Exposing the thyroid to radiation: a review of its current extent, risks, and implications

Dosimetric evaluation of X-ray examinations of paranasal sinuses in pediatric patients

Objective

To estimate the entrance surface air kerma (K_a,e) and air kerma in the region of radiosensitive organs in radiographs of pediatric paranasal sinuses.

Materials and Methods

Patient data and irradiation parameters were collected in examinations of the paranasal sinuses in children from 0 to 15 years of age at two children's hospitals in the city of Recife, PE, Brazil. We estimated the K_a,e using the X-ray tube outputs and selected parameters. To estimate the air kerma values in the regions of the eyes and thyroid, we used thermoluminescent dosimeters.

Results

The K_a,e values ranged from 0.065 to 1.446 mGy in cavum radiographs, from 0.104 to 7.298 mGy in Caldwell views, and from 0.113 to 7.824 mGy in Waters views. Air kerma values in the region of the eyes ranged from 0.001 to 0.968 mGy in cavum radiographs and from 0.011 to 0.422 mGy in Caldwell and Waters views . In the thyroid region, air kerma values ranged from 0.005 to 0.932 mGy in cavum radiographs and from 0.002 to 0.972 mGy in Caldwell and Waters views.

Conclusion

The radiation levels used at the institutions under study were higher than those recommended in international protocols. We recommend that interventions be initiated in order to reduce patient exposure to radiation and therefore the risks associated with radiological examination of the paranasal sinuses.

Selected single-nucleotide polymorphisms in FOXE1, SERPINA5, FTO, EVPL, TICAM1 and SCARB1 are associated with papillary and follicular thyroid cancer risk: replication study in a German population

Several single-nucleotide polymorphisms (SNPs) have been associated with papillary and follicular thyroid cancer (PTC and FTC, respectively) risk, but few have replicated. After analyzing 17525 tag SNPs in 1129 candidate genes, we found associations with PTC risk in SERPINA5, FTO, HEMGN (near FOXE1) and other genes. Here, we report results from a replication effort in a large independent PTC/FTC case-control study conducted in Germany. We evaluated the best tagging SNPs from our previous PTC study and additionally included SNPs in or near FOXE1 and NKX2-1 genes, known susceptibility loci for thyroid cancer. We genotyped 422 PTC and 130 FTC cases and 752 controls recruited from three German clinical centers. We used polytomous logistic regression to simultaneously estimate PTC and FTC associations for 79 SNPs based on log-additive models. We assessed effect modification by body mass index (BMI), gender and age for all SNPs, and selected SNP by SNP interactions. We confirmed associations with PTC and SNPs in FOXE1/HEMGN, SERPINA5 (rs2069974), FTO (rs8047395), EVPL (rs2071194), TICAM1 (rs8120) and SCARB1 (rs11057820) genes. We found associations with SNPs in FOXE1, SERPINA5, FTO, TICAM1 and HSPA6 and FTC. We found two significant interactions between FTO (rs8047395) and BMI (P = 0.0321) and between TICAM1 (rs8120) and FOXE1 (rs10984377) (P = 0.0006). Besides the known associations with FOXE1 SNPs, we confirmed additional PTC SNP associations reported previously. We also found several new associations with FTC risk and noteworthy interactions. We conclude that multiple variants and host factors might interact in complex ways to increase risk of PTC and FTC.

Diagnostic radiography exposure increases the risk for thyroid microcarcinoma: a population-based case-control study

