Reproducibility of whole-body <Superscript>131</Superscript>I scan and serum thyrotropin and stimulated thyroglobulin values in patients studied twice after injection of recombinant human thyrotropin

Purpose Recombinant human TSH (rhTSH) is used to increase radioiodine uptake during imaging of thyroid cancer, obviating the need to render the patient hypothyroid. We assessed the reproducibility of radioiodine uptake, serum thyrotropin (TSH), and stimulated serum thyroglobulin (Tg) levels after rhTSH administration. Methods A retrospective review was performed of patients at Stanford who underwent whole-body ¹³¹I scanning for surveillance of thyroid cancer twice after thyroidectomy and ¹³¹I ablation, with rhTSH prior to each scan. Forty-eight hour radioiodine uptake, peak serum TSH, and stimulated serum Tg levels for each study were recorded. Paired t tests and correlation analysis were used to assess interexamination repeatability. Results Twenty-three patients underwent two scintiscans with rhTSH, for a total of 46 exams. There was no significant difference between percent uptake at 48 h in the paired exams (p=0.40). Serum TSH level was measured in 45 of 46 exams; TSH exceeded 50 mIU/l in all cases, and there was no significant difference between paired TSH levels (p=0.93). All patients had stimulated serum Tg levels measured, with no significant difference between paired Tg levels (p=0.40); after excluding one patient whose Tg changed from 15.8 ng/ml to undetectable between scans without interval treatment, the p value rose to 0.95. There was a strong correlation among paired uptake values (r=0.85, p<0.0001), peak serum TSH (r=0.69, p=0.0003), and stimulated Tg levels (r=0.81, p<0.0001). No discordant scan interpretations were reported. Conclusion Forty-eight hour radioiodine uptake, peak serum TSH, and stimulated serum Tg levels after administration of rhTSH are repeatable between studies, demonstrating reproducibility of diagnostic results without rendering patients hypothyroid.     

Radioiodine-131 in differentiated thyroid cancer: a retrospective analysis of an uptake-related ablation strategy

In our hospital, a 24-h radioiodine-131 (¹³¹I) uptake-related ablation strategy is used in patients with differentiated thyroid cancer to destroy thyroid remnants after primary surgery. In this strategy, low doses of ¹³¹I are used, but data in the literature on its efficacy are conflicting. Therefore, we performed the present study to evaluate the clinical outcome of this ablation strategy. In this study, patients (n=235) were selected who underwent thyroidectomy for differentiated thyroid cancer, followed by an ablative dose of ¹³¹I. Approximately 6 months after ablation, treatment efficacy was evaluated using radioiodine scintigraphy and thyroglobulin (Tg) measurements. Successful ablation was defined as the absence of radioiodine uptake in the neck region (criterion 1). Tg values were determined 3–12 months after ablation (criterion 2). Based on criterion 1, unsuccessful ablation was found in 43.0% of cases. Pre-treatment uptake values were statistically significantly lower (P=0.003) in successfully ablated patients (mean 5.4%) than in unsuccessfully ablated patients (mean 8.2%). Based on criterion 2, unsuccessful ablation was found in 52.4% of patients. The uptake-related ablation strategy, using low doses of ¹³¹I, shows a relatively high treatment failure rate. Based on these results it is suggested that a lower ablation failure rate could be achieved by applying higher ¹³¹I doses in the ablation of thyroid remnants in differentiated thyroid carcinoma patients. In the case of lymph node metastases a further dose adjustment may be advisable.     

Possible explanations for patients with discordant findings of serum thyroglobulin and 131I whole-body scanning.

