Functional results of radioiodine therapy with a 300-GY absorbed dose in Graves' disease

The aim of this study was to assess the results of high-dose radioiodine therapy given to 43 patients with recurrent hyperthyroidism due to Graves' disease between 1986 and 1992. We chose an intrathyroidal absorbed dose of 300 Gy and determined the applied activity individually, which ranged from 240 to 3120 MBq with a median of 752 MBq. Hyperthyroidism was eliminated in 86% of cases after 3 months and in 100% after 12 months. No patient required a second radioiodine treatment. The incidence of hypothyroidism was 63% after 3 months and 93% after 18 months. Neither the pretherapeutic thyroid-stimulating immunoglobulin level nor the degree of co-existing endocrine ophthalmopathy was correlated with the time at which hypothyroidism developed. Patients with previous radioiodine therapy developed hypothyroidism earlier than patients with previous thyroid surgery. The results show that ablative radioiodine therapy with a 300-Gy absorbed dose is a very effective treatment of hyperthyroidism in Graves' disease, but it should be restricted to patients with recurrent hyperthyroidism combined with severe co-existing disorders or episodes of unfavourable reactions to antithyroid drugs. Correspondence to: U.F. Willemsen     

Improved prediction of therapeutic absorbed doses of radioiodine in the treatment of thyroid carcinoma.

We proposed an alternative to a monoexponential model of radioiodine kinetics to obtain a more accurate estimate of absorbed doses to postsurgical thyroid remnants. We suggested that part of the difference between the predicted and the actually absorbed therapeutic doses of (131)I, usually explained by radiation damage of thyroid cells, can be attributed to errors resulting from inadequate sampling of data and oversimplified modeling. METHODS: A standard monoexponential model and alternative biphasic model (incorporating both radioiodine uptake and clearance) were used on 2 sets of patient data to fit time-activity measurements after administration of diagnostic and therapeutic activities of radioiodine. One set of data consisted of 633 records of routine measurements, and the second set consisted of 71 prospectively collected records with measurements performed more frequently and for a longer time. The time-activity curves derived from the 2 models were used to calculate residence times for diagnostic and therapeutic activities of (131)I, and the respective residence times were compared using the paired t test. Errors of fitting and prediction of therapeutic time-activity data were also calculated. RESULTS: With both models, a statistically significant difference (P < 0.01) was found between residence times after diagnostic administration of (131)I and residence times after therapeutic administration of (131)I. However, the effects of biphasic modeling and of improved sampling substantially reduced the difference (P < 0.01). Errors of fitting and prediction were smaller with the biphasic model than with the monoexponential model (P < 0.01). CONCLUSION: The biphasic model more accurately predicts (131)I kinetics when applied to measurements in the short interval after diagnostic administration of radioiodine. The minimum requirement for the biphasic model is measurement twice a day at intervals > 6 h for at least 3 d after administration.     

The treatment of benign thyroid disease

The treatment of benign forms of thyroid disease is reviewed. Endemic goiter is a public health problem preventable by the addition of iodine to the food or water supply. Endemic and familial goiters are treated with replacement doses of I-thyroxine, as are sporadic colloid goiters and goiters resulting from chronic thyroiditis. Hyperfunctioning autionomous nodules without thyrotoxicosis and cystic nodules require no specific therapy. Prophylaxis against diffuse or nodular goiter after radiation to the head or neck for therapeutic purposes with thyroxine replacement therapy is debatable. All forms of hypothyroidism, including incipient types, require replacement thyroxine therapy, but this should be undertaken cautiously in older patients and in those with evidence of ischemic myocardial disease. Myxedema coma requires vigorous treatment and detailed supervision because of dismal mortality rates. Iodine 131 is the treatment of choice in diffuse toxic goiter, but alternative forms.     