Thyroid cancer incidence and diagnostic radiography exposures, particularly computed tomography (CT) scanning and nuclear medicine examinations, have increased substantially in the USA. However, very few epidemiologic studies have directly investigated their associations. A population-based case-control study was conducted in Connecticut in 2010-2011, including 462 histologically confirmed incident thyroid cancer cases and 498 population-based controls. Multivariate unconditional logistic regression models were used to estimate the associations between diagnostic radiography and the risk of thyroid cancer, controlling for potential confounding factors. Exposure to any form of diagnostic radiography was associated with an increased risk of well-differentiated thyroid microcarcinoma [tumor size≤10 mm, odds ratio (OR)=2.76, 95% confidence interval (CI): 1.31-5.81]. The highest risk increase occurred with nuclear medicine examinations (excluding cardiology tests and thyroid uptake studies; OR=5.47, 95% CI: 2.10-14.23), followed by chest CT scanning (OR=4.30, 95% CI: 1.66-11.14), head and neck CT scanning (OR=3.88, 95% CI: 1.75-8.63), upper gastrointestinal series (OR=3.56, 95% CI: 1.54-8.21), lower gastrointestinal series (OR=3.29, 95% CI: 1.41-7.66), kidney radiography involving dye injection into a vein or artery (OR=3.21, 95% CI: 1.20-8.54), mammography (OR=2.95, 95% CI: 1.14-7.61), chest radiography (OR=2.93, 95% CI: 1.37-6.29), and abdomen CT scanning (OR=2.54, 95% CI: 1.02-6.30). No significant associations were found between these imaging modalities and thyroid tumors larger than 10 mm. This study provides the first direct evidence that CT scanning and nuclear medicine examinations are associated with an increased risk of thyroid cancer. The novel finding that an array of diagnostic radiography procedures are associated with thyroid microcarcinomas warrants further investigation.

Trends of Thyroid Cancer in Israel: 1980-2012

OBJECTIVES

Thyroid cancer incidence is increasing worldwide, while mortality from thyroid cancer is stable or decreasing. Consequently, survival rates are rising. We describe time trends in the incidence, mortality, and 5-year survival of thyroid cancer in Israel in 1980-2012, in light of the global trends.

METHODS

Israel National Cancer Registry database provided information regarding thyroid cancer incidence and vital status, which enabled computation of survival rates. The Central Bureau of Statistics database provided information on thyroid cancer mortality. Incidence and mortality rates were age-adjusted and presented by population group (Jews/Arabs) and gender. Relative 5-year survival rates which account for the general population survival in the corresponding time period were presented by population group and gender. Joinpoint analyses were used to assess incidence trends over time.

RESULTS

In 1980-2012 significant increases in the incidence of thyroid cancer were observed, with an annual percent change (APC) range of 3.98-6.93, driven almost entirely by papillary carcinoma (APCs 5.75-8.86), while rates of other types of thyroid cancer remained stable or decreased. Furthermore, higher rates of early detection were noted. In 1980-2012, a modest reduction in thyroid cancer mortality was observed in Jewish women (APC -1.07) with no substantial change in Jewish men. The 5-year relative survival after thyroid cancer diagnosis has increased to ≥90% in both population groups and both genders.

CONCLUSIONS

The Israeli secular trends of thyroid cancer incidence (increasing), mortality (mostly stable), and survival (modestly increasing) closely follow reported global trends.

MR Angiographic-Guided Percutaneous Sclerotherapy for Venous Vascular Malformations: A Radiation Dose-Reduction Strategy

We present a new technique using MRA instead of the usual DSA to provide guidance in the treatment of venous vascular malformations. When one performs this embolization procedure, appropriate needle positioning within the malformation must be confirmed before injection of the sclerosing agent to prevent untoward complications. Time-resolved imaging of contrast kinetics-MRA can accurately depict the angioarchitecture of the lesion, which substantially reduces the total radiation dose in these patients who are commonly in the pediatric age group and usually require numerous treatment episodes.

Anthropometric Risk Factors for Differentiated Thyroid Cancer in Young Men and Women From Eastern France: A Case-Control Study

The incidence of thyroid cancer has risen over the past decade, along with a rise in obesity. We studied the role of anthropometric risk factors for differentiated thyroid cancer at the time of diagnosis and at age 20 years in a case-control study conducted in eastern France between 2005 and 2010. The study included 761 adults diagnosed with differentiated thyroid cancer before 35 years of age between 2002 and 2006. They were matched with 825 controls from the general population. Odds ratios were calculated using conditional logistic regression models and were reported for all participants, those with papillary cancer only, and women only. The risk of thyroid cancer was higher for participants with a high body surface area (BSA), great height, or excess weight and for women with a high body fat percentage. Conversely, no significant association was found between body mass index and the risk of thyroid cancer. In the present study, we provide further evidence of the role of BSA and excess weight in the risk of thyroid cancer. These epidemiologic observations should be confirmed by further exploration of the biological mechanisms responsible for the associations of obesity and BSA with thyroid cancer.

