Surveillance of patients to detect recurrent thyroid carcinoma

BACKGROUND: The purpose of this study was to evaluate the utility of surveillance with annual whole-body iodine-131 (131I) scintigraphy for patients with recurrent thyroid carcinoma. METHODS: The records of patients with thyroid carcinoma were reviewed. The 76 patients included in this study had undergone thyroidectomy and postoperative 131I therapy, and had at least 1 negative whole-body 131I scintigraphy 1 year after 131I therapy. There were 59 females and 17 males (age range, 12-74 years). Surgery consisted of a total thyroidectomy for 84% of patients and a subtotal thyroidectomy for 16%. 131I was administered within 1 month of thyroidectomy and annually thereafter until complete ablation of remaining thyroid tissue occurred. Annual follow-up diagnostic whole-body 131I scintigraphy was performed at Years 1 and 2, and then every 3-5 years. Some patients also had scintigraphy performed in Years 3, 4, and 5. RESULTS: Patients received 1-4 annual administrations of 131I (median, 1). The administered activity per treatment was 30-211 mCi, and the total activity administered that was necessary to achieve complete ablation of functioning thyroid tissue ranged from 30 to 514 mCi (median, 100 mCi). The relapse free survival at both 5 and 10 years was 88%. By definition, all of these patients had a negative 131I scintigraphy at 1 year after their last therapeutic 131I administration. Seven patients had a positive 131I scintigraphy 1 year after the first negative scintigraphy. Two other patients had positive 131I images after 2 consecutive negative annual 131I scintigraphic studies. The predictive value for relapse free survival of 1 negative diagnostic 131I study of these patients was 91% (+/- 0.02), and for 2 consecutive annual negative 131I studies the value was 97% (+/- 0.02); these results were significantly different (P = 0.0197). A stepwise logistic regression analysis was performed in an effort to identify risk factors for disease recurrence after complete ablation. None of the variables assessed--age, gender, tumor histology, tumor size, vascular invasion, capsular invasion, surgical margin status, or lymph node status--was predictive of recurrence after complete ablation. CONCLUSIONS: A single negative 131I scintigraphic study after complete ablation has a lower predictive value for relapse free survival than do two consecutive annual negative studies. Annual 131I imaging is recommended for surveillance until 2 consecutive annual negative studies are obtained, after which repeat imaging at 3-5 years appears to be satisfactory.     

100例分化型甲状腺癌术后131I治疗的疗效及安全性评价

目的：探讨131I在分化型甲状腺癌（differentiated thyroid cancer,DTC）术后清除残留甲状腺组织（清甲）和转移灶（清灶）治疗中的疗效及安全性。方法随机选取100例进行131I清甲及清灶治疗的DTC患者。所有患者治疗前3～4周均停服L-T4,并予以131I（2.96～5.55）×103 MBq清甲治疗;治疗后口服L-T4替代治疗,6个月后复查,根据颈部超声、全身显像及血清甲状腺球蛋白（thyroglobulin,Tg）水平评价131I治疗的效果。结果所有的患者均接受1～3次的131I治疗,共140个疗程,平均每次治疗剂量为4.03×103 MBq,1次131I治疗成功率为67%,2次131I治疗成功率为92%,经131I治疗后患者的Tg转阴率为53.3％;治疗后5例患者出现一过性白细胞下降,治疗前后肝肾功能无明显改变。结论 DTC患者术后尽早进行规范化的131I治疗,具有治疗次数少、清甲成功率高且不良反应少的特点,对预防甲状腺癌的复发有重要的作用。     

