by the radioiodinated iodoproteins released by the damaged thyroid tissue, the dose values reported in the International Commission on Radiological Protection (ICRP) tables for euthyroid men may not be appropriate. To clarify this problem, three male subjects undergoing 131I therapy for ablation of thyroid remnants shortly after thyroidectomy for DTC were studied. METHODS: The mean administered activity was 1256 MBq, and the duration of the study was 2 wk. The gamma dose was measured by thermoluminescent dosimeters (TLDs) applied to the lower poles of the testes. Correction factors were calculated for the distance of the TLD from the center of the testes and for attenuation by the testes of the gamma rays reaching the TLD. After correction, the gamma dose to the testes ranged from 21 to 29 mGy. The gamma dose calculated by the Medical Internal Radiation Dose (MIRD) method from blood and urine samples was similar (18-20 mGy) to that measured by TLDs. The beta dose was estimated by the MIRD method from blood activity and testicular volume and ranged between 14 and 31 mGy. Results: The total (beta and gamma) doses to testes were 30, 33 and 43 microGy/MBq in the three subjects. CONCLUSION: These values are close to those derived from the ICRP tables (26-37 microGy/MBq 131I) for euthyroid subjects. The present data indicate that significant irradiation is delivered to the testes after the administration of the 131I ablative dose to thyroidectomized patients. The relevance of the radiation absorbed by testes on fertility remains to be established.     

Comparisons of I-123 diagnostic and I-131 post-treatment scans for detecting residual thyroid tissue and metastases of differentiated thyroid cancer

Objective  

We assessed the performance of 37 MBq I-123 as a diagnostic imaging agent in patients with differentiated thyroid cancer using comparisons with their corresponding high-dose post-treatment I-131 scans.     

Lung uptake on I-131 therapy and short-term outcome in patients with lung metastasis from differentiated thyroid cancer

Objective

It is sometimes difficult to assess I-131 lung uptake at the initial I-131 therapy because of strong artifacts from I-131 uptake in the thyroid bed. The aim of this study was to analyze the lung uptake at the second I-131 therapy for lung metastasis in patients who did not have lung uptake at the initial therapy from differentiated thyroid carcinoma (DTC). Then, we also analyzed the relationship between the initial lung uptake and short-term outcome after I-131 therapies.

Methods

This study included 62 DTC patients with lung metastasis. The patients were classified into 2 groups according to the lung uptake at the initial I-131 therapy such as patients with lung uptake (positive uptake group n = 31) and those without lung uptake (negative uptake group n = 31). The lung uptake was analyzed at the second therapy in both groups. The short-term outcome was also analyzed based on the CT findings of lung metastasis size and serum thyroglobulin level between the two groups.

Results

The positive uptake group showed positive lung uptake at the second therapy in 23 patients (74 %), whereas none of negative uptake group showed any lung uptake at the second therapy (P < 0.01). The positive uptake group significantly decreased in the size of lung metastasis from the initial therapy to the second therapy (20.0 ± 11.7 to 16.6 ± 9.6 mm, P < 0.01) with further decrease after the second therapy (P < 0.05). The serum thyroglobulin level was also significantly decreased from the initial therapy to the second therapy (4348 ± 7011 to 2931 ± 4484 ng/ml, P < 0.05). In contrast, the negative uptake group significantly increased in the size of lung metastasis from the initial therapy to the second therapy (17.3 ± 12.2 to 19.9 ± 14.3 mm, P < 0.01) with further increase after the second therapy (P < 0.01).

Conclusion

No patients without lung uptake at the initial I-131 therapy showed lung uptake at the second therapy, or showed treatment effect. Therefore, second I-131 therapy for these patients with initially negative lung uptake should be considered cautiously.     

