(131)I therapy in patients with benign thyroid disease does not conclusively lead to a higher risk of subsequent malignancies

Changes in Radiosensitivity to Gamma-Rays of Lymphocytes from Hyperthyroid Patients Treated with I-131

This study investigated the peripheral blood lymphocytes (PBL) response to a dose of γ-rays in patients treated with radioiodine (I-131) for hyperthyroidism vs. healthy controls, to gain information about the individual lymphocytes’ radio-sensitivity. Blood samples were taken from 18 patients and 10 healthy donors. Phosphorylated histone variant H2AX (γ-H2AX) and micronuclei (MN) induction were used to determine the change in PBL radio-sensitivity and the correlations between the two types of damage. The two assays showed large inter-individual variability in PBL background damage and in radio-sensitivity (patients vs. healthy donors). In particular, they showed an increased radio-sensitivity in 36% and 33% of patients, decrease in 36% and 44%, respectively. There was a scarce correlation between the two assays and no dependence on age or gender. A significant association was found between high radio-sensitivity conditions and induced hypothyroidism. PBL radio-sensitivity in the patient group was not significantly affected by treatment with I-131, whereas there were significant changes inter-individually. The association found between clinical response and PBL radio-sensitivity suggests that the latter could be used in view of the development of personalized treatments.

Higher thyroid hormone levels and cancer

PURPOSE

This narrative review aims to summarize the relationship between hyperthyroidism, upper reference range thyroid hormone (TH) levels, and cancer, and to address the clinical management of hyperthyroidism in cancer patients.

METHODS

A comprehensive search was performed by an independent reviewer through Google Scholar and PubMed Electronic databases. All searches were restricted to English language manuscripts published between 2000 and 2020.

RESULTS

Numerous in vitro, in vivo, and population-based studies suggest cancer-stimulating effect of triiodothyronine and thyroxin. THs are presented as mediators for tumor growth, proliferation, and progression. Many population and case-control studies suggest an increased risk of several solid but also hematologic malignancies in relation to hyperthyroidism and upper normal range TH levels. However, results are not unambiguous. In this review, we will summarize population and case-control studies that investigated the relationship between hyperthyroidism, upper reference range TH levels, lower thyrotropin (TSH) levels, lower reference range TSH levels with cancer risk, cancer prognosis, and cancer outcome. The vast majority of evidence suggests an association between clinical and subclinical hyperthyroidism with the risk of developing several types of cancer. Furthermore, hyperthyroidism is also linked with a poorer cancer prognosis. In this review, we will also discuss the diagnosis of hyperthyroidism in patients with pre-existing cancer and cover the management of hyperthyroidism in cancer patients, with special attention on the role of nuclear medicine.

CONCLUSIONS

It is crucial to emphasize the importance of the rapid establishment of euthyroidism, and consequently, the importance of radioiodine therapy, as the therapy of choice in most cancer patients. We want to show that in this day and age there still is a high relevance for I-131 to achieve a permanent solution and thus likely reduce the risk of adverse influence of hyperthyroidism on the occurrence of new and course of existing cancer cases.

Percutaneous thermal microwave ablation of thyroid nodules

Microwave ablation (MWA) is a new minimal invasive method for thermal ablation of benign thyroid nodules. In contrast to well-established radiofrequency ablation (RFA), MWA offers several advantages with similarly successful results. There has not been any use of functional imaging with 99mTc-per- technetate and 99mTc-MIBI-scans as a mere qualitative analysis of this imaging in the field of MWA in Europe until now. The aim of this study has been to demonstrate the feasibility of MWA as well as the applicability of functional imaging to verify effectiveness with a centerspecific score. Patients, methods: 11 patients (5 women, 6 men, average age 62.3 years) with 18 benign thyroid nodules were treated. MWA was operated under local anesthesia with a system working in a wavelength field of 902 to 928 MHz (Avecure MWG881, MedWaves, Inc. San Diego, CA). Pre- and postablative scans were controlled by two specialists in nuclear medicine with longtime work experience. Results: A center specific functional imaging score (CSFIS) was defined, a decrease of 1.4 points at an average was noticeable (range 1-3 points). In 66.7% (n = 12) of all nodules the score decreased by 1 point, 27.8% (n = 5) by 2 points and 5.6% (n = 1) by 3 points. The treatment was well tolerated and no severe complications were observed. Conclusion: The preliminary data suggests that MWA is an effective method to treat benign thyroid nodules. Functional imaging is a promising technique for early verification of effectiveness of thermal ablation.