Management Guidelines for Children with Thyroid Nodules and Differentiated Thyroid Cancer

BACKGROUND

Previous guidelines for the management of thyroid nodules and cancers were geared toward adults. Compared with thyroid neoplasms in adults, however, those in the pediatric population exhibit differences in pathophysiology, clinical presentation, and long-term outcomes. Furthermore, therapy that may be recommended for an adult may not be appropriate for a child who is at low risk for death but at higher risk for long-term harm from overly aggressive treatment. For these reasons, unique guidelines for children and adolescents with thyroid tumors are needed.

METHODS

A task force commissioned by the American Thyroid Association (ATA) developed a series of clinically relevant questions pertaining to the management of children with thyroid nodules and differentiated thyroid cancer (DTC). Using an extensive literature search, primarily focused on studies that included subjects ≤18 years of age, the task force identified and reviewed relevant articles through April 2014. Recommendations were made based upon scientific evidence and expert opinion and were graded using a modified schema from the United States Preventive Services Task Force.

RESULTS

These inaugural guidelines provide recommendations for the evaluation and management of thyroid nodules in children and adolescents, including the role and interpretation of ultrasound, fine-needle aspiration cytology, and the management of benign nodules. Recommendations for the evaluation, treatment, and follow-up of children and adolescents with DTC are outlined and include preoperative staging, surgical management, postoperative staging, the role of radioactive iodine therapy, and goals for thyrotropin suppression. Management algorithms are proposed and separate recommendations for papillary and follicular thyroid cancers are provided.

CONCLUSIONS

In response to our charge as an independent task force appointed by the ATA, we developed recommendations based on scientific evidence and expert opinion for the management of thyroid nodules and DTC in children and adolescents. In our opinion, these represent the current optimal care for children and adolescents with these conditions.

NADPH oxidase DUOX1 promotes long-term persistence of oxidative stress after an exposure to irradiation

Ionizing radiation (IR) causes not only acute tissue damage, but also late effects in several cell generations after the initial exposure. The thyroid gland is one of the most sensitive organs to the carcinogenic effects of IR, and we have recently highlighted that an oxidative stress is responsible for the chromosomal rearrangements found in radio-induced papillary thyroid carcinoma. Using both a human thyroid cell line and primary thyrocytes, we investigated the mechanism by which IR induces the generation of reactive oxygen species (ROS) several days after irradiation. We focused on NADPH oxidases, which are specialized ROS-generating enzymes known as NOX/DUOX. Our results show that IR induces delayed NADPH oxidase DUOX1-dependent H2O2 production in a dose-dependent manner, which is sustained for several days. We report that p38 MAPK, activated after IR, increased DUOX1 via IL-13 expression, leading to persistent DNA damage and growth arrest. Pretreatment of cells with catalase, a scavenger of H2O2, or DUOX1 down-regulation by siRNA abrogated IR-induced DNA damage. Analysis of human thyroid tissues showed that DUOX1 is elevated not only in human radio-induced thyroid tumors, but also in sporadic thyroid tumors. Taken together, our data reveal a key role of DUOX1-dependent H2O2 production in long-term persistent radio-induced DNA damage. Our data also show that DUOX1-dependent H2O2 production, which induces DNA double-strand breaks, can cause genomic instability and promote the generation of neoplastic cells through its mutagenic effect.

Dose reduction in orthodontic lateral cephalography: dosimetric evaluation of a novel cephalographic thyroid protector (CTP) and anatomical cranial collimation (ACC)

OBJECTIVES

To test the dose-reducing capabilities of a novel thyroid protection device and a recently introduced cranial collimator to be used in orthodontic lateral cephalography.

METHODS

Cephalographic thyroid protector (CTP) was designed to shield the thyroid while leaving the cervical vertebrae depicted. Using a RANDO(®) head phantom (The Phantom Laboratory, Salem, NY) equipped with dosemeters and a Proline XC (Planmeca, Helsinki, Finland) cephalograph, lateral cephalograms were taken, and the effective dose (ED) was calculated for four protocols: (1) without shielding; (2) with CTP; (3) with CTP and anatomical cranial collimator (ACC); and (4) with a thyroid collar (TC).