The long-term monitoring of patients with differentiated thyroid carcinoma (DTC) is essential throughout the patient's life after total or near-total thyroidectomy followed by (131)I remnant ablation and thyroid hormone suppression of thyroid-stimulating hormone (TSH). Sensitive surveillance for DTC recurrence and metastases includes radioiodine diagnostic whole-body scanning (DWBS) and measurement of serum thyroglobulin (Tg) after endogenous or exogenous TSH stimulation. Serum Tg levels during thyroid hormone withdrawal (Tg-off) are usually well correlated with the results of DWBS. In general, undetectable Tg levels with negative DWBS (DWBS(-)) suggest complete remission, whereas detectable or elevated Tg concentrations are suggestive of the presence of (131)I uptake in local or distant metastases. However, DTC patients with discordant results of Tg measurement and (131)I WBS have been observed in the follow-up study. Negative (131)I DWBS and a positive Tg test (DWBS(-) Tg(+)) are found in most of these cases. Positive (131)I DWBS and a negative Tg test (DWBS(+) Tg(-)), though of uncommon occurrence, has also been demonstrated in a small but significant number of cases. With this scenario, one should first attempt to uncover a cause for possibly false-negative or false-positive (131)I WBS or serum Tg. Explanations for the discordance are speculative but should be scrutinized when confronted with discrepant data in a given patient.     

Is empiric 131I therapy justified for patients with positive thyroglobulin and negative 131I whole-body scanning results?

The long-term monitoring of patients with differentiated thyroid carcinoma (DTC) is essential throughout the patient's life after total or nearly total thyroidectomy followed by 131I remnant ablation and thyroid hormone suppression of thyroid-stimulating hormone (TSH). Sensitive surveillance for DTC recurrences and metastases includes radioiodine diagnostic whole-body scanning (DWBS) and measurement of serum thyroglobulin (Tg) levels after endogenous or exogenous TSH stimulation. Serum Tg levels during thyroid hormone withdrawal usually are correlated well with the results of DWBS. In general, Tg levels undetectable by DWBS suggest complete remission, whereas detectable or elevated Tg concentrations are suggestive of the presence of 131I uptake in local or distant metastases. However, DTC patients with a positive Tg test and negative 131I DWBS results (Tg+ DWBS-) have been observed in follow-up studies. The management of these cases begets controversy. METHODS: We electronically searched Medline (1966-2004.3), Embase (1984-2003), the Cochrane Library (2004, 2nd edition), CNKI (1994-2004), and CBM-DISC (1978-2004). We also manually searched the Chinese Journal of Isotopes, Radiologia pratica, and the Chinese Journal of Endocrinology and Metabolism. RESULTS: Ten serial observations and 3 nonrandomized controlled trials were found. The available data showed that of 314 patients who were treated empirically with 131I, 194 (62%) of 314 displayed pathologic uptake in the thyroid bed, lung, bone, mediastinum, and lymph nodes. In studies with Tg-on and Tg-off data, 171 (63%) of 271 patients achieved a decrease in Tg. CONCLUSION: On the basis of data from recent studies, 131I therapy should be individualized according to clinical characteristics. More significantly, a decrease in Tg levels was achieved in 63% of DTC patients with Tg+ DWBS-, suggesting that 131I therapy does have a therapeutic effect when the Tg level is considered an index of tumor burden. The 62% positive posttherapy whole-body scanning results also indicated that a therapeutic dose of 131I could reveal approximately one half of previously undiagnosed lesions in some patients. Therefore, 131I therapy may be justified in patients with Tg levels of > 10 microg/L and DWBS- and who are at high risk of any recurrence.     

Differentiated thyroid cancer: radioiodine following lobectomy - a clinical feasibility study