Estimation of Second Primary Cancer Risk After Treatment with Radioactive Iodine for Differentiated Thyroid Carcinoma

BACKGROUND

An increase in the incidence of second primary cancers is the late effect of greatest concern that could occur in differentiated thyroid carcinoma (DTC) patients treated with radioactive iodine (RAI). The decision to treat a patient with RAI should therefore incorporate a careful risk-benefit analysis. The objective of this work was to adapt the risk-estimation models developed by the Biological Effects of Ionizing Radiation Committee to local epidemiological characteristics in order to assess the carcinogenesis risk from radiation in a population of Brazilian DTC patients treated with RAI. Absorbed radiation doses in critical organs were also estimated to determine whether they exceeded the thresholds for deterministic effects.

METHODS

A total of 416 DTC patients treated with RAI were retrospectively studied. Four organs were selected for absorbed dose estimation and subsequent calculation of carcinogenic risk: the kidney, stomach, salivary glands, and bone marrow. Absorbed doses were calculated by dose factors (absorbed dose per unit activity administered) previously established and based on standard human models. The lifetime attributable risk (LAR) of incidence of cancer as a function of age, sex, and organ-specific dose was estimated, relating it to the activity of RAI administered in the initial treatment.

RESULTS

The salivary glands received the greatest absorbed doses of radiation, followed by the stomach, kidney, and bone marrow. None of these, however, surpassed the threshold for deterministic effects for a single administration of RAI. Younger patients received the same level of absorbed dose in the critical organs as older patients did. The lifetime attributable risk for stomach cancer incidence was by far the highest, followed in descending order by salivary-gland cancer, leukemia, and kidney cancer.

CONCLUSION

RAI in a single administration is safe in terms of deterministic effects because even high-administered activities do not result in absorbed doses that exceed the thresholds for significant tissue reactions. The Biological Effects of Ionizing Radiation Committee mathematical models are a practical method of quantifying the risks of a second primary cancer, demonstrating a marked decrease in risk for younger patients with the administration of lower RAI activities and suggesting that only the smallest activities necessary to promote an effective ablation should be administered in low-risk DTC patients.

Clinical and Dosimetric Variables Related to Outcome After Treatment of Graves' Disease With 550 and 1110 MBq of 131I: Results of a Prospective Randomized Trial

: Therapy of Graves' hyperthyroidism (HTG) with I is still mostly performed on an empirical basis. The present study was carried out to evaluate clinical and dosimetric variables associated with outcome in HTG therapy, which could contribute to planning and defining the most appropriate activity to be administered.

METHODS

Patients with HTG were randomly assigned to therapy with 555 MBq (15mci) or 1110 MBq (30 mCi) of I. Estimation of thyroid radiation absorbed dose was made according to MIRD methodology. Success was defined as clinical/laboratory euthyroidism or hypothyroidism one year after therapy. The association between clinical, laboratory, and dosimetric variables with 1-year outcome was measured using bivariate analysis, followed by logistic regression.

RESULTS

Ninety-one patients included completed the follow-up. Therapeutic success was observed in 77 (84.6%) of them, in a greater proportion when 1110 MBq of I was administered as compared with 550 MBq (94.8% vs 77.4%, P = 0.02). Besides administered activity, multivariate analysis indicated that outcome was related to patient age and gland mass. A higher therapeutic success rate was achieved with doses greater than 300 Gy as compared with doses less than 300 Gy (89% vs 60%, P = 0.01).