RESULTS

The ED for the respective protocols was (1) 8.51; (2) 5.39; (3) 3.50; and (4) 4.97 µSv. The organ dose for the thyroid was reduced from 30.17 to 4.50 µSv in Protocols 2 and 3 and to 3.33 µSv in Protocol 4.

CONCLUSIONS

The use of just the CTP (Protocol 2) resulted in a 36.8% reduction of the ED of a lateral cephalogram. This was comparable to the classical TC (Protocol 4). A 58.8% reduction of the ED was obtained when combining CTP and ACC (Protocol 3). The dose to the radiosensitive thyroid gland was reduced by 85% in Protocols 2 and 3 and by 89% in Protocol 4.

Menstrual and reproductive factors in the risk of differentiated thyroid carcinoma in young women in France: a population-based case-control study

The incidence of thyroid cancer has increased in eastern Europe since the Chernobyl nuclear power plant accident. Although the radioactive fallout was much less severe and the thyroid radiation dose was much lower in France, a case-control study was initiated in eastern France. The present study included 633 young women who were diagnosed with differentiated thyroid cancer before 35 years of age between 2002 and 2006 and matched with 677 controls. Face-to-face interviews were conducted from 2005 to 2010. Odds ratios were calculated using conditional logistic regressions and were reported in the total group and by histopathological type of cancer ("only papillary" and "excluding microcarcinomas"). The risk of thyroid cancer was higher in women who had a higher number of pregnancies, used a lactation suppressant, or had early menarche. Conversely, breastfeeding, oral contraceptive use, and late age at first pregnancy were associated with a lower risk of thyroid cancer. No association was observed between thyroid cancer and having irregular menstrual cycle, undergoing treatment for menstrual cycle regularity shortly after menarche, having a cessation of menstruation, use of another contraceptive, history of miscarriage or abortion for the first pregnancy, or having had gestational diabetes. This study confirms the role of hormonal and reproductive factors in thyroid cancer, and our results support the fact that exposure to estrogens increases thyroid cancer risk.

Controversy over radioiodine ablation in thyroid cancer: who benefits?

Recent studies have proposed that overdiagnosis is probably the principal cause of the increased incidence of thyroid cancer. The controversy around radioiodine ablation is complicated by the ever increasing numbers of small, low-risk thyroid cancers being diagnosed. This article examines the history and evolving epidemiology of the disease and treatment.

Thyroid cancer incidence in the vicinity of nuclear sites in Belgium, 2000-2008

BACKGROUND

Public health concern about nuclear activities have existed since the 1980s. Most studies on this subject investigated childhood leukemia. Thyroid cancer may be another health outcome of interest, because some nuclear installations are a potential source of radioactive iodine isotopes in the environment and because thyroid cancer is known to occur after exposure to these isotopes.

METHODS

This study describes an ecological study investigating whether there is excessive thyroid cancer incidence among residents living in the vicinity of nuclear sites. Single-site analyses using indirect standardization (standardized incidence ratios [SIRs]) and Poisson regression modeling (rate ratios [RRs]) were conducted. The proximity area is typically defined as a circular zone with a radius of 20 km centered on the site. However, the choice of the size of this area is somewhat arbitrary. Therefore, a sensitivity analysis was carried out to investigate whether the results vary with radii of increasing proximity.

RESULTS

No increased thyroid cancer incidence was found within the 20 km proximity area around the nuclear power plants of Doel (SIR=0.74 [95% confidence interval (CI)=0.64; 0.84] and RR=0.72 [95% CI=0.63; 0.83]) and Tihange (SIR=0.86 [95% CI=0.70; 1.01] and RR=0.85 [95% CI=0.70; 1.02]). For the sites of Mol-Dessel and Fleurus, where a combination of nuclear research and industrial activities are located, the incidences of thyroid cancer within the 20 km proximity area were higher than expected (Mol-Dessel: SIR=1.19 [95% CI=1.01; 1.36] and RR=1.19 [95% CI=1.02; 1.38]; Fleurus: SIR=1.15 [95% CI=1.02; 1.28] and RR=1.17 [95% CI=1.04; 1.33]). For Chooz, a French nuclear power plant close to the Belgian border, the results were unstable as a result of the small population denominator. For all Belgian nuclear sites, the results were generally insensitive to the choice of the proximity area.