Familial nonmedullary thyroid cancer

Opinion statement Familial nonmedullary thyroid cancer is more aggressive than sporadic nonmedullary thyroid cancer. It tends to affect younger patients, and the tumors are often multifocal and bilateral. Histologically, 90% of these tumors are papillary cancers and the remaining are Hürthle cell cancers. We recommend total thyroidectomy to remove all the thyroid tissue, which harbors the genetic defect responsible for the disease (even in low-risk patients) due to the predisposition to develop thyroid cancer and the more aggressive nature of the disease. Careful exploration of the ipsilateral lymph nodes with ipsilateral central neck dissection is encouraged to decrease a high recurrence rate (44%). A complete modified radical neck dissection should be limited to a therapeutic role because there is no clear evidence that this procedure carries any survival benefit. We also recommend that patients receive radioactive iodine ablation postoperatively, including a prophylactic dose (30 mCi) for patients with no evidence of residual uptake on the postoperative iodine 131 whole body scan and in low-risk patients using any of the prognostic scoring systems. Patients should be placed on enough thyroid hormone to suppress thyroid-stimulating hormone (TSH) to approximately 0.1 mL/mL in low-risk patients and to less than 0.1 mL/mL in high-risk patients. Focal metastatic disease in patients with familial nonmedullary thyroid cancer is best dealt with by surgical excision followed by radioactive iodine ablation when appropriate. Redifferentiation therapy has a promising role in patients who have radioactive iodine-resistant tumors. The value of prevention, early detection, and targeted gene therapy once the gene or genes responsible for familial nonmedullary thyroid cancer have been identified cannot be overemphasized.     

Radioiodine ablation of post-surgical thyroid remnants after preparation with recombinant human TSH: why, how and when.

AIMS: The use of recombinant human TSH (rhTSH) represents one of the most exciting innovations in the field of differentiated thyroid cancer (DTC) management, but the use of rhTSH for radioiodine post-surgical thyroid remnant ablation is still controversial. The aim of this review is to provide the reader with an analysis of the literature regarding the use of rhTSH for the radioiodine ablation of post-surgical thyroid remnants. METHODS: We performed a literature search of the most relevant papers in the PubMed database. FINDINGS AND CONCLUSIONS: To date, five prospective studies have been published regarding this topic and there is strong evidence of the effectiveness of rhTSH, at least when high doses of 131I are used. Vice-versa, data regarding the outcome of ablation using low doses (30 mCi) are quite different in the studies published. So the problem of the amount of 131I to be administered and the influence of iodine intake is still open. In fact, the results of some studies suggest that 131I uptake could be particularly dependent on iodine intake during the euthyroid state and when low doses of 131I are used. This could be the reason for the reduced radioiodine uptake observed in other studies. However, also when rhTSH stimulation had produced a reduced iodine uptake, this was at least partially compensated for by an increased half-time in thyroid cells. So rhTSH stimulation appears to have pathophysiological bases which all lead to a powerful destructive effect by 131I on thyroid cells. All the data in the literature appear concordant that rhTSH is safe and associated to a good quality of life and the problem of costs appears negligible when compared to the benefits for the patient. In most cases, the use of rhTSH, for radioiodine ablation of post-surgical thyroid remnants can represent the best therapeutic option that we can offer to the patient.     

Disposition of radioiodine (131)I therapy for thyroid carcinoma in a patient with severely impaired renal function on chronic dialysis: a case report

The aim of this study was to analyze the disposition of radioiodine used for the ablation of thyroid remnants after radical surgery for a differentiated thyroid carcinoma in a patient on chronic hemodialysis in order to deliver the optimal (131)I dose to improve the healing rate in these rare cases and to serve as a useful reference to other health care professionals who might face a similar dilemma. A 50 mCi dose of (131)I was administered orally and dialysis sessions were performed 24, 72 and 144 h after therapy. Patient effluent dialyzate waste samples were collected and blood radioactivity analyses were performed at each dialysis session. The (131)I disposition half-life was 2.7 +/- 0.8 h. The amounts of remnant radioactivity in total body patient were 58.7, 38.9 and 27.1%, respectively, after each of the three dialysis sessions and the effective period calculated was 1.4 days. The extents of water purification in blood were 69.7, 47.9 and 22.7% at the beginning of each dialysis and 37.7, 42.8 and 18.1% at the end of each dialysis. Effective periods of radioiodine for thyroid cancer in a patient on hemodialysis resulted in rapid iodine clearance, thereby reducing the effective radiation dose and promoting the need to use larger treatment doses. Hemodialysis was safe and effective during treatment with radioiodine.     