The surgical management of differentiated thyroid cancer remains controversial. Total thyroidectomy has been associated with higher rates of post-operative morbidity than more conservative surgery, but radioiodine ablation of residual thyroid tissue is considered to be particularly difficult after lobectomy. The purpose of this retrospective study was to assess the feasibility of 131I ablation after lobectomy, compared with total thyroidectomy, in patients who had undergone surgery for differentiated thyroid carcinoma. A retrospective analysis was performed of 225 post-surgical thyroid cancer patients treated with 3500 MBq 131I for the ablation of thyroid remnants. One hundred and sixty-five patients (73%) had previously undergone total thyroidectomy, whilst 60 patients (27%) had been treated by lobectomy. All patients underwent diagnostic scintigraphy, with 40 MBq 131I, 2 days prior to ablative therapy and at 3 months post-ablation. The median pre-ablative 131I neck uptake values were 3.3% and 20.1% in patients treated by total thyroidectomy and lobectomy, respectively (P < 0.001). Pre-ablation neck uptake correlated strongly with the whole-body 131I burden 2 days after 131I therapy (P < 0.001), and the biological half-life of the radioiodine was markedly longer after lobectomy than after total thyroidectomy. Ninety-eight per cent of patients treated by total thyroidectomy were successfully ablated by one 131I treatment, compared with 90% after lobectomy (P < 0.05). There were no significant differences in 131I neck uptake or serum thyroglobulin levels between the two patient groups at 3 months post-ablation. These data show that high rates of thyroid ablation can be achieved with a single fixed dose of 131I after thyroid lobectomy. The use of this surgical procedure may result in a longer period of patient isolation than that required after total thyroidectomy. However, the clear correlation between pre-ablation neck uptake and 131I burden at 2 days post-therapy enables effective treatment scheduling, so making lobectomy followed by 131I ablation a practical option for the management of differentiated thyroid cancer.     

Radioiodine lobar ablation as an alternative to completion thyroidectomy in patients with differentiated thyroid cancer

This study seeks to evaluate the role of radioiodine in the ablation of the remaining thyroid lobe, following a histopathological diagnosis of minimally invasive follicular carcinoma or papillary carcinoma of > or =1.5 cm size in patients undergoing hemithyroidectomy. There were 93 patients (69 females and 24 males) with an average age of 37.3+/-12.5 years (range, 16-70 years) and a mean follow-up duration of 46 months. Sixty-six of the patients had papillary cancer and remaining 27 had follicular thyroid cancer. The mean 24 h radioiodine neck uptake at the first visit was 17.2+/-7.3% (4.4-34%). In view of the large amount of thyroid tissue to be ablated, which may produce radiation induced thyroiditis, low doses of radioiodine (15-60 mCi) were administered to the patients. The patients were evaluated 6 months after radioiodine therapy with a 131I whole-body scan and 48 h radioiodine neck uptake, and a thyroglobulin assay after 4-6 weeks of levothyroxine withdrawal. The thyroid lobe was completely ablated in 53 patients (56.9%) after one dose of I and the remaining patients had partial thyroid ablation, with the mean radioiodine neck uptake being reduced to 3.1+/-2.4%. The mean first dose of 131I was 31.8+/-11.7 mCi; the estimated mean absorbed dose was 251.3+/-149.3 Gy (range, 120-790 Gy). Around 30% patients, in each of whom a remnant thyroid lobe was ablated with a single dose of radioiodine, received < or =200 Gy. The cumulative ablation rate was 92.1% after two doses of 131I. Only seven patients needed a third dose of 131I. In our cohort, 15 patients (16.1%) complained of throat discomfort and neck pain. All of them were managed with mild analgesics except three patients who needed additional oral prednisolone for 7-10 days to overcome neck oedema. We conclude that, although completion thyroidectomy remains the standard treatment after hemithyroidectomy in cases of differentiated thyroid cancer, radioiodine ablation of an intact thyroid lobe is possible and it can be achieved with much smaller doses of radioiodine than previously believed. Lobar ablation is an attractive alternative to surgery for those who refuse to undergo completion thyroidectomy or had complications during initial surgery. However, the long-term outcome in this subset of patients remains to be determined.     

Detection and treatment of lung metastases of differentiated thyroid carcinoma in patients with normal chest X-rays

Lung metastases were demonstrated by total-body 131I scans in 23 patients with differentiated thyroid carcinoma, at a time when chest x-ray was normal. This total-body 131I scan was performed after the administration of 2 mCi (in 11 patients) or 100 mCi (in 12 patients). Overall uptake of 131I in lungs was less than 1% of the administered dose in 11 patients. All patients were treated with radioiodine. No lung uptake was found in 20 patients at the last 100 mCi post-therapy scan. Among them, Tg level became undetectable during T4 treatment in eight, lung CT scan showed the disappearance of the micronodules in seven, and lung biopsy did not show evidence of disease in two patients. No patient developed radiation lung fibrosis. In conclusion, favorable responses to radioiodine treatment were observed despite relatively low overall uptake, in relation to the small size of lung metastases. This provides high concentrations of radioiodine and therefore high radiation doses.     