CONCLUSIONS

No evidence for excessive thyroid cancer incidence around the Belgian nuclear power plants was found. On the other hand, an increased incidence of thyroid cancer was observed around the sites with other nuclear activities. Further research is recommended to verify whether the observed increases could be related to the site-specific nuclear activities.

Hyperparathyroidism two years after radioactive iodine therapy in an adolescent male

Primary hyperparathyroidism is a very rare complication following radioactive iodine therapy. There is typically a latency period of more than a decade following radiation exposure and, therefore, it is observed almost exclusively in adults. Consequently, pediatricians are not aware of the association. We present a case of primary hyperparathyroidism due to a solitary parathyroid adenoma occurring in an adolescent male two years following radioactive iodine treatment for papillary thyroid carcinoma. Periodic screening of serum calcium following ablative doses of radioactive iodine for thyroid cancer may be justified even in adolescents.

Recent Trends and Geographical Distribution of Thyroid Cancer in Iran from 2004 to 2009

BACKGROUND

To prevent and control the cancers in Iran, the Iranian Department of Health has released the cancer rates data of the country. As the report has suggested, the incidence rate of thyroid cancer would be the most rapidly increasing among all the cancers. The study has aimed to carry out a qualitative assessment of thyroid cancer in Iran, during the 2004 to 2009, in a cross-sectional setting.

METHODS

The incidence rates, the trend of individual provinces, the mean age at which the disease occurred, the correlation between incidence rate and median urinary iodine concentration were the parameters evaluated in our study.

RESULTS

The average annual incidence rate during these six years was 2.17 per 100000. Chaharmahal-o-bakhtiari, had the highest incidence rate, but the East Azerbaijan provinces had the lowest incidence rates respectively. The age of diagnosis was the lowest in Ardebil but the highest in West Azerbaijan. In our study, we have found the positive correlation between thyroid cancer incidences with low urinary iodine concentration among all provinces (p-value=0.025).

CONCLUSION

Presently, the only recognized measure procedure for reducing thyroid cancer risk would be perhaps the correction of median urinary iodine concentration. Further researches have seemed to be required for investigation the other factors, in order to introduce preventive measures in Iran.

Association of ATM Gene Polymorphism with PTC Metastasis in Female Patients

Ataxia telangiectasia mutated (ATM) gene is critical in the process of recognizing and repairing DNA lesions and is related to invasion and metastasis of malignancy. The incidence rate of papillary thyroid cancer (PTC) has increased for several decades and is higher in females than males. In this study, we want to investigate whether ATM polymorphisms are associated with gender-specific metastasis of PTC. 358 PTC patients in Northern China, including 109 males and 249 females, were included in our study. Four ATM single nucleotide polymorphisms (SNPs) were genotyped using Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF-MS). Association between genotypes and the gender-specific risk of metastasis was assessed by odds ratios (OR) and 95% confidence intervals (CI) under the unconditional logistic regression analysis. Significant associations were observed between rs189037 and metastasis of PTC in females under different models of inheritance (codominant model: OR = 0.15, 95% CI 0.04-0.56, P = 0.01 for GA versus GG and OR = 0.08, 95% CI 0.01-0.74, P = 0.03 for AA versus GG, resp.; dominant model: OR = 0.49, 95% CI 0.25-0.98, P = 0.04; overdominant model: OR = 0.47, 95% CI 0.25-0.89, P = 0.02). However, no association remained significant after Bonferroni correction. Our findings suggest a possible association between ATM rs189037 polymorphisms and metastasis in female PTCs.

Genetic alterations in thyroid tumors from patients irradiated in childhood for tinea capitis treatment

OBJECTIVE

Exposure to ionizing radiation at young age is the strongest risk factor for the occurrence of papillary thyroid carcinoma (PTC). RET/PTC rearrangements are the most frequent genetic alterations associated with radiation-induced PTC, whereas BRAF and RAS mutations and PAX8-PPARG rearrangement have been associated with sporadic PTC. We decided to search for such genetic alterations in PTCs of patients subjected in childhood to scalp irradiation.

