Whole-Body Radioiodine Effective Half-Life in Patients with Differentiated Thyroid Cancer

Background: Radioactive 131I (RAI) therapy is used in patients with differentiated thyroid cancer (DTC) after total thyroidectomy for remnant ablation, adjuvant treatment or treatment of persistent disease. 131I retention data, which are used to indicate the time at which a 131I treated DTC patient can be released from the hospital, may bring some insights regarding clinical factors that prolong the length of hospitalization. The aim of this study was to investigate the 131I whole-body retention in DTC patients during 131I therapy. Methods: We monitored 166 DTC patients to follow the 131I whole-body retention during 131I therapy with a radioactivity detector fixed on the ceiling of each protected room. A linear regression fit permitted us to estimate the whole-body 131I effective half-life in each patient, and a relationship was sought between patients’ clinical characteristics and whole-body effective 131I half-life. Results: The effective 131I half-life ranged from 4.08 to 56.4 h. At multivariable analysis, longer effective 131I half-life was related to older age and extensive extra-thyroid disease. Conclusions: 131I effective half-life during 131I treatment in DTC patients is highly variable among patients and is significantly longer in older and in patients with RAI uptake in large thyroid remnants or in extrathyroidal disease that significantly prolongs the whole-body retention of 131I.

The Influences of TSH Stimulation Level, Stimulated Tg Level and Tg/TSH Ratio on the Therapeutic Effect of 131I Treatment in DTC Patients

PurposeTo study the influences of pre-ablation TSH stimulation level, sTg and sTg/TSH ratio on the therapeutic effect of the first 131I treatment in DTCs.MethodsAccording to the thyroid stimulating hormone (TSH) levels (mU/l), all the 479 differentiated thyroid cancer (DTC) patients were divided into two groups: TSH < 30 and TSH ≥ 30. The TSH ≥ 30 group was divided into three subgroups: 30 ≤ TSH < 60, 60 ≤ TSH < 90 and TSH ≥ 90. The clinical features and the therapeutic effects of the first 131I treatment were analyzed. The cutoffs of stimulated thyroglobulin (sTg) and sTg/TSH ratio were calculated to predict the therapeutic effect of 131I treatment.ResultsAmong the three subgroups, the TSH ≥ 90 subgroup was younger and less likely to be associated with cervical lymph node metastasis (LNM). The postoperative levothyroxine (L-T4) dose in the 60 ≤ TSH < 90 subgroup was the lowest. Between the two groups, patients in the TSH < 30 group had higher postoperative L-T4 dose and longer thyroid hormone withdrawal (THW) time. The excellent response rates six months after the first 131I treatment among the three subgroups and between the two groups were not of statistical significance. The distribution of different TSH stimulation levels among each response group was similar. The cutoffs for the better therapeutic effect of the first 131I treatment in sTg and sTg/TSH were < 9.51 ng/ml and < 0.11, respectively. Both univariate and multivariate logistic regressions showed that cervical LNM, distant metastasis, higher sTg and higher sTg/TSH ratio predicted poorer therapeutic effect.ConclusionsThere was no significant influence of TSH stimulation levels before the first 131I treatment on the therapeutic effect of DTC. The sTg/TSH ratio can be considered as another predictor of 131I therapeutic effect.

Differentiated Thyroid Carcinoma With Metastatic Presentation: 2 Clinical Cases

Introduction: Papillary thyroid carcinoma is the most common endocrine malignancy. Distant metastasis from differentiated thyroid carcinoma is infrequent, usually seen in lungs and bone. The incidence of bone metastasis is 1%-7% in papillary thyroid carcinoma. Hurtlhe cell carcinoma is a rare malignancy of the thyroid gland that can present with local or distant metastases. Main treatment for metastatic well-differentiated thyroid carcinoma includes radioactive iodine (131I) and surgical resection. Clinical case 1: In 2019, a 57 year-old woman, without significant prior medical history, with diffuse upper back and thoracic (10th -12th rib location) pain complaints, for over a year, is submitted to full body bone scintigraphy which reveals a lytic lesion located in the 10th left rib: histology is compatible with metastatic disease, from thyroid follicular carcinoma. Thoracic-abdominal-pelvic computed tomography (CT) has no sign of disease, but thyroid ultrasound shows a left located 24 mm nodule. The patient is submitted to total thyroidectomy and after histology revealed a papillary thyroid carcinoma (follicular variant), 131I treatment takes place (5550 MBq /150 mCi). Post–treatment131I scintigraphy presents with neck foci, in relation with thyroid residual tissue along with intense uptake in a massive lesion around the 10th left rib. Excision of this lesion is decided. The patient remains under clinical and imaging surveillance, being treated with levothyroxine 125 µg and without further complications, until today. Clinical case 2: In 2018, a 78 year-old woman, with prior medical history of hypertension and dyslipidemia, is sent to Neurology practice in the set of diplopia of recent onset. During the evaluation, a thoracic CT reveals a single 4 mm pulmonary lesion and a calcified infracentimetric thyroid nodule. The patient is submitted to bronchofibroscopy and immunohistochemistry of the collected tissue was compatible with metastasis of oncocytic thyroid carcinoma. Thyroid nodule citology is suggestive of Hurthle cell thyroid carcinoma. Total thyroidectomy with central neck lymphadenectomy takes place and histology confirms the diagnosis. After 131I treatment (5550 MBq/150 mCi), 131I scintigraphy reveals 131I uptake foci on the neck, in relation with thyroid residual tissue and a pulmonary uptake focus (known lesion). A second 131I treatment is performed and posterior scintigraphy shows improvement of metastatic disease. The patient remains under clinical and imaging surveillance, being treated with levothyroxine 100 µg and without further complications, until today. Conclusion: These cases reflect the importance of patient complaints in the differential diagnosis, especially osteoarticular complaints, showing that thyroid cancer can present itself already in the metastatic phase and the need to better treat our patients.