Value of the first serum thyroglobulin level after total thyroidectomy for the diagnosis of metastases from differentiated thyroid carcinoma.

The aim of this study was to evaluate the diagnostic significance of the first serum thyroglobulin (Tg) measurement, performed 40 days after total thyroidectomy for differentiated thyroid carcinoma and prior to the ablation of residual thyroid tissue by means of iodine-131 therapy. In a retrospective study we examined 334 consecutive patients followed up for 4-16 years by means of regular Tg measurements, (131)I whole-body scans (WBS) and other diagnostic techniques, if necessary. In 79 patients metastases were discovered (32 lymph node and 47 distant metastases) within 18 months following thyroidectomy. Mean values of first Tg were significantly higher in patients with than in patients without metastases (258.9+/-310.6 vs 15.9+/-19.6 ng/ml; P<0.0001). Receiver operating characteristic (ROC) curve analysis of data revealed that for first Tg values higher than 69.7 ng/ml, the positive predictive value for the presence of metastases exceeded 90%. No statistically significant correlation was found between first Tg value and either thyroid-stimulating hormone (TSH) value or percentage of (131)I uptake by residual thyroid tissue. No other parameter (age, histological type, site of metastases, (131)I uptake by metastases) was significantly related to the first Tg value. We conclude that the first Tg measurement after total thyroidectomy provides a useful early diagnostic indication of metastatic disease in spite of the presence of a post-surgical thyroid remnant, and that this holds true regardless of the TSH value and WBS result. This early information is of clinical relevance for patient follow-up.     

Value of technetium scintigraphy and iodine uptake measurement during follow-up of differentiated thyroid cancer

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.     

Fixed dosage of 131I for remnant ablation in patients with differentiated thyroid carcinoma without pre-ablative diagnostic 131I scintigraphy

Differentiated thyroid cancer is treated by (near) total thyroidectomy followed by radioiodine (131I) ablation of the residual active tissue in the thyroid bed. Controversy remains concerning the use and the dose of pre-ablative diagnostic 131I scintigraphy. This study was designed to assess the efficacy of thyroid ablation by high-dose 131I without pre-ablative diagnostic 131I scintigraphy. Ninety-three patients were treated with (near) total thyroidectomy and with a high ablative dose of 131I (3700-7400 MBq). A preablative 131I diagnostic scintigram was not performed. To assess the efficacy of the treatment, all patients were studied with a diagnostic 131I scintigram and with thyroglobulin plasma assays 1 year later after withdrawal of L-thyroxine for 4-6 weeks. The main criterion for a successful ablation was the absence of thyroid bed activity. An additional criterion was a thyroglobulin value of <10 microg x l(-1). Successful ablation according to the main criterion was obtained in 88% of patients. Forty patients (43%) showed no neck uptake and had undetectable serum thyroglobulin. Twenty-two patients (25%) had serum thyroglobulin concentrations between 1 and 10 microg x l(-1). Twenty-six patients (27%) had thyroglobulin >10 microg x l(-1), 19 patients showing residual thyroid uptake or metastatic lesions. We conclude that high-dose radioiodine ablation without prior diagnostic scintigraphy results in a high rate of successful ablation, preventing repeat 131I treatment.     

Value of the first serum thyroglobulin level after total thyroidectomy for the diagnosis of metastases from differentiated thyroid carcinoma