Randomized trials on radioactive iodine ablation of thyroid remnants for thyroid carcinoma--a critique.

PURPOSE: The dose of radioactive iodine ((131)I) required to ablate thyroid remnants following surgery for differentiated thyroid carcinoma is controversial. Typical administered activities range from less than 30 mCi up to 100 mCi, reflecting local practice and regulations governing allowable outpatient doses. This review examines the available randomized trials designed to assess the optimal ablative dose in this setting. METHODS AND MATERIALS: The authors identified three such trials published in 1987, 1991, and 1996, and critically reviewed them from a scientific and statistical point of view. RESULTS: Two of these studies were small and lacked adequate statistical power to answer the question, and the third was very poorly conducted. Conclusion: In our opinion, the appropriate dose of (131)I for ablation of thyroid remnants remains undetermined.     

Evaluation of the surgical completeness after total thyroidectomy for differentiated thyroid carcinoma.

BACKGROUND: To quantify the rate of patients without thyroid remnants, to identify predictive factors for the absence of residual thyroid tissue and to evaluate number, site, size and function of thyroid remnants after total thyroidectomy for differentiated thyroid carcinoma (DTC). METHODS: Thousand one hundred and seventy-eight patients who underwent total thyroidectomy for DTC were evaluated; 343 patients with lymph node or distant metastases and 115 patients with detectable thyroglobulin autoantibodies (TgAb) were excluded. (131)I ablative treatment (RAI) without preliminary diagnostic (131)I whole body scans (DxWBS), and 24-h (131)I quantitative neck uptake (RAIU test) and thyroglobulin (Tg) off L-T4 evaluation were performed in the remaining 720 pts. In 252 patients a 99mTc-pertechnetate pre-operative thyroid scan (99mTc-scan) was used for comparison with (131)I neck scans after RAI to evaluate site of thyroid remnants. Only patients with thyroid remnants were evaluated for successful ablation 6-10 months after RAI. RESULTS: Post-treatment whole body scan (TxWBS) demonstrated lack of thyroid remnants in 50/720 patients and the best predictive factors for the absence of residual thyroid tissue were RAIU <1% and undetectable Tg off L-T4. Thyroid remnants were present in 670/720 patients. In 252 patients with (99m)Tc-scan, 617 sites of functioning thyroid tissue were found: 381 within and 236 outside the thyroid bed. Complete successful ablation was achieved in 610/670 patients with thyroid remnants. CONCLUSIONS: This study confirms that most patients (93.1%) have thyroid remnant after total thyroidectomy for DTC. Most thyroid remnants were contralateral to tumour site and were even observed outside thyroid bed. However, a real total thyroidectomy, demonstrated by negative TxWBS, RAIU <1% and undetectable Tg off L-T4, was achieved in 6.9% of patients.     

The Na+/I- symporter mediates iodide uptake in breast cancer metastases and can be selectively down-regulated in the thyroid.

PURPOSE: The Na(+)/I(-) symporter (NIS) is a key plasma membrane protein that mediates active iodide (I(-)) transport in the thyroid, lactating breast, and other tissues. Functional NIS expression in thyroid cancer accounts for the longstanding success of radioactive iodide ((131)I) ablation of metastases after thyroidectomy. Breast cancer is the only other cancer demonstrating endogenous functional NIS expression. Until now, NIS activity in breast cancer metastases (BCM) was unproven. EXPERIMENTAL DESIGN: Twenty-seven women were scanned with (99m)TcO(4)(-) or (123)I(-) to assess NIS activity in their metastases. An (131)I dosimetry study was offered to patients with I(-)-accumulating tumors. Selective down-regulation of thyroid NIS was tested in 13 patients with T(3) and in one case with T(3) + methimazole (MMI; blocks I(-) organification). NIS expression was evaluated in index and/or metastatic tumor samples by immunohistochemistry. RESULTS: I(-) uptake was noted in 25% of NIS-expressing tumors (two of eight). The remaining cases did not show NIS expression or activity. Thyroid I(-) uptakes were decreased to 相似文献   