DESIGN

We studied 67 thyroid tumors from 49 individuals irradiated in childhood for tinea capitis scalp epilation: 36 malignant (12 cases of conventional PTC (cPTC), two cPTC metastases, 20 cases of follicular variant PTC (FVPTC), one oncocytic variant of PTC and one follicular carcinoma) and 31 follicular thyroid adenomas.

METHODS

The lesions were screened for the BRAF(V600E) and NRAS mutations and for RET/PTC and PAX8-PPARG rearrangements.

RESULTS

BRAF(V600E) mutation was detected in seven of 14 (50%) cPTC and two of 20 FVPTC (10%) (P=0.019). NRAS mutation was present in one case of FVPTC (5%). RET/PTC1 rearrangement was found, by RT-PCR, in one of 17 cases (5.9%) and by fluorescence in situ hybridization in two of six cases (33%). PAX8-PPARG rearrangement was not detected in any carcinoma. None of the follicular adenomas presented any of the aforementioned genetic alterations.

CONCLUSIONS

The prevalence of BRAF(V600E) mutation in our series is the highest reported in series of PTCs arising in radiation-exposed individuals. The prevalence of RET/PTC1 rearrangement fits with the values recently described in a similar setting.

The increasing incidence of thyroid cancer: the influence of access to care

BACKGROUND

The rapidly rising incidence of papillary thyroid cancer may be due to overdiagnosis of a reservoir of subclinical disease. To conclude that overdiagnosis is occurring, evidence for an association between access to health care and the incidence of cancer is necessary.

METHODS

We used Surveillance, Epidemiology, and End Results (SEER) data to examine U.S. papillary thyroid cancer incidence trends in Medicare-age and non-Medicare-age cohorts over three decades. We performed an ecologic analysis across 497 U.S. counties, examining the association of nine county-level socioeconomic markers of health care access and the incidence of papillary thyroid cancer.

RESULTS

Papillary thyroid cancer incidence is rising most rapidly in Americans over age 65 years (annual percentage change, 8.8%), who have broad health insurance coverage through Medicare. Among those under 65, in whom health insurance coverage is not universal, the rate of increase has been slower (annual percentage change, 6.4%). Over three decades, the mortality rate from thyroid cancer has not changed. Across U.S. counties, incidence ranged widely, from 0 to 29.7 per 100,000. County papillary thyroid cancer incidence was significantly correlated with all nine sociodemographic markers of health care access: it was positively correlated with rates of college education, white-collar employment, and family income; and negatively correlated with the percentage of residents who were uninsured, in poverty, unemployed, of nonwhite ethnicity, non-English speaking, and lacking high school education.

CONCLUSION

Markers for higher levels of health care access, both sociodemographic and age-based, are associated with higher papillary thyroid cancer incidence rates. More papillary thyroid cancers are diagnosed among populations with wider access to healthcare. Despite the threefold increase in incidence over three decades, the mortality rate remains unchanged. Together with the large subclinical reservoir of occult papillary thyroid cancers, these data provide supportive evidence for the widespread overdiagnosis of this entity.

A prospective study of medical diagnostic radiography and risk of thyroid cancer

Although diagnostic x-ray procedures provide important medical benefits, cancer risks associated with their exposure are also possible, but not well characterized. The US Radiologic Technologists Study (1983-2006) is a nationwide, prospective cohort study with extensive questionnaire data on history of personal diagnostic imaging procedures collected prior to cancer diagnosis. We used Cox proportional hazard regressions to estimate thyroid cancer risks related to the number and type of selected procedures. We assessed potential modifying effects of age and calendar year of the first x-ray procedure in each category of procedures. Incident thyroid cancers (n = 251) were diagnosed among 75,494 technologists (1.3 million person-years; mean follow-up = 17 years). Overall, there was no clear evidence of thyroid cancer risk associated with diagnostic x-rays except for dental x-rays. We observed a 13% increase in thyroid cancer risk for every 10 reported dental radiographs (hazard ratio = 1.13, 95% confidence interval: 1.01, 1.26), which was driven by dental x-rays first received before 1970, but we found no evidence that the relationship between dental x-rays and thyroid cancer was associated with childhood or adolescent exposures as would have been anticipated. The lack of association of thyroid cancer with x-ray procedures that expose the thyroid to higher radiation doses than do dental x-rays underscores the need to conduct a detailed radiation exposure assessment to enable quantitative evaluation of risk.