CONCLUSION

Administered activity, age, and gland mass were related to the outcome. Radiation absorbed dose, although not significant according to multivariate analysis, may be used as a quantitative parameter in therapy planning, with a target dose of 300 Gy. In cases where a rapid and efficient response to radioiodine treatment is required, adoption of a simplified protocol employing high activities is justified.

The Brazilian consensus for the diagnosis and treatment of hyperthyroidism: recommendations by the Thyroid Department of the Brazilian Society of Endocrinology and Metabolism

INTRODUCTION

Hyperthyroidism is characterized by increased synthesis and release of thyroid hormones by the thyroid gland. Thyrotoxicosis refers to the clinical syndrome resulting from excessive circulating thyroid hormones, secondary to hyperthyroidism or due to other causes. This article describes evidence-based guidelines for the clinical management of thyrotoxicosis.

OBJECTIVE

This consensus, developed by Brazilian experts and sponsored by the Department of Thyroid Brazilian Society of Endocrinology and Metabolism, aims to address the management, diagnosis and treatment of patients with thyrotoxicosis, according to the most recent evidence from the literature and appropriate for the clinical reality of Brazil.

MATERIALS AND METHODS

After structuring clinical questions, search for evidence was made available in the literature, initially in the database MedLine, PubMed and Embase databases and subsequently in SciELO - Lilacs. The strength of evidence was evaluated by Oxford classification system was established from the study design used, considering the best available evidence for each question.

RESULTS

We have defined 13 questions about the initial clinical approach for the diagnosis and treatment that resulted in 53 recommendations, including the etiology, treatment with antithyroid drugs, radioactive iodine and surgery. We also addressed hyperthyroidism in children, teenagers or pregnant patients, and management of hyperthyroidism in patients with Graves' ophthalmopathy and various other causes of thyrotoxicosis.

CONCLUSIONS

The clinical diagnosis of hyperthyroidism usually offers no difficulty and should be made with measurements of serum TSH and thyroid hormones. The treatment can be performed with antithyroid drugs, surgery or administration of radioactive iodine according to the etiology of thyrotoxicosis, local availability of methods and preferences of the attending physician and patient.

Radiolabeled Cetuximab Conjugates for EGFR Targeted Cancer Diagnostics and Therapy

The epidermal growth factor receptor (EGFR) has evolved over years into a main molecular target for the treatment of different cancer entities. In this regard, the anti-EGFR antibody cetuximab has been approved alone or in combination with: (a) chemotherapy for treatment of colorectal and head and neck squamous cell carcinoma and (b) with external radiotherapy for treatment of head and neck squamous cell carcinoma. The conjugation of radionuclides to cetuximab in combination with the specific targeting properties of this antibody might increase its therapeutic efficiency. This review article gives an overview of the preclinical studies that have been performed with radiolabeled cetuximab for imaging and/or treatment of different tumor models. A particularly promising approach seems to be the treatment with therapeutic radionuclide-labeled cetuximab in combination with external radiotherapy. Present data support an important impact of the tumor micromilieu on treatment response that needs to be further validated in patients. Another important challenge is the reduction of nonspecific uptake of the radioactive substance in metabolic organs like liver and radiosensitive organs like bone marrow and kidneys. Overall, the integration of diagnosis, treatment and monitoring as a theranostic approach appears to be a promising strategy for improvement of individualized cancer treatment.

Cancer risk after medical exposure to radioactive iodine in benign thyroid diseases: a meta-analysis

