Efficacy of i ablation therapy using different doses as determined by postoperative thyroid scan uptake in patients with differentiated thyroid cancer

PURPOSE: The optimal dose of I(131) for ablation of functioning residual thyroid tissue after surgery is controversial. The current study was conducted to determine the optimal dose of I(131) for remnant postoperative ablation. A review of the literature is included. METHODS AND MATERIALS: A total of 238 patients with papillary and follicular carcinoma were treated with I(131) for ablation of a postoperative thyroid remnant. The I(131) dose was based on the 24-h percentage of neck uptake in the postoperative thyroid scans. Patients with < 5% uptake received a median of 85 mCi; 6-10% uptake, a median of 80 mCi; 11-15% uptake, a median of 60 mCi; 16-20% uptake, a median of 50 mCi; and > or =21% uptake, a median of 30 mCi. The ablation results were compared with the prognostic factors. RESULTS: Complete ablation was observed in 40 (92%) of 43 patients receiving 85 mCi, in 31 (94%) of 33 who received 80 mCi, in 39 (95%) of 41 who received 60 mCi, in 51 (93%) of 55 who received 50 mCi, in 37 (94%) of 39 who received 30 mCi, and in 18 (96%) of 19 who received 30 mCi. The overall successful ablation rate was 94% (95% confidence interval, 89-100%). CONCLUSION: Our findings suggest that patients with differentiated thyroid cancer can be treated with doses of I(131) according to the percentage of neck uptake of postoperative total body scan, with high complete ablation rates, without exposing patients to higher dose levels of I(131).     

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.     

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.     

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.     

分化型甲状腺癌术后首次不同剂量131I清除残留甲状腺组织的临床观察

目的 探讨分化型甲状腺癌术后首次不同剂量131 I清除残留甲状腺组织(清甲)的临床效果.方法 将84例分化型甲状腺癌患者随机分为观察组(131I清甲剂量>100 mCi)和对照组(131I清甲剂量≤100 mCi)各42例.观察组空腹一次性口服131 I 100~120 mCi,对照组空腹一次性口服131 I 30~40 mCi.清甲半年后行131 I甲状腺显像检查,对两组清甲成功率进行评价,并检测促甲状腺激素(TSH)、甲状旁腺素(PTH)和甲状腺球蛋白(TG)水平,以及两组不良反应发生情况.结果 观察组乳头状癌与滤泡状癌清甲成功率与对照组比较,差异无统计学意义(P>0.05).同组内乳头状癌与滤泡状癌清甲成功率比较,差异无统计学意义(P>0.05).清甲前血清TSH浓度≥30 mIU/mL与血清TSH浓度﹤30 mIU/mL比较,差异具有统计学意义(P<0.05).清甲前血清Tg值﹤30 ng/mL与血清Tg值≥30 ng/mL比较,差异具有统计学意义(P<0.05).清甲6个月后,观察组TSH和PTH水平均显著高于对照组,Tg水平显著低于对照组,差异具有统计学意义(P<0.05).对照组胃肠道反应及泪腺功能紊乱发生率均低于观察组,差异具有统计学意义(P<0.05).对照组唾液腺功能紊乱及颈部疼痛发生率与观察组比较,差异无统计学意义(P>0.05).结论 分化型甲状腺癌术后首次应用131 I与剂量无太大关系,且低剂量的不良反应少于高剂量,低剂量131 I方案值得推广.     

Phase I/II trial of (131)I-MN-14F(ab)2 anti-carcinoembryonic antigen monoclonal antibody in the treatment of patients with metastatic medullary thyroid carcinoma

BACKGROUND: Monoclonal antibodies (MAbs) against carcinoembryonic antigen (CEA) have been recognized as targeting agents for medullary thyroid carcinoma (MTC). This Phase I/II study was initiated to determine the safety, maximum tolerated dose (MTD), and therapeutic potential of (131)I-MN-14 F(ab)2 anti-CEA MAb for patients with metastatic MTC. METHODS: Fifteen patients were enrolled in this study. Dose escalation was based on estimates of radiation dose to the bone marrow, and the radioactive dose given was determined by a pretherapy diagnostic study in which 8 mCi (0.6-20 mg) of (131)I-MN-14 F(ab)2 was administered 1 week prior to therapy. RESULTS: Three patients received an initial dose of 140 centigray (cGy) to bone marrow, 11 received 180 cGy, and 1 received 220 cGy. Myelosuppression was the only significant treatment-related dose-limiting toxicity (DLT), and the MTD appeared to be 180 cGy to the bone marrow. Human antimouse antibodies (HAMA) developed in 8 patients 2-6 weeks after therapy. Seven patients had a median of 55% reduction of tumor markers. One patient showed a dramatic improvement in the mass effect on the airways caused by 3 tumor lesions in the neck, with a 45% reduction of overall tumor burden. The disease has continued to be radiologically stable in 11 of 12 assessable patients for periods ranging from 3+ to 26+ months. CONCLUSIONS: Therapy with (131)I-MN-14 F(ab)2 is well tolerated and shows evidence of biochemical and radiologic antitumor activity. HAMA development suggests that humanized MAbs will be required in trials with repeated dose schedules. Further dose escalation, alone or in combination with other therapy modalities, is indicated for future trials, preferably with humanized anti-CEA MAbs.     