The aim of this study was to evaluate the diagnostic significance of the first serum thyroglobulin (Tg) measurement, performed 40 days after total thyroidectomy for differentiated thyroid carcinoma and prior to the ablation of residual thyroid tissue by means of iodine-131 therapy. In a retrospective study we examined 334 consecutive patients followed up for 4–16 years by means of regular Tg measurements, ¹³¹I whole-body scans (WBS) and other diagnostic techniques, if necessary. In 79 patients metastases were discovered (32 lymph node and 47 distant metastases) within 18 months following thyroidectomy. Mean values of first Tg were significantly higher in patients with than in patients without metastases (258.9±310.6 vs 15.9±19.6 ng/ml; P<0.0001). Receiver operating characteristic (ROC) curve analysis of data revealed that for first Tg values higher than 69.7 ng/ml, the positive predictive value for the presence of metastases exceeded 90%. No statistically significant correlation was found between first Tg value and either thyroid-stimulating hormone (TSH) value or percentage of ¹³¹I uptake by residual thyroid tissue. No other parameter (age, histological type, site of metastases, ¹³¹I uptake by metastases) was significantly related to the first Tg value. We conclude that the first Tg measurement after total thyroidectomy provides a useful early diagnostic indication of metastatic disease in spite of the presence of a post-surgical thyroid remnant, and that this holds true regardless of the TSH value and WBS result. This early information is of clinical relevance for patient follow-up. Received 26 October 1998 and in revised form 12 June 1999     

不同剂量首次131I去除甲状腺术后残留组织疗效比较

目的 回顾分析343例DTC病例,比较不同剂量首次131I去除甲状腺术后残留组织(RRA)疗效,并分析影响疗效的因素.方法 343例DTC患者行甲状腺全切术或近全切术,术后经影像学检查无局部或远处转移.以首次131I剂量将343例患者分为3组:A组101例,剂量为1850 ～2220 MBq;B组103例,剂量为2590～2960 MBq;C组139例,剂量为3330～3700 MBq.RRA后随访6～12个月.判断RRA成功标准:(1)131I全身扫描甲状腺床未见放射性摄取;(2) TSH刺激状态的Tg＜10 μg/L.应用SPSS 15.0软件对数据进行x2检验和logistic回归分析.结果 (1)343例患者RRA成功率63％( 215/343);(2)A、B和C组成功率分别为59％( 60/101)、64％( 66/103)和64％(89/139),3组疗效差异无统计学意义(x2=0.657,P=0.720);(3)单因素分析:筛选出性别(P=0.030)、手术方式(P＜0.01)、手术次数(P=0.004)、治疗前TSH(P =0.019)、治疗前Tg水平(P＜0.01)为有关因素,剔除年龄(P=0.420)、病理类型(P =0.585)、淋巴结转移(P =0.858)、多灶(P=0.365)、TNM分期(P =0.388)和剂量(P=0.733)等无关因素,将有关因素进行logistic回归分析,手术方式(P＜0.01)和治疗前Tg水平(P＜0.O1)是影响RRA疗效的因素.结论 DTC患者甲状腺全切或近全切术后,小剂量1850 ～ 2220 MBq RRA与大剂量3330～ 3700 MBq RRA疗效相同.术式和治疗前Tg水平是影响RRA成功的重要因素.     

甲状腺癌术后131I首次清除剩余甲状腺疗效分析

目的　观察不同年龄、性别、病理类型、手术方式、术后13 1I治疗时间、13 1I剂量、TSH水平以及剩余甲状腺外转移灶是否同时摄碘等因素对分化型甲状腺癌术后患者首次13 1I清除剩余甲状腺的影响。方法　分化型甲状腺癌术后患者 85例 ,手术治疗后 ,口服13 1I 1.11～ 5 .5 5GBq进行首次13 1I治疗 ,3～ 6个月后随访 ,以颈部剩余甲状腺显像与周围本底相比未见摄碘为成功清除的标准。结果85例中成功者 5 8例 ,成功率 6 8.2 %。不同的13 1I剂量、手术方式、术后首次治疗时间、TSH水平的变化以及剩余甲状腺外转移灶是否同时摄碘分别与成功率有一定关系 ;其中术后首次治疗时间与成功率之间呈负相关 (r=- 1.10 84,r0 .0 1( 3 ) =0 .95 9,P <0 .0 1)。不同年龄、性别及病理类型与成功率之间无明显关系。结论　适当的13 1I剂量、甲状腺全切手术、术后首次13 1I治疗时间 3个月以内、5 0mU/L以上的TSH水平以及仅有剩余甲状腺摄碘的分化型甲状腺癌术后患者疗效较好。疗效与患者的年龄、性别及病理类型无关     