Radioiodine-131 ((131)I) is widely used for diagnosis and treatment of benign thyroid diseases. Observational studies have not been conclusive about the carcinogenic potential of (131)I and we therefore conducted a meta-analysis. We performed a literature search till September 2011 which included (131)I as a diagnostic or treatment modality ((131)I for treatment of thyroid cancer was excluded). Data on 64 different organ or organ group subsets comprising 22 029 exposed subjects in the therapeutic cohorts and 24 799 in the diagnostic cohorts in seven studies were included. Outcome was pooled as the relative risk (RR) using both standard and bias adjusted methods. Quality assessment was performed using a study-specific instrument. No increase in overall (RR 1.06, 95% CI: 0.94-1.19), main organ group or combined organ group (four groups known to concentrate (131)I; RR 1.11, 95% CI: 0.94-1.31) risks was demonstrable. Individual organs demonstrated a higher risk for kidney (RR 1.70, 95% CI: 1.15-2.51) and thyroid (RR 1.99, 95% CI: 1.22-3.26) cancers with a strong trend for stomach cancer (RR 1.11, 95% CI: 0.92-1.33). A thyroid dose effect was seen for diagnostic doses. While there is no increase in the overall burden of cancer, an increase in risk to a few organs is seen which requires substantiation. The possible increase in thyroid cancer risk following diagnostic (131)I use should no longer be of concern given that it has effectively been replaced by the use of 99mTc-pertechnetate.

Thyroid cancer in Denmark 1943-2008, before and after iodine supplementation

Thyroid cancer incidence has increased worldwide during the previous decades. In this nationwide study, we aimed to identify the overall incidence of thyroid cancer in Denmark during 66 years (1943-2008) and incidences of the four main histological types of thyroid cancer from 1978 to 2008. Data were obtained from the nationwide Danish Cancer Registry, and we focused especially on the period after implementation of compulsory iodine supplementation, which was established on a national level in 2000. We calculated age-standardized incidence rates per 100,000 person-years, and age-period-cohort models were fitted to describe trends in incidence. To quantify trends in incidence over time, log-linear Poisson models were used to estimate annual percentage change. From 1943 to 2008, 1,947 men (29%) and 4,682 women (71%) were diagnosed with thyroid cancer. The age-standardized incidence increased in both sexes; in men from 0.41 to 1.57 per 100,000 and from 0.90 to 4.11 per 100,000 in women, corresponding to a significant average annual percentage change of 1.7 and 1.8%, respectively. The incidence increased with younger birth cohorts. The rise was almost exclusively caused by papillary carcinomas, and it was particularly present during the last decades of the study period. It cannot be ruled out that iodine supplementation may play a role for the risk of thyroid cancer, but as the strongest increase in incidence began in the years before the implementation, it is likely that improvement in diagnostic modalities increased diagnostic activity, and/or new unknown risk factors are also important contributors to the increase.

Striving for euthyroidism in radioiodine therapy of Graves' disease: a 12-year prospective, randomized, open-label blinded end point study

BACKGROUND

In China, use of radioiodine therapy is problematic because of the need for lifelong levothyroxine substitution. Our aim was to find an optimum dosing strategy for (131)I treatment of hyperthyroidism due to Graves' disease (GD). We attempted to achieve euthyroidism to avoid long-term levothyroxine treatment.

METHODS

Six hundred patients with GD were randomized into five groups, each comprising 120 individuals, to receive an individual (131)I activity selected from five different ascending activity ranges. The ranges were modulated according to a clinical score system. Follow-up was extended over a 12-year time frame. The primary outcomes were euthyroidism, hyperthyroidism, hypothyroidism, and recurrent hyperthyroidism. The secondary endpoint was the accumulated (131)I activity needed to achieve euthyroidism.

RESULTS

Out of 682 screened patients, 600 entered the study in 1997. Five hundred twenty-nine completed the last follow-up visit at the end of the study in 2009. Group 3 was identified as the study arm that received the optimum radioiodine activity, with 71.8% of the patients maintaining a euthyroid status, 5.8% remaining hyperthyroid, and 22.3% becoming hypothyroid by the end of the study. This group received 1.85-4.07 MBq per gram of thyroid tissue (average administered activity 261 ± 162 MBq). Over the 12-year follow-up period, the recurrence rate was 13.6%. The efficacy of (131)I treatment was related to activities modulated by a clinical score (χ(2) = 82.1, p = 0.000).

CONCLUSION

Our protocol effectively treated hyperthyroidism and significantly reduced the hypothyroidism rate. It may be preferable to the intentional induction of permanent hypothyroidism recommended by many experts.