Death from differentiated thyroid carcinoma: retrospective study of a 40-year investigation

Differentiated thyroid carcinoma (DTC) usually has a good prognosis, but sometimes the course of the disease results in death. The aim of the present study was to assess the effect of some variables in time to death on fatal cases in our series. A total of 83 patients with DTC who died between 1958 and 1998 from differentiated thyroid cancer were retrospectively analyzed with respect to gender, age at diagnosis, histology, percentage of (131)I uptake by postoperative thyroid remnant, site of tumor growth, and its (131)I uptake, metastases and time to death. Univariate analysis revealed a significantly shorter time to death in local recurrence when comparing local lymph node metastases and distant metastases even if neither show (131)I uptake. Multivariate analysis revealed that age at diagnosis was the most important factor in conditioning the time to death. In conclusion, in those patients who died from DTC an older age at diagnosis and presence of local recurrence influenced the time to death independently of (131)I uptake.     

Comparison of the effectiveness between a single low dose and fractionated doses of radioiodine in ablation of post-operative thyroid remnants

Due to the lack of radiation isolation wards in most hospitals in Taiwan, high-dose (exceeding 30 mCi) radioiodine therapy is usually performed in a fractionated manner (successively administering multiple low doses). This study compared the ablating efficacies of post-operative thyroid remnants using a single low dose (30 mCi) and fractionated doses (four doses of 30 mCi given at weekly intervals) in 59 patients with differentiated thyroid cancer who received total or near-total thyroidectomy. Successful ablation was obtained in 20 of 38 patients (52.6%) treated with a single low dose compared with 14 of 21 patients (66.7%) treated in a fractionated manner. There was no statistically significant difference between these two treatment protocols (P = 0.296). As the fractionated-dose protocol has the drawbacks of a much longer hypothyroid state and a higher total expense, we suggest that a single low dose is more feasible than fractionated doses for outpatient ablation therapy.     

Implications of mediastinal uptake of 131I with regard to surgery in patients with differentiated thyroid carcinoma

BACKGROUND: Findings of mediastinal uptake of 131I after surgical treatment for differentiated thyroid carcinoma (DTC) are common, especially in young patients. Given the frequency of false-positive findings, a protocol for diagnostic and therapeutic strategies would be useful. With the goal of accurately selecting management strategies, the authors analyzed their data and data found elsewhere in the literature for correlations with the incidence of mediastinal 131I uptake and with treatment for patients exhibiting such 131I uptake. METHODS: All patients with DTC who were treated between 1978 and 2000 at Groningen University Hospital (Groningen, The Netherlands) and who received adjuvant 131I ablation therapy were included in the current analysis, which involved retrospective review of all relevant data. RESULTS: Five hundred four patients with DTC initially underwent total thyroidectomy, with additional 131I ablation performed for 489 of these patients. In 48 of 489 patients (9.8%), 131I uptake was seen in the mediastinum on a posttreatment scan. Analysis of those 48 patients and of cases in the literature demonstrated that serum thyroglobulin levels, risk status, and the presence of thymus on radiologic images were important in the surgical decision-making process. CONCLUSIONS: Mediastinal uptake of 131I on posttreatment scans was found in approximately 10% of patients after total thyroidectomy for DTC. Based on the current data and the data presented in the literature, the authors developed a flow chart for determining appropriate treatment strategies, which included mediastinal dissection for high-risk patients and for patients with serum thyroglobulin levels > 10 ng/mL.     