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   

Tumors after radiotherapy for thyroid cancer. A case-control study within a cohort of thyroid cancer patients.

A case-control study of Swedish thyroid cancer patients was conducted to evaluate the possible influence of 131I treatment and external radiotherapy on the risk of developing a subsequent cancer. Both cases and controls derived from a cohort of Swedish thyroid cancer patients treated with 131I (n = 834) or by other means (n = 1,121). Thirty-six breast, 13 stomach, 12 kidney, and 5 bladder cancers were found more than 2 years after 131I treatment/thyroid cancer diagnosis. Individual, absorbed dose in the organs was calculated by using ICRP tables, administered activity of 131I, and 24-h 131I uptake. In studying the effect of 131I and external radiotherapy no statistically significant dose-response relationships were found for cancers of the breast, stomach, bladder or kidney. When the absorbed dose from 131I was analyzed separately the risks remained essentially the same. The present follow-up time and the relatively low absorbed dose that the patients received from 131I and external radiotherapy necessitate studies with a longer follow-up time or a larger patient material before more firm conclusions can be made.     

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.     

Options for radionuclide therapy: from fixed activity to patient-specific treatment planning

The therapeutic use of radioisotopes in medicine as unsealed sources has a long history dating back to the 1930s. The established and continuing objectives are to provide radiation dose to the target tissue at the desired cytotoxic level while avoiding or minimizing toxic effects. Selected radionuclide therapy protocols including 32P for polycythemia vera, 131I for Graves' disease, and 131I for postsurgical ablation of thyroid remnants in the management of differentiated thyroid cancer are presented for historical review with the focus on protocols for administering the radiopharmaceuticals and the role played by dosimetry. The discussion also includes consideration of complications and the assessment of outcome for these diseases. The vista for radionuclide therapy today is reviewed along with the options for determining the administered activity. Patient specific dosimetry encompasses a number of levels ranging from basic measurement of relevant biokinetic parameters and use of standard models to calculate (and extrapolate) radiation dose to sophisticated three-dimensional techniques employing fusion of physiologic and high-resolution anatomic images coupled with advanced 3-D voxel patient representation and Monte Carlo techniques for use in radiation dose calculation. The role of patient specific dosimetry in clinical trials (Phase I, II, III trials) along with its utility in treatment planning, follow-up evaluation, and elucidation of dose-response relationships is discussed. The challenge ahead for those who advocate patient specific dosimetry is to assemble the outcome data and perform the analysis to support this contention.     

Phase I trial of 131I-huA33 in patients with advanced colorectal carcinoma.

PURPOSE: Humanized monoclonal antibody A33 (huA33) targets the A33 antigen which is expressed on 95% of colorectal cancers. A previous study has shown excellent tumor-targeting of iodine-131 labeled huA33 (131I-huA33). Therefore, we did a phase I dose escalation trial of 131I-huA33 radioimmunotherapy.Experimental Designs: Fifteen patients with pretreated metastatic colorectal carcinoma each received two i.v. doses of 131I-huA33. The first was an outpatient trace-labeled "scout" dose for biodistribution assessment, followed by a second "therapy" dose. Three patients were treated at 20, 30, and 40 mCi/m2 dose levels, and six patients at 50 mCi/m2 to define the maximum tolerated dose. RESULTS: Hematologic toxicity was 131I dose-dependent, with one episode of grade 4 neutropenia and two episodes of grade 3 thrombocytopenia observed at 50 mCi/m2. The maximum tolerated dose was determined to be 40 mCi/m2. There were no acute infusion-related adverse events, and gastrointestinal toxicity was not observed despite uptake of 131I-huA33 in bowel. Seven patients developed pruritus or rash, which was not related to 131I dose. There was excellent tumor-targeting of 131I-huA33 shown in all patients. The serum T1/2beta of 131I-huA33 was (mean +/- SD) 135.2 +/- 46.9 hours. The mean absorbed tumor dose was 6.49 +/- 2.47 Gy/GBq. Four patients developed human anti-human antibodies. At restaging, 4 patients had stable disease, whereas 11 patients had progressive disease. CONCLUSION: Radioimmunotherapy using 131I-huA33 shows promise in targeting colorectal tumors, and is deliverable at a maximum tolerated dose of 40 mCi/m2. Further studies of 131I-huA33 in combination with chemotherapy are planned.     