Maximal safe dose of I-131 after failure of standard fixed dose therapy in patients with differentiated thyroid carcinoma

Objective  The maximal safe dose (MSD) on the basis of bone marrow irradiation levels allows the delivery of a large amount of I-131 to thyroid cancer tissue. The efficacy of MSD therapy in differentiated metastatic thyroid cancers that persisted after conventional fixed dose therapy is investigated. Methods  Forty-seven differentiated thyroid carcinoma patients with non-responsive residual disease despite repetitive fixed dose I-131 therapy were enrolled in this study. Their postoperative pathologies were 43 papillary carcinomas and 4 follicular carcinomas. The MSD was calculated with the Memorial Sloan-Kettering Cancer Center protocol using serial blood samples. The MSDs were administered at intervals of 6 months. Treatment responses were evaluated using I-131 whole-body scans and serum thyroglobulin measurements. Results  The mean calculated MSD was 12.5 ± 2.1 GBq (339.6 ± 57.5 mCi). Of the 46 patients, 7 (14.9%) showed complete remission, 15 (31.9%) partial remission, 19 (40.4%) stable disease, and 6 (12.8%) disease progression. Of the patients who showed complete or partial remission, 15 (65%) showed response after the first MSD session and 6 (26%) showed response after the second session. Twenty-nine patients (62%) experienced transient cytopenia after therapy, but three did not recover to the baseline level. Conclusions  The maximal safe dose provides an effective means of treatment in patients who failed to respond adequately to conventional fixed dose therapy. I-131 MSD therapy can be considered in patients who fail fixed dose therapy.     

分化型甲状腺癌患者^131I治疗后体内残留放射性活度的评估

目的 评估分化型甲状腺癌（DTC）患者^131I治疗后体内残留放射性活度.方法 本研究共纳入了35例DTC患者,分为“清甲”（20例）与“清灶”（15例）组,分别于服^13I后2、6、24、48、72 h进行^131I全身显像及1m处当量剂量率的测定,以2h时显像计数和活度作为总计数和总活度.根据各时间点显像计数与2h的显像计数比值间接估算体内残留放射性活度,并估算患者体内残留放射性活度达到400 MBq时的1m处当量剂量率.统计学分析采用直线相关与回归分析.结果 “清甲”组服^131I后2、6、24、48、72 h体内残留^131I活度占服^131I总活度的百分比分别为99％±4％、86％±6％、35％±10％、12％±8％、7％±8％, “清灶”组分别为99％±1％、91％±7％、47％±17％、11％±9％、4％±6％. “清甲”组服^131I后2、6、24、48、72 h的1m处当量剂量率分别为（157±37）、（120±36）、（35±13）、（11±9）、（9±11）μSv/h,“清灶”组分别为（234±43）、（186±51）、（49±20）、（12±11）、（4±6）μSv/h.体内残留的放射性活度与1m处当量剂量率呈正相关（r=0.87,P＜0.001）.“清甲”与“清灶”组服^131I后48、72 h体内残留放射性活度分别为（432±292）、（265±281） MBq及（731±701）、（277±470） MBq,对应的1m处当量剂量率为8～ 11 μSv/h.结论 DTC患者服^131I后48～72 h体内残留放射性活度达到国家标准规定的400 MBq时,即DTC患者1m处当量剂量率达到8～11 μSv/h时方可出院.     

No survival difference after successful 131I ablation between patients with initially low-risk and high-risk differentiated thyroid cancer

Purpose

To compare disease-specific survival and recurrence-free survival (RFS) after successful ¹³¹I ablation in patients with differentiated thyroid carcinoma (DTC) between those defined before ablation as low-risk and those defined as high-risk according to the European Thyroid Association 2006 consensus statement.

Methods

Retrospective data from three university hospitals were pooled. Of 2009 consecutive patients receiving ablation, 509 were identified as successfully ablated based on both undetectable stimulated serum thyroglobulin in the absence of antithyroglobulin antibodies and a negative diagnostic whole-body scan in a follow-up examination conducted 8.1±4.6 months after ablation. Of these 509 patients, 169 were defined as high-risk.