Comparable Ablation Efficiency of 30 and 100 mCi of I-131 for Low to Intermediate Risk Thyroid Cancers Using Triple Negative Criteria

Background: There is controversy about ablation efficacy of low or high doses of radioiodine-131 (RAI) in patients with differentiated thyroid cancers (DTC). The purpose of this prospective study was to determine efficacy of 30 mCi and 100 mCi of RAI to achieve successful ablation in patients with low to intermediate risk DTC. Materials and Methods: This prospective cross sectional study was conducted from April 2013 to November 2015. Inclusion criteria were patients of either gender, 18 years or older, having low to intermediate risk papillary and follicular thyroid cancers with T1-3, N0/N1/Nx but no evidence of distant metastasis.Thirty-nine patients were administered 30 mCi of RAI while 61 patients were given 100 mCi. Informed consent was acquired from all patients and counseling was done by nuclear physicians regarding benefits and possible side effects of RAI. After an average of 6 months (range 6-16 months; 2-3 weeks after thyroxin withdrawal), these patients were followed up for stimulated TSH, thyroglobulin (sTg) and thyroglobulin antibodies, ultrasound neck (U/S) and a diagnostic whole body iodine scan (WBIS) for ablation outcome. Successful ablation was concluded with stimulated Tg< 2ng/ml with negative antibodies, negative U/S and a negative diagnostic WBIS (triple negative criteria). ROC curve analysis was used to find diagnostic strength of baseline sTg to predict successful ablation. Results: Successful ablation based upon triple negative criteria was 56% in the low dose and 57% in the high dose group (non-significant difference). Based on a single criterion (follow-up sTgand 77% (again non-significant). The ROC curve revealed that a baseline sTg level 7.4 ng/ml had the highest diagnostic strength to predict successful ablation in all patients. Conclusions: We conclude that 30 mCi of RAI has similar ablation success to 100 mCi dose in patients with low to intermediate risk DTC. A baseline sTg 7.4 ng/ml is a strong predictor of successful ablation in all patients. Low dose RAI is safer, more cost effective and more convenient for patients and healthcare providers.     

Clinical outcome of low-risk differentiated thyroid cancer patients after radioiodine remnant ablation and recombinant human thyroid-stimulating hormone preparation

AimRecombinant human thyroid-stimulating hormone (rhTSH) has been approved in Europe as a preparation tool for radioiodine ablation of post-surgical thyroid remnants in patients with low-risk differentiated thyroid cancer (DTC). Published studies report that, both thyroid hormone withdrawal and rhTSH preparation result in similar rates of successful remnant ablation, but few studies have determined the effectiveness of rhTSH preparation on disease recurrence. We sought to determine the clinical outcome, considering both ablation success and disease recurrence, of low-risk DTC patients who underwent ¹³¹I ablation.Materials and methodsThis retrospective study describes the clinical outcome of 100 patients treated with ¹³¹I remnant ablation after preparation with rhTSH. After ablation, patients were classified as in complete remission, as having no evidence of persistent disease, or as having clinical recurrence on the basis of a subsequent diagnostic whole body scan with ¹³¹I, stimulated thyroglobulin and cross-sectional imaging studies.ResultsOverall assessment of ablation success was verified and obtained in 75% of patients (75/100). Considering only patients who underwent a diagnostic whole body scan and stimulated thyroglobulin without interfering anti-thyroglobulin antibody, complete ablation was obtained in 96% of patients (75/78). After a follow-up of about 4 years, 78 patients are in complete remission: 75 with initial ablation success and three who achieved a complete remission during subsequent follow-up. Among the remaining 22 patients, 21 have no clinical evidence of disease (NCED), indicating the inability to verify the complete remission or to detect residual disease, as in patients with positive thyroglobulin antibody, whereas one has persistent disease demonstrated only by stimulated thyroglobulin. No recurrences were observed. Of four patients initially classified as having persistent disease, one obtained a complete remission and two are now considered NCED.ConclusionOur data confirm the favourable outcome, with low rates of recurrence and persistent disease, of patients with low-risk DTC who underwent ¹³¹I ablation after rhTSH. Moreover, our results compare favourably with those reported in the literature in patients prepared with rhTSH, but also in patients prepared with hormone withdrawal.     