Iodine-131 treatment of thyroid cancer: absorbed dose calculated from post-therapy scans

The radiation absorbed dose for nine neck lesions distributed among four thyroid-cancer patients was measured directly from images taken after administration of a treatment dose of 131I. The tumor volume was measured with anterior plus lateral pinhole images by determining magnification and assuming an ellipsoidal shape. Uptake and effective half-life were determined from serial anterior images by use of a calibration curve. Dose lower limits ranged from 2,400 to 29,900 rad. Response to treatment was judged on the basis of one or more follow-up scans at least 8 mo later. All lesions responded to the therapy administration which ranged from 150 to 175 mCi.     

Outcome and toxicity associated with maximum safe dose radioiodine treatment of metastatic thyroid cancer

PURPOSE: This study was designed to determine the outcomes of patients referred to the authors' nuclear medicine service for dosimetric evaluation and treatment of metastatic thyroid cancer with radioiodine I-131. In addition, the incidence and severity of hematologic toxicity associated with treatment were determined. METHODS: A retrospective review of patients referred for dosimetric evaluation was undertaken for the years 1984 to 2000. Chart reviews were performed for 20 patients treated with at least 80% of the calculated maximum safe dose. Outcomes were evaluated for 15 patients for whom sufficient follow-up information was available. The incidence and severity of hematologic toxicity were determined for 12 of the 20 patients. RESULTS: Outcomes were defined as good, fair, or poor. One third of the patients had good, one third had fair, and one third had poor outcomes. Three patients experienced anemia, but no life-threatening hematologic toxicity was observed in any of the patients. Serum thyroglobulin measurements proved to be an efficacious way to predict outcome. The use of recombinant human thyrotropin appears to have increased the sensitivity of the thyroglobulin measurements. CONCLUSIONS: Radioiodine I-131 treatments produce variable outcomes in patients with advanced disease. Hematologic toxicity is well controlled in patients if dosimetric guidelines are followed. I-131 treatment appeared to retard the progression of metastatic thyroid cancer in 50% of the patients who were not cured. Radioiodine doses may be increased to improve efficacy without associated irreversible toxicity.     

131I治疗分化型甲状腺癌颈部摄碘组织的吸收剂量与疗效分析

目的 评估分化型甲状腺癌（DTC）术后行131I治疗后,甲状腺残余灶、DTC转移灶内照射的吸收剂量与治疗反应的关系。 方法 收集2017年2月至9月中山大学附属第三医院核医学科22例DTC术后行131I治疗的患者,其中男性10例、女性12例,年龄21~59岁,中位年龄39.5岁。在患者服药后多个时间点行131I全身平面显像及局部SPECT/CT显像,测算甲状腺残余灶、DTC转移灶的吸收剂量及患者的平均吸收剂量。按照《2015美国甲状腺协会成人甲状腺结节与分化型甲状腺癌指南》评估患者的治疗后反应。使用Mann-Whitney U检验评估残余灶与转移灶在不同疗效及分组之间的吸收剂量差异,受试者工作特征（ROC）曲线评估吸收剂量预测治疗效果的性能。 结果 100%（28/28）的甲状腺残余灶及34.8%（8/23）的DTC转移灶为完全反应。完全反应的DTC转移灶吸收剂量（M=79.3 Gy）高于未完全反应（M=29.8 Gy）的转移灶（Z=?2.195,P=0.028）。ROC曲线分析提示,DTC转移灶的吸收剂量可用于预测病灶行131I治疗后的疗效反应,曲线下面积达0.783（Z=?2.195,P=0.028）,预测病灶达完全反应的截止值为70.6 Gy。患者平均吸收剂量可预测治疗后病情的缓解状况,曲线下面积达0.823（Z=?2.285,P=0.022）。 结论 DTC转移灶的吸收剂量需要达到足量才可达到治疗完全反应。摄碘组织的吸收剂量与患者平均吸收剂量均可作为碘治疗后治疗反应的预测指标。     