Procedure guideline for iodine-131 whole-body scintigraphy for differentiated thyroid cancer (version 3)

Version 3 of the procedure guideline for (131)I whole-body scintigraphy (WBS) is the counterpart to the procedure guideline for radioiodine therapy (version 3) and specify the interdisciplinary guideline for thyroid cancer of the Deutsche Krebsgesellschaft concerning the nuclear medicine part. (131)I WBS 3-6 months after (131)I ablation remains a standard procedure in an endemic area for thyroid nodules and the high frequency of subtotal surgical procedures. Follow-up without (131)I WBS is only justified if the following preconditions are fulfilled: low-risk group pT1-2, pN0 M0 with histopathologically confirmed pN0, (131)I uptake <2%, (131)I WBS during ablation without any suspicious lesion, stimulated thyroglobulin (Tg)-level 3-6 months after ablation <2 ng/mL, and absence of anti-thyroglobulin-antibodies with normal recovery-testing. If patients from the low-risk group show normal (131)I WBS 3-6 months after ablation and stimulated Tg is of <2 ng/mL, there will be no need for additional routine (131)I WBS. If patients from the high-risk group show normal (131)I WBS and stimulated Tg-level of <2 ng/mL 3-6 months after ablation, the follow-up care should include repeated stimulated Tg-measurements. If the Tg-level remains below 2 ng/mL, an additional (131)I WBS will be not necessary. The recommended intervals for stimulated Tg-testing are adapted to the prior intervals for (131)I WBS-testing in the high-risk group. Increased anti-thyroglobulin-antibodies or incomplete recovery-testing make an individual strategy of follow-up care necessary, which include (131)I WBS.     

Self-stunning in thyroid ablation: evidence from comparative studies of diagnostic 131I and 123I

Twenty-six patients who had undergone recent surgery for differentiated thyroid cancer were investigated using iodine-131 iodide (120 MBq). Uptake in the thyroid bed was measured at 3 days using a dual-head gamma camera. An ablation activity of 131I iodide (4,000 MBq) was administered 3-38 (median 14) days later and uptake in the thyroid bed measured once or twice, 1-3 days post therapy. For measurements post therapy, the gamma camera was operated in the high-count rate mode with appropriate correction factors to compensate for any count loss. A further 16 patients were given iodine-123 iodide (200 MBq) as the diagnostic agent and uptake was measured at 24 h. The ablation activity was administered 5-47 (median 19) days later and uptake again measured at 24 h. In some cases, a further measurement of uptake was made within the period 1-3 days post therapy. Reduced uptake of the therapeutic administration ( P<0.001) was observed in all 26 patients given diagnostic 131I, with a median value of 32.8% (range 6%-93%) of the uptake in the diagnostic study. In the patients given diagnostic 123I, reduced uptake of the ablative radioiodine was observed in 15 of the 16 patients ( P<0.001), and overall the median value was 58.8% (range 17%-130%) of the diagnostic uptake. In one case the uptake post therapy was increased. The stunning observed in the group given 123I was significantly less ( P<0.001) than in the group given 131I. In the patients given diagnostic 131I, stunning appeared to increase in severity the longer the time interval between the diagnostic and therapeutic radionuclides, for intervals up to 25 days. Thereafter, there seemed to be some recovery of uptake capability. Overall there was no evidence of a large rapid loss of radionuclide from the thyroid bed 1-3 days post therapy. The stunning observed using 123I could not be explained by errors in the estimation of relative uptake due to different tissue absorption of the 131I and 123I photons, nor by the radiation dose delivered by the 123I. However, the ablative 131I itself may cause stunning because the cumulated activity, over the first few hours of uptake, is not insignificant when compared with all the cumulated activity from a diagnostic administration of 131I. The resultant radiation dose to the thyroid remnant, as the therapeutic radioiodine is being taken up, may be sufficient to inhibit the uptake process, thus leading to a reduction in maximum uptake when compared with that of a diagnostic activity of radioiodine.     