Common single nucleotide polymorphisms in genes related to immune function and risk of papillary thyroid cancer

Accumulating evidence suggests that alterations in immune function may be important in the etiology of papillary thyroid cancer (PTC). To identify genetic markers in immune-related pathways, we evaluated 3,985 tag single nucleotide polymorphisms (SNPs) in 230 candidate gene regions (adhesion-extravasation-migration, arachidonic acid metabolism/eicosanoid signaling, complement and coagulation cascade, cytokine signaling, innate pathogen detection and antimicrobials, leukocyte signaling, TNF/NF-kB pathway or other) in a case-control study of 344 PTC cases and 452 controls. We used logistic regression models to estimate odds ratios (OR) and calculate one degree of freedom P values of linear trend (P(SNP-trend) ) for the association between genotype (common homozygous, heterozygous, variant homozygous) and risk of PTC. To correct for multiple comparisons, we applied the false discovery rate method (FDR). Gene region- and pathway-level associations (P(Region) and P(Pathway)) were assessed by combining individual P(SNP-trend) values using the adaptive rank truncated product method. Two SNPs (rs6115, rs6112) in the SERPINA5 gene were significantly associated with risk of PTC (P(SNP-FDR)/P(SNP-trend)= 0.02/6×10(-6) and P(SNP-FDR)/P(SNP-trend)= 0.04/2×10(-5), respectively). These associations were independent of a history of autoimmune thyroiditis (OR = 6.4; 95% confidence interval: 3.0-13.4). At the gene region level, SERPINA5 was suggestively associated with risk of PTC (P(Region-FDR)/P(Region)= 0.07/0.0003). Overall, the complement and coagulation cascade pathway was the most significant pathway (P(Pathway)= 0.02) associated with PTC risk largely due to the strong effect of SERPINA5. Our results require replication but suggest that the SERPINA5 gene, which codes for the protein C inhibitor involved in many biological processes including inflammation, may be a new susceptibility locus for PTC.

Protection against radiation-induced damage of 6-propyl-2-thiouracil (PTU) in thyroid cells

Many epidemiologic studies have shown that the exposure to high external radiation doses increases thyroid neoplastic frequency, especially when given during childhood or adolescence. The use of radioprotective drugs may decrease the damage caused by radiation therapy and therefore could be useful to prevent the development of thyroid tumors. The aim of this study was to investigate the possible application of 6-propyl-2-thiouracil (PTU) as a radioprotector in the thyroid gland. Rat thyroid epithelial cells (FRTL-5) were exposed to different doses of γ irradiation with or without the addition of PTU, methimazole (MMI), reduced glutathione (GSH) and perchlorate (KClO4). Radiation response was analyzed by clonogenic survival assay. Cyclic AMP (cAMP) levels were measured by radioimmunoassay (RIA). Apoptosis was quantified by nuclear cell morphology and caspase 3 activity assays. Intracellular reactive oxygen species (ROS) levels were measured using the fluorescent dye 2',7'-dichlorofluorescein-diacetate. Catalase, superoxide dismutase and glutathione peroxidase activities were also determined. Pretreatment with PTU, MMI and GSH prior to irradiation significantly increased the surviving cell fraction (SF) at 2 Gy (P < 0.05), while no effect was observed with KClO4. An increase in extracellular levels of cAMP was found only in PTU treated cells in a dose and time-dependent manner. Cells incubated with agents that stimulate cAMP (forskolin and dibutyril cAMP) mimicked the effect of PTU on SF. Moreover, pretreatment with the inhibitor of protein kinase A, H-89, abolished the radioprotective effect of PTU. PTU treatment diminished radiation-induced apoptosis and protected cells against radiation-induced ROS elevation and suppression of the antioxidant enzyme's activity. PTU was found to radioprotect normal thyroid cells through cAMP elevation and reduction in both apoptosis and radiation-induced oxidative stress damage.