A prospective clinical trial to assess the efficacy of radioiodine ablation as an alternative to completion thyroidectomy in patients with differentiated thyroid cancer undergoing sub-total thyroidectomy

We conducted a prospective clinical trial to evaluate whether radioiodine ablation can be an effective alternative to completion thyroidectomy in patients undergoing sub-total thyroidectomy and if yes, the optimum activity of ¹³¹I and frequency of ablation. A total of 85 patients (F-63; M-22) with mean age of 37.9±12.3 years were recruited in this study. The pre-ablation mean 24 hour radioiodine neck uptake, effective half-life, residual thyroid tissue weight and TSH values were 13.9±8.5%, 4.5±0.9 days, 9.6±3.6 g and 11.7±6.4 µIU/ml, respectively. Thyroid tissue was completely ablated in 50 patients (58.8%, 95% CI:50-68%) after mean 1^st administered activity of 32.3±10.7 mCi of ¹³¹I and the cumulative ablation rate was 91.8% after two doses of ¹³¹I. During mean follow-up duration of 49 months no local/distant recurrence has been observed so far in this cohort. It appears that radioiodine ablation may be an attractive alternative to completion thyroidectomy and an activity as low as 35 mCi may achieve reasonable ablation.     

Contemporary considerations in adjuvant radioiodine treatment of adults with differentiated thyroid cancer

Differentiated thyroid cancer (DTC) is the most common endocrine malignancy with a growing incidence worldwide. The initial conventional management is surgery, followed by consideration of ¹³¹I treatment that includes three options. These are termed remnant ablation (targeting benign thyroid remnant), adjuvant (targeting presumed microscopic DTC) and known disease (targeting macroscopic DTC) treatments. Some experts mostly rely on clinicopathologic assessment for recurrence risk to select patients for the ¹³¹I treatment. Others, in addition, apply radioiodine imaging to guide their treatment planning, termed theranostics (aka theragnostics or radiotheragnostics). In patients with low-risk DTC, remnant ablation rather than adjuvant treatment is generally recommended and, in this setting, the ATA recommends a low ¹³¹I activity. ¹³¹I adjuvant treatment is universally recommended in patients with high-risk DTC (a primary tumor of any size with gross extrathyroidal extension) and is generally recommended in intermediate-risk DTC (primary tumor >4 cm in diameter, locoregional metastases, microscopic extrathyroidal extension, aggressive histology or vascular invasion). The optimal amount of ¹³¹I activity for adjuvant treatment is controversial, but experts reached a consensus that the ¹³¹I activity should be greater than that for remnant ablation. The main obstacles to establishing timely evidence through randomized clinical trials for ¹³¹I therapy include years-to-decades delay in recurrence and low disease-specific mortality. This mini-review is intended to update oncologists on the most recent clinical, pathologic, laboratory and imaging variables, as well as on the current ¹³¹I therapy-related definitions and management paradigms, which should optimally equip them for individualized patient guidance and treatment.     

Predictive value of thyroglobulin changes for the efficacy of thyroid remnant ablation.