Recombinant human thyrotropin (rhTSH) in the management of differentiated thyroid cancer

Recombinant human thyrotropin (rhTSH) has been evaluated in 38 patients with differentiated thyroid cancer. The patients had all been treated previously by operation and 31 had received radioiodine 131I. The patients continued to take thyroid hormone and changed to a low iodine diet for 14 days before and throughout the week of testing. The rhTSH was injected intramuscularly on two consecutive days, 74 MBq 131I was administered on the next day and scintigraphy completed 48 h after that. TSH was measured before administration of 131I, and thyroglobulin after the scan. All patients preferred this method to withdrawal of thyroid hormone, but 45% had mild symptoms including headache and nausea. The average TSH was 127 mU x l(-1), and was inversely related to the weight of the patients. Thirty-four had negative scans with a mean uptake of 0.06%. Thyroglobulin values above 10 ng x ml(-1) were found in seven patients, of whom four had similar findings when scanned after withdrawal of thyroid hormone. Of four with positive scans, two had undetectable thyroglobulin. The rate of clearance of 131I was compared in patients studied at 72 h who were hypothyroid and at 48 h in euthyroid patients given rhTSH and was found to be longer in the latter. We conclude that rhTSH can be used to stimulate thyroid tissue to trap 131I and secrete thyroglobulin. Both scan and thyroglobulin should be obtained. The method is well tolerated.     

131I治疗分化型甲状腺癌术后患者疗效影响因素研究

目的 探讨影响分化型甲状腺癌（DTC）患者术后首次131I清除残留甲状腺组织（简称清甲）疗效和多次131I治疗转移灶（清灶）疗效的因素。方法回顾性分析首次接受大剂量清甲治疗的患者46例（分为成功组与未成功组）资料、多次清灶治疗的患者40例（分为临床缓解组和未缓解组）资料,对数据进行t检验、t’检验、X^2检验或Fisher确切概率法筛选影响因素,并做Logistic回归分析。结果用单因素分析筛选出手术方式、残余甲状腺质量、促甲状腺激素（TSH）水平、手术至清甲治疗时间和存在转移灶是影响清甲效果的因素（X2=5．804、t’=-5．258、t=7．376、X^2=8．867、X2=8．615,P均〈0．05）。Logistic回归分析得到的清甲成功的拟合方程为Y=3．766—0．947x,（残余甲状腺质量）-3．149x：（淋巴结转移）-3．373x,（远处转移）。对临床缓解率行单因素分析显示：甲状腺乳头状癌显著高于甲状腺滤泡状癌,仅有淋巴转移灶显著高于有远处转移灶,甲状腺全切显著高于其他手术方式（Fisher确切概率法,X。=7．278,P〈0．05）;首次131I治疗前,临床缓解组的TSH水平明显高于未缓解组,甲状腺球蛋白（Tg）水平明显低于未缓解组（t=4．489、t=-4．906,P均〈0．01）。Logistic回归分析得到清灶成功拟合方程为：Y=-0．363＋0．065x4（TSH水平）-0．250x5（Tg水平）。结论DTC患者首次清甲疗效的影响因素有手术方式、残余甲状腺质量、TSH、手术至清甲治疗时间和有无转移灶;其中残留甲状腺组织少、无淋巴结转移和无远处转移是提高成功率的关键因素。DTC患者清灶疗效的影响因素包括病理类型、手术方式、转移灶的部位、TSH和Tg;其中首次131I治疗前有较高水平的TSH和较低水平的强是提搞缓解率的关键因素。     

Which thyroid cancer patients need periodic stimulation tests?