Results

After a mean follow-up of 81±64 months (range 4–306 months), only three patients had died of DTC, rendering assessment of disease-specific survival differences impossible. Of the 509 patients, 12 (2.4%) developed a recurrence a mean 35 months (range 12–59 months) after ablation. RFS for the duration of follow-up was 96.6% according to the Kaplan-Meier method. RFS did not differ between high-risk and low-risk patients (p=0.68). RFS differed slightly but significantly between those with papillary and those with follicular thyroid carcinoma (p=0.03) and between those aged ≤45 years those aged >45 years at diagnosis (p=0.018).

Conclusion

After (near) total thyroidectomy and successful ¹³¹I ablation, RFS does not differ between patients classified as high-risk and those classified as low-risk based on TNM stage at diagnosis. Consequently, the follow-up protocol should be determined on the basis of the result of initial treatment rather than on the initial tumour classification.     

甲状腺癌术后131I治疗

甲状腺癌确诊后，经典的治疗方法是近全切除术后加131I治疗。研究表明，NIS(钠／碘同向转运体)具有聚碘能力，而TPO(甲状腺过氧化物酶)能抑制碘从细胞中流出，NIS和TPC基因联合转染肿瘤细胞介导~(131)I治疗有可能成为一种新的治疗方法；维加酸可诱导失分化肿瘤细胞的摄碘能力恢复或提高，也有利于~(131)I治疗。     

Sialadenitis following I-131 therapy for thyroid carcinoma: concise communication

During a 4-yr period, ten of 87 patients (11.5%) who received therapeutic doses of radioactive iodine (I-131) for thyroid carcinoma developed acute and/or chronic sialadenitis involving the parotid (five patients) or submandibular (four patients) glands, or both (one patient). Nine of the 10 patients had received prior I-131 therapy; the precipitating I-131 dose varied between 10 and 164 mCi. Onset of symptoms occurred between 1 day and 6 mo following therapy and the duration varied from 3 wk to 21/2 yr. This complication occurs more often than has been appreciated.     

用 131I治疗不能切除的分化型甲状腺癌转移性淋巴结

目的　探讨1 31 I治疗不能手术切除的分化型甲状腺癌转移性淋巴结 (LMDTC)的治疗剂量和疗效。方法　对 2 4例分化型甲状腺癌术后不能手术切除的 84个LMDTC ,在 7 4～ 16 6 5GBq范围内选择不同剂量1 31 I治疗。分别于治疗后 1、3、6和 12个月随访观察LMDTC的状况。对≥ 2cm的LMDTC ,1 31 I治疗后视其变化确定再手术切除时间。结果　 84个不能手术切除的分化型LMDTC ,1 31 I治疗后有 78个分别消除、缩小和再次手术切除 ,有效率为 92 9% (78 84个 )。对 37个≥ 2cm的LMDTC1 31 I治疗后结合再手术治疗 ,切除病灶 16个 ,再切除率占 4 3 2 % (16 37个 )。与单纯用1 31 I治疗 <2cm的LMDTC的结果比较 ,差异有极显著性 (P <0 0 1)。1 31 I剂量为 3 7～ 12 95GBq时 ,各剂量组对LMDTC的疗效差异无显著性 (P均 >0 0 5 )。结论　大剂量1 31 I治疗分化型LMDTC有较好的疗效。     

分化型甲状腺癌131I治疗的争议与探索

分化型甲状腺癌（DTC）患者在规范的手术、选择性131I治疗、TSH抑制治疗下多数预后良好。131I治疗目标分为清甲治疗、辅助治疗及清灶治疗,其可完善疾病分期、便于随诊、降低疾病复发及死亡风险,但临床实践中仍在存诸多待明确的问题,如术后131I治疗前评估中,亚临床病灶判断困难,且无用以指导治疗的Tg临界值,增加了辅助治疗的决策难度;治疗后随诊中,尚无评价结构性病灶131I治疗疗效的标准;TgAb的存在会影响病情判断;131I累积剂量相关并发症亦需监测管理。本期重点号刊登了数篇DTC患者131I治疗相关的文章,多方位讨论了当下131I治疗中的难点和我国学者的探索。