The aim of this case-control study was to determine the utility of the evaluation of changes in serum thyroglobulin (Tg) levels before and after 1311 diagnostic total body scan (TBS) in patients with thyroid cancer to predict the efficacy of radioiodine ablation. Among 134 consecutive patients with differentiated thyroid carcinoma (DTC) who had undergone a thyroidectomy and TBS prior to radioiodine ablation, we selected those subjects with no evidence of distant metastases and with two consecutive assessments of Tg before TBS and radioiodine ablation within a period of four weeks. With this selection procedure 27 patients (22 with papillary and five with follicular carcinomas) were included in our evaluation. The ablation therapy was considered successful when the TBS performed one year after treatment did not show any or less than 1% cervical 131I uptake, Tg levels remained below 3 ng/mL, and clinical and instrumental examinations were negative for the presence of relapses. These criteria divided the selected patients into two subsets: patients with successful radioiodine ablation and patients with residual thyroid tissue. The majority of patients with unsuccessful ablation showed an increase in serum Tg levels, while most of the patients with successful ablation showed a steady decrease in Tg concentrations. Statistical analysis evidenced that the increase in Tg levels after TBS was related to unsuccessful ablation (P > or = 0.01). By contrast, the rate of thyroid remnants with 131I uptake did not show any relationship with the outcome of ablation therapy. The group of patients with increasing Tg levels after TBS had a relative risk of 3.3 of unsuccessful ablative therapy compared to the group with stable or decreasing Tg levels. This study supports the concept that by monitoring Tg levels in patients who undergo diagnostic TBS before radioiodine ablation it is possible to obtain useful information about the efficacy of 131I therapy.     

Pulmonary metastases in differentiated thyroid carcinoma. Study of 58 cases with implications for the primary tumor treatment

Fifty-eight cases of pulmonary metastases (PM) from 831 cases of differentiated thyroid carcinoma (DTC) were studied. PM were found in about 10% of follicular and 5% of papillary tumors. 131I uptake was found in 55% of the cases, irrespective of histology. Twenty-one patients were treated by 131I only and 12 were cured. Micronodular metastases, 92% papillary, with 86% positive 131I uptake and 77% 8-year survival rate, are the most favorable forms. In others the influence of PM size/age, uptake, delay of appearance, presence of cervical or mediastinal lymph nodes is discussed. Occurrence of late PM according to treatment of the primary tumor was 1.3% thyroidectomy + 131I; 3% thyroidectomy; 5% partial thyroidectomy + 131I; 11% partial thyroidectomy only. Thus prevention in DTC of severe PM (28% 8-year survival rate) can best be achieved by complete thyroidectomy + 131I ablation dose.     

Comparison of different thyroid committed doses in radioiodine therapy for Graves' hyperthyroidism

Despite vast worldwide experience in the use of 131I for treating Graves' disease (GD), no consensus of opinion exists concerning the optimal method of dose calculation. In one of the most popular equations, the administered (131)I dose is directly proportional to the estimated thyroid gland volume and inversely proportional to the measured 24-hour radioiodine uptake. In this study, we compared the efficiency of different tissue-absorbed doses to induce euthyroidism or hypothyroidism within 1 year after radioiodine therapy in GD patients. The study was carried out in 134 GD patients (age, 53 +/- 14 year; range, 16-82 year; thyroid volume, 28 +/- 18 mL; range, 6-95 mL; average 24-hour thyroid uptake, 72%) treated with (131)I therapy. The average radioiodine activity administered to patients was 518 +/- 226 MBq (range, 111-1110). The corresponding average thyroid absorbed dose, calculated by a modified Medical Internal Radiation Dose (MIRD) equation was 376 +/- 258 Gy (range, 99-1683). One year after treatment, 58 patients (43%) were hypothyroid, 57 patients (43%) were euthyroid, and 19 patients (14%) remained hyperthyroid. The patients were divided into 3 groups: 150 Gy (n = 32), 300 Gy (n = 58) and >300 Gy (n = 44). No significant difference in the rate of recurrent hyperthyroidism was found among the 3 groups (150 Gy: 15%; 300 Gy: 14%; and > or =300 Gy: 14%; chi-square test, p = 0.72). Whereas, the rate of hypothyroidism in the 3 groups was significantly correlated with the dose (150 Gy: 30%; 300 Gy: 46%; >300 Gy: 71%; chi-square test, p = 0.0003). The results obtained in this study show no correlation between dose and outcome of radioiodine therapy (in terms of persistent hyperthyroidism) for thyroid absorbed doses > or =150 Gy, while confirming the relation between the thyroid absorbed dose and the incidence of hypothyroidism in GD patients.     