[Differentiated thyroid cancer in childhood]

Thyroid carcinoma is a rare disease in children, and is mostly of the papillary histological type. Lymph node metastases are frequent at diagnosis, being present in 23 to 74% of the cases and can reveal the cancer in about one fourth of cases. Lung metastases are present at initial diagnosis in 6 to 20% of cases. The main known risk factor for thyroid cancer is a previous history of radiation exposure. Treatment includes surgery with total thyroidectomy and lymph node dissection and radioiodine therapy in case of extensive disease and distant metastases. Life-long thyroxine treatment is given to all patients. Long term prognosis is favourable, but thyroid cancer related deaths have been reported some decades after initial treatment.

No thyroid abnormalities in patients submitted to cardiac catheterization in the first eighteen months of life

BACKGROUND

No data are available about the risk of thyroid disturbance after exposure to low-dose radiation due to the use of cardiac catheterization in the first years of life.

AIM

To determine the risk of functional and morphological thyroid abnormalities in a homogeneous cohort of patients who underwent diagnostic low-dose radiation for heart catheterization during the first 18 months of life.

SUBJECTS AND METHODS

Fifty-five patients, submitted to cardiac catheterization during the first 18 months of life, underwent evaluation of the thyroid function and structure after a median period of 13 yr since the first radiation exposure. Sixty-eight unexposed controls matched for age and sex, underwent the same protocol. Twenty-two patients were then re-evaluated after a median period of 22 yr.

RESULTS

Thyroid function resulted normal in both patients and controls. The prevalence of small thyroid nodules and inhomogeneous structures in ultrasound study was not augmented in irradiated patients compared to controls. No thyroid tumors or reduced thyroid volume were observed.

CONCLUSIONS

Neither functional nor morphological disorders of the thyroid gland were demonstrated after a period up to 24 yr in patients exposed to diagnostic ionizing radiation for cardiac catheterization during the first 18 months of life.

Modifications in the papillary thyroid cancer gene profile over the last 15 years

BACKGROUND

Evidence for an increased prevalence of BRAF(V600E) mutations has been documented in recent decades. The aim of this study was to evaluate the prevalence of both RET/PTC rearrangements and BRAF(V600E) mutations in an Italian cohort of papillary thyroid carcinoma (PTC) patients followed at the Endocrine Units of Pisa, Milano, and Perugia from 1996-2010.

PATIENTS AND METHODS

In total, 401 PTC patients were examined and grouped according to the time of surgery: group 1, 1996-2000; group 2, 2001-2005; and group 3, 2006-2010. Patients were analyzed for clinical, pathological, and molecular features. In parallel, the molecular characteristics of 459 PTC from Sicily were studied.

RESULTS

The genetic profiles of the three groups were significantly different (P < 0.0001). In particular, the frequency of RET/PTC rearrangements decreased from 1996-2010, occurring in 33 of 100 (33%) of the patients in group 1, 26 of 148 (17%) in group 2, and 15 of 153 (9.8%) in group 3. The incidence of BRAF(V600E) mutations increased over the same period, from 28% in group 1 (28 of 100) to 48.9% in group 2 (73 of 148) and 58.1% in group 3 (89 of 153). A consistent increase in BRAF(V600E) prevalence was observed in the Sicilian group (P < 0.0001). Moreover, a statistically significant increase in the mean age at diagnosis and decrease in tumor size over the study period was observed.

CONCLUSION

The genetic profile of PTC changed over the last 15 yr, with a significant decrease in the prevalence of RET/PTC rearrangements and an increase in BRAF(V600E) mutations. In addition, the mean age at diagnosis increased and tumor size decreased over the study period.

[Nuclear-power-plant accidents: thyroid cancer incidence and radiation-related health effects from the Chernobyl accident]

Following the Chernobyl accident, enormous amounts of radioisotopes were released in the atmosphere and have contaminated surrounding populations in the absence of rapid protective countermeasures. The highest radiation doses were delivered to the thyroid gland, and the only direct consequence of radiation exposure observed among contaminated population is the increased incidence of thyroid