Follicular carcinoma of the thyroid gland: prognostic factors, treatment, and survival

Prognostic variables and treatment outcomes of 82 patients treated at the Northern Israel Oncology Center were reviewed. There were 59 women and 23 men in this series. The female/male ratio was 2.6/1. Median age was 46 years. Median follow-up was 11.4 (range: 3.8-24 years). Median tumor size was 3.6 cm. When first seen, 4 patients had lymph node involvement and 11 (13%) had distant metastases. Surgical treatment was total thyroidectomy in 37 patients (45%), subtotal thyroidectomy in 38 (46%), and lesser procedures in 7 (9%). Sixty-six patients (80%) were treated after surgery with 131I to ablate thyroid remnants. Doses ranged between 30 and 80 mCi. The 20-year overall actuarial survival rate was 65%. The actuarial survival rate of patients <40 years of age was 96% versus 33% in patients >50 years of age (p = 0.0008). Patients with distant metastases at presentation had inferior survival compared with patients without metastases. In conclusion, we found subtotal thyroidectomy followed by 131I and hormone therapy to provide survival similar to that with total thyroidectomy, with less morbidity. Risk factors include: age > or =40 at the time of diagnosis, presence of distant metastases, capsular invasion, tumor size > or =2 cm, and male gender.     

分化型甲状腺癌术后131I清甲疗效相关影响因素分析

目的:探讨分化型甲状腺癌术后131I清甲疗效相关影响因素。方法:回顾性分析分化型甲状腺癌术后131I清甲治疗患者128例临床资料,总结包括年龄、性别、病理分型、手术切除方式、肿瘤转移、肿瘤转移部位、血清促甲状腺激素（TSH）水平及131I治疗时间等临床特征对疗效的影响。结果:对不同性别、年龄、病理分型及肿瘤转移有无进行分组比较,分化型甲状腺癌患者术后131I治疗临床疗效差异无统计学意义（P＞0.05）;而行甲状腺全切、肿瘤颈部淋巴结转移、血清TSH水平20~40mIU/L及131I治疗时间≤6个月组分化型甲状腺癌患者术后131I清甲临床疗效显著优于其他分组,差异有统计学意义（P＜0.05）;手术切除方式、血清TSH水平及131I治疗时间是影响分化型甲状腺癌术后131I治疗效果独立因素。结论:分化型甲状腺癌术后131I清甲疗效与手术切除方式、血清TSH水平及131I治疗时间具有相关性。     

分化型甲状腺癌术后首次131I治疗时间选择对疗效的影响

目的:探讨分化型甲状腺癌（DTC）术后首次131I治疗时间选择对疗效的影响。方法:回顾性分析2013年5月至2017年2月于中山大学附属第三医院首次接受131I治疗的DTC患者329例。根据2013年国内131I治疗分化型甲状腺癌指南，131I治疗剂量为30~200 mCi，131I治疗后6个月行疗效评估，疗效分为临床治愈、好转、稳定、进展。根据2015版ATA指南将131I治疗前患者分为中危、高危；按手术与131I治疗时间间隔分为四组:A组（＜1个月）、B组（1~3个月）、C组（＞3~6个月）、D组（＞6~12个月）。分析四组不同时间间隔的DTC患者疗效是否有差异。采用χ2检验、Fisher确切概率法分析数据。结果:各组中年龄及性别构成比等无显著性差异。中危DTC患者中不同时间间隔的四组疗效无差异（P=0.937）。高危DTC患者中不同时间间隔的四组疗效有差异（P=0.017），D组的疗效差于其他各组，其余各组间疗效无差异。结论:中危DTC患者手术后12个月内行首次131I治疗时间间隔对疗效影响不大。高危DTC患者中时间间隔＞6~12个月组的疗效较其他组差，建议高危DTC患者宜在手术后6个月内进行首次131I治疗。     