PURPOSE: Recurrences are frequent in thyroid cancer patients and long-term follow-up is therefore necessary. We evaluated the yield of rhTSH stimulation in three groups of patients, classified according to the UICC/TNM risk stratification and the results of first follow-up testing. METHODS: The study population comprised 129 patients referred for rhTSH testing. All had undergone first follow-up testing after thyroid hormone withdrawal (off-T4) within 1 year of 131I ablation. Negative first follow-up testing was defined as Tg <2 ng/ml and no neck uptake on 131I diagnostic whole-body scan. Seventy-five patients had stage I thyroid cancer and negative first follow-up testing (group A), 19 had stage I disease and positive first follow-up testing (group B), and 35 had stage II-IV disease (group C). RhTSH stimulation was performed an average of 6 years after first follow-up testing. RESULTS: 131I diagnostic scanning after rhTSH was negative in all 75 group A patients. Only one group A patient had detectable Tg after rhTSH injection (1.5 ng/ml), but Tg had also been detected at baseline in this patient (1.45 ng/ml). Given the absence of a response to stimulation, suggesting an interference, Tg was reassessed with a different technique and proved to be undetectable (<0.1 ng/ml). Stimulation with rhTSH in group B showed residual Tg in seven patients and residual 131I uptake in the thyroid bed in two patients, but none of these patients had signs of disease progression. Five group C patients (14%) had a positive rhTSH test result, and this was suggestive of disease progression in at least two cases. CONCLUSION: The first follow-up testing is essential for prognostic classification after 131I ablation of thyroid cancer. In stage I patients, undetectable Tg and negative 131I scan 1 year after ablation define a large population of subjects who have a very low risk of recurrence and who do not require further stimulation tests. In contrast, periodic rhTSH stimulation tests appear useful in higher-risk patients.     

Follow-up of differentiated thyroid cancer

The aim of post-surgical follow-up for differentiated thyroid carcinoma is the early identification of the small proportion of patients who have residual disease or develop a recurrence. When total thyroidectomy and radioiodine ablation have been the initial treatment, three powerful tools are available for the follow-up: basal and TSH-stimulated serum thyroglobulin (Tg) measurement, iodine-131 whole body scan (WBS) and neck ultrasound. Serum Tg measurement is the most sensitive and specific marker of differentiated thyroid cancer. Undetectable serum Tg levels are found in the large majority of disease-free patients, while elevated concentrations of serum Tg are associated with the presence of residual or metastatic thyroid tissue. In the last case, WBS under TSH stimulation (either after withdrawal of L-thyroxine therapy or after recombinant human TSH stimulation) and neck ultrasound are the most informative tests for the detection of distant or local metastases, respectively, that require more appropriate treatment (surgery and/or radioiodine therapy). Using this strategy, most patients will achieve definitive cure and will have a normal quality of life.     

Diagnostic I–131 scintigraphy in patients with differentiated thyroid cancer: No additional value of higher scan dose

OBJECTIVE: After initial treatment with total thyroidectomy and radioiodine ablation, most follow-up protocols for patients with differentiated thyroid carcinoma contain cyclic diagnostic I-131 imaging and serum thyroglobulin measurements. The applied diagnostic I-131 doses vary between 37 and 370 MBq. The aim of this study was to determine the yield of a diagnostic scan with 370 MBq I-131 in patients with a negative diagnostic scan with 74 MBq I-131. METHODS: Retrospective evaluation of 158 patients who received a high-dose diagnostic scan with 370 MBq I-131 because of a negative low-dose diagnostic scan with 74 MBq I-131. Special attention was paid to the patients with positive high-dose diagnostic scanning and undetectable serum thyroglobulin levels after thyroid hormone withdrawal. RESULTS: In 127 (80%) of patients the 370 MBq I-131 scan was negative, just like the preceding low-dose scan. In 31 (20%) of patients abnormal uptake was present on the 370 MBq diagnostic scan. In 19 of these 31 patients serum thyroglobulin was undetectable. In 15/19 the high-dose diagnostic scan proved either false positive or demonstrated clinically irrelevant minor ablation rests. In only four patients (2.5%) did the high-dose diagnostic scans reveal possibly relevant uptake caused by residual differentiated thyroid cancer. CONCLUSION: In 98% of patients a 370 MBq dose of I-131 for diagnostic WBS had no additional value. The combination of a low-dose diagnostic I-131 scan using only 74 MBq combined with a serum Tg level measurement proved sufficient for correct clinical decision making regarding whether the patient requires additional I-131 therapy.