放射性碘在大鼠甲状腺内的滞留模式及剂量估算

为确定放射性碘在甲状腺内滞留模式，观察甲状腺吸收放射性碘后的生物效应，进而评价其辐射危害。方法利用活体测量方法，直接测量两个不同年龄组大鼠甲状腺内１３１Ⅰ的代谢参数。对测量数据进行处理后得到了大鼠甲状腺内１３１Ⅰ的滞留函数为三指数项函数。结果利用所得三指数项滞留函数的准确方法进行剂量估算，所得的两组动物的甲状腺平均累积吸收剂量分别为７．７Ｇｙ和１１．５Ｇｙ，而一般方法算得的大鼠甲状腺的平均累积吸收剂量比用准确方法高估了６６％～９１％。结论由于准确方法考虑到影响估算甲状腺所受剂量的一些因素，故可相对准确地反映了１３１Ⅰ所致不同年龄大鼠甲状腺的吸收剂量。     

The influence of saliva flow stimulation on the absorbed radiation dose to the salivary glands during radioiodine therapy of thyroid cancer using 124I PET(/CT) imaging

Purpose

A serious side effect of high-activity radioiodine therapy in the treatment of differentiated thyroid cancer is radiogenic salivary gland damage. This damage may be diminished by lemon-juice-induced saliva flow immediately after ¹³¹I administration. The aim of this study was to assess the effect of chewing lemon slices on the absorbed (radiation) doses to the salivary glands.

Methods

Ten patients received (pretherapy) ¹²⁴I PET(/CT) dosimetry before their first radioiodine therapy. The patients underwent a series of six PET scans at 0.5, 1, 2, 4, 48 and ≥96 h and one PET/CT scan at 24 h after administration of 27 MBq ¹²⁴I. Blood samples were also collected at about 2, 4, 24, 48, and 96 h. Contrary to the standard radioiodine therapy protocol, the patients were not stimulated with lemon juice. Specifically, the patients chewed no lemon slices during the pretherapy procedure and neither ate food nor drank fluids until after completion of the last PET scan on the first day. Organ absorbed doses per administered ¹³¹I activity (ODpAs) as well as gland and blood uptake curves were determined and compared with published data from a control patient group, i.e. stimulated per the standard radioiodine therapy protocol. The calculations for both groups used the same methodology.

Results

A within-group comparison showed that the mean ODpA for the submandibular glands was not significantly different from that for the parotid glands. An intergroup comparison showed that the mean ODpA in the nonstimulation group averaged over both gland types was reduced by 28% compared to the mean ODpA in the stimulation group (p=0.01). Within each gland type, the mean ODpA reductions in the nonstimulation group were statistically significant for the parotid glands (p=0.03) but not for the submandibular glands (p=0.23). The observed ODpAs were higher in the stimulation group because of increased initial gland uptake rather than group differences in blood kinetics.

Conclusion

The ¹²⁴I PET(/CT) salivary gland dosimetry indicated that lemon juice stimulation shortly after ¹³¹I administration in radioiodine therapy increases the absorbed doses to the salivary glands.     

Radiotherapy for benign disease; assessing the risk of radiation-induced cancer following exposure to intermediate dose radiation

Most radiotherapy (RT) involves the use of high doses (>50 Gy) to treat malignant disease. However, low to intermediate doses (approximately 3–50 Gy) can provide effective control of a number of benign conditions, ranging from inflammatory/proliferative disorders (e.g. Dupuytren''s disease, heterotopic ossification, keloid scarring, pigmented villonodular synovitis) to benign tumours (e.g. glomus tumours or juvenile nasopharyngeal angiofibromas). Current use in UK RT departments is very variable. This review identifies those benign diseases for which RT provides good control of symptoms with, for the most part, minimal side effects. However, exposure to radiation has the potential to cause a radiation-induced cancer (RIC) many years after treatment. The evidence for the magnitude of this risk comes from many disparate sources and is constrained by the small number of long-term studies in relevant clinical cohorts. This review considers the types of evidence available, i.e. theoretical models, phantom studies, epidemiological studies, long-term follow-up of cancer patients and those treated for benign disease, although many of the latter data pertain to treatments that are no longer used. Informative studies are summarized and considered in relation to the potential for development of a RIC in a range of key tissues (skin, brain etc.). Overall, the evidence suggests that the risks of cancer following RT for benign disease for currently advised protocols are small, especially in older patients. However, the balance of risk vs benefit needs to be considered in younger adults and especially if RT is being considered in adolescents or children.