Bone Marrow Mesenchymal Stem Cell mediated Ultrasmall Gold Nanoclusters and hNIS Gene Synergize Radiotherapy in Breast Cancer

The human sodium iodide symporter (hNIS) can be linked to the downstream of radiation-sensitive early growth response protein1 (Egr1) promoter, and activated by the Egr1 following 131I treatment. However, the...

Animal Models for the Evaluation of Theranostic Radiopharmaceuticals

Background: Theranostic is a new field of medicine that combines diagnosis and patient-specific targeted treatment. In the theranostic approach, it is aimed to detect diseased cells by using targeted molecules using disease-specific biological pathways and then destroy them by cellular irradiation without damaging other tissues. Diagnostic tests guide the use of specific therapeutic agents by demonstrating the presence of the receptor/molecule on the target tissue. Because the therapeutic agent is administered to patients who have a positive diagnostic test, the efficacy of treatment in these patients is largely guaranteed. As therapeutic efficacy can be predicted by therapeutic agents, it is also possible to monitor the response to treatment. Many diagnostic and therapeutic procedures in nuclear medicine are classified as theranostic. 131I treatment and scintigraphy is the best example of theranostic application. Likewise, 177Lu / 90Y octreotate for neuroendocrine tumors, 177Lu PSMA for metastatic or treatment-resistant prostate cancer, 90Y SIRT for metastatic liver cancer, and 223Ra for bone metastasis of prostate cancer are widely used. Also nanoparticles are one of the most rapidly developing subjects of theranostics. Diagnostic and therapeutic agents that show fluorescent, ultrasonic, magnetic, radioactive, contrast, pharmacological drug or antibody properties are loaded into the nanoparticle to provide theranostatic use. Method: This article will review general aspects of preclinical models for theranostic research, and present examples from the literature. Conclusion: To achieve successful results in rapidly accelerating personalized treatment research of today, the first step is to conduct appropriate preclinical studies.

SUN-510 Prolonged RAIA Induced Thyroiditis After 131 I Therapy for Graves’ Hyperthyroidism

Radioactive iodine ablation (RAI) has been used for the treatment of Graves’ hyperthyroidism since 1946 and it is the primary recommended modality for Graves’ disease treatment in many countries. Acute painful radiation thyroiditis after radioiodine treatment for hyperthyroidism of Graves’ disease is considered uncommon. The prevalence is 1-5% in patients treated with 131I therapy for hyperthyroidism. Dose of RAI and thyroid volume can be precipitating factors for post radiation thyroiditis. The higher RAI dose increases the chance of RAI thyroiditis while the larger goiter size decreases the absorbed radiation dose in the thyroid gland. We present a 25-year-old Emirati male previously healthy, who was referred to our service for hyperthyroidism management. He presented with thyrotoxicosis in absence of goiter. All investigations revealed that graves’ disease is the primary cause of his hyperthyroidism. He was treated with RAI ablation 18.3 mCi. Day four after RAI, he presented with severe pain in the anterior neck associated with fatigue, tremor, palpitation and weight loss. Symptoms lasted for 6 weeks post RAI. There was laboratory evidence of thyrotoxicosis presented with further suppression of TSH and higher fT4 than the baseline. Acute radiation thyroiditis was diagnosed and has been commenced on propranolol 10mg BID. Symptoms completely resolved after 6 weeks of treatment and thyroid function returned to normal level. The patient has remained asymptomatic on continued follow up care till eventually became hypothyroid clinically and biochemically. Our case reflects that radioiodine thyroiditis can last for longer period and occur after larger doses of 131I treatment in absence of goiter. Our patient has RAIA induced thyroiditis lasted for 6 weeks post 18.3mCi of 131I, and has no goiter, which were both contributing factors for RAIA induced thyroiditis