Thyroid cancer risk after thyroid examination with 131I: a population-based cohort study in Sweden

Ionizing radiation is the only established cause of thyroid cancer, though the effect of diagnostic administration of (131)I on thyroid cancer risk appears minimal. The annual number of thyroid examinations using radioiodine is currently 5 per 1,000 individuals worldwide, so this issue is of public health importance. Our objective was to evaluate the excess risk of thyroid cancer following a range of known doses of (131)I administered for diagnostic purposes. We conducted a nationwide, population-based cohort study in Sweden including all 36,792 individuals who received (131)I for diagnostic purposes during 1952-1969 and were alive and free of thyroid cancer 2 years after exposure. Accrual of person-time at risk commenced 2 years after the first (131)I administration. Follow-up for cancer was to the end of 1998. Standardized incidence ratios (SIRs) were calculated as the ratio between the observed and expected numbers of thyroid cancers. Estimates were stratified by previous exposure to external radiation therapy to the neck, reason for thyroid examination, (131)I dose, sex, age at exposure and time since exposure. Thyroid cancers (n = 129) were diagnosed during 886,618 person-years at risk. Excess thyroid cancers were observed only among the 1,767 patients who reported previous external radiation therapy to the neck [SIR = 9.8, 95% confidence interval (CI) 6.3-14.6] and among those originally referred due to suspicion of a thyroid tumor (SIR = 3.5, 95% CI 2.7-4.4 for 11,015 patients without previous external radiation therapy). The 24,010 patients without previous exposure to external radiation therapy to the neck who were referred for a reason other than suspicion of a thyroid tumor received an estimated dose to the thyroid of 0.94 Gy. Among these patients, 36 thyroid cancers were observed compared to 39.5 expected (SIR = 0.91, 95% CI 0.64-1.26). We found no evidence that administration of (131)I for diagnostic purposes increases risk of thyroid cancer. However, our study included few patients under age 20, so the results apply primarily to exposure among adults. Our data suggest that protraction of dose may result in a lower risk than brief X-ray exposure of the same total dose.     

甲状腺球蛋白抗体对甲状腺乳头状癌131I清甲疗效的影响

背景与目的：甲状腺球蛋白抗体(thyroglobulin antibody,TgAb)在甲状腺乳头状癌(papillary thyroid carcinoma,PTC)中较为常见。该研究旨在探讨PTC患者术后TgAb对¹³¹I清甲疗效的影响。方法：纳入329例非远处转移性PTC患者,根据¹³¹I清甲前TgAb水平分为G1组(大于115 U/mL,n=84)和G2组(<115 U/mL,n=245),G2组再以40 U/mL为界分为S1(大于40 U/mL,n=31)和S2(小于40 U/mL,n=214)两个亚组,中位随访时间24个月,比较两组患者清甲疗效并分析其影响因素,观察¹³¹I清甲剂量对患者疗效的影响。结果：G1组女性居多,年龄更小(P=0.000,P=0.004),其余临床病理基线资料差异均无统计学意义(P均>0.05)。G1组清甲成功率为35.7%,G2组为72.7%,差异有统计学意义(P=0.000);S1和S2两个亚组清甲成功率分别为54.8%和75.2%,差异有统计学意义(P=0.017);G1组高、低剂量¹³¹I清甲后成功率分别为34.1%、37.2%,与G2组的71.9%、73.2%差异均有统计学意义(P均=0.000);G1组与G2组内分别采用低剂量¹³¹I与高剂量¹³¹I清甲的成功率差异均无统计学意义(P均>0.05)。多因素分析显示,清甲疗效仅与清甲前TgAb值有关(P=0.018)。结论：TgAb可以影响PTC患者的¹³¹I清甲疗效,TgAb越高者清甲疗效越差。增加¹³¹I治疗剂量未能进一步提高患者的清甲成功率。