老年甲状腺癌患者131Ⅰ治疗前后白细胞、粒细胞、单核细胞及淋巴细胞水平变化

目的 探讨老年甲状腺癌患者进行131Ⅰ治疗对白细胞、粒细胞、单核细胞及淋巴细胞的影响.方法 选取接受131Ⅰ治疗的老年甲状腺癌患者90例,对比131Ⅰ治疗前后患者的白细胞、粒细胞、单核细胞及淋巴细胞水平变化.根据病理类型,将纳入患者分为乳头状癌组(64例)和滤泡状癌组(26例);根据131I治疗剂量,将纳入患者分为低剂量组(100 mCi,58例)和高剂量组(150 mCi,32例).结果 治疗后10天,乳头状癌组和滤泡状癌组患者白细胞、粒细胞、单核细胞、淋巴细胞水平比较,差异无统计学意义.治疗后10天,乳头状癌组和滤泡状癌组患者白细胞、粒细胞水平较治疗前上升;淋巴细胞水平较治疗前下降;单核细胞水平治疗前后未明显改变.治疗后10天,低剂量组和高剂量组患者白细胞、粒细胞、单核细胞、淋巴细胞水平比较,差异无统计学意义.治疗后10天,低剂量组和高剂量组患者白细胞、粒细胞水平较治疗前上升;淋巴细胞水平较治疗前下降;单核细胞水平治疗前后未明显改变.治疗后3个月所有患者的白细胞、粒细胞、单核细胞和淋巴细胞水平均恢复正常.结论 131Ⅰ治疗老年甲状腺癌,短期内会导致患者外周血白细胞、粒细胞水平上升,淋巴细胞水平下降,单核细胞水平基本无改变,这一改变为一过性,不受甲状腺癌病理类型、131Ⅰ治疗剂量的影响.治疗3个月后,患者外周血各项指标恢复正常.     

Iodide-induced thyrotoxicosis in a thyroidectomized patient with metastatic thyroid carcinoma

An unusual case of iodide-induced thyrotoxicosis is documented in this article. The patient was a 64-year-old euthyroid man with acromegaly. He also had multiple follicular and papillary thyroid carcinomas with a metastatic lesion in the lumbar vertebrae. After a total thyroidectomy, he became slightly hypothyroid, and the lumbar lesion began to incorporate 131I by scintigraphy. When an iodine-containing contrast medium happened to be injected, a transient increase of serum thyroid hormone level was observed. After complete thyroid ablation with 83 mCi of 131I, the oral administration of 100 mg of potassium iodide for 7 days induced a prominent increase of serum thyroid hormone level. These findings indicated that the metastatic thyroid carcinoma could produce excess thyroid hormone insofar as a sufficient amount of iodide was given. Although this is the first report of such a case, iodide-induced thyrotoxicosis may not be rare in patients with thyroid carcinomas because the Wolff-Chaikoff effect is thought to be lost, and the organic iodinating activity and lysosomal protease activity are well-preserved.     

Cancer risks after diagnostic doses of 131I with special reference to thyroid cancer

Between 1951 and 1969 a total of 35,074 patients less than 75 years of age (mean = 44 years) were examined with diagnostic doses of 131I. The mean administered activity of 131I was 52 microCi and the radiation dose to the thyroid gland was on the average of 0.5 Gy. The cohort was matched with the Swedish Cancer Register for the years 1958-1984. During this period, 3746 cancers occurred more than 5 years after the 131I examination, and the resulting standardized incidence ratio (SIR) was 1.01 (95% confidence interval [CI] = 0.98 to 1.04). SIR for thyroid cancer was 1.18 (95% CI = 0.88 to 1.56). The risks for both cancer of all sites and for thyroid cancer were highest 5 to 9 years after examination (SIR = 1.07 and 2.06, respectively) and did not differ from unity thereafter. With greater than or equal to 10 years of follow-up, risk was not statistically associated with the dose of 131I.     

Chronic myeloid leukemia in a man with papillary carcinoma of the thyroid treated with radioactive iodine

Leukemia as a second malignancy after treatment of thyroid cancer is rare. Most cases reported in the literature have occurred after cumulative doses higher than 800 mCi and it is most commonly acute leukemias. We report a case of chronic myeloid leukemia (CML) occurring in a 40-year-old man 14 years after treatment of papillary thyroid carcinoma. Our patient had the longest interval between the diagnosis of CML and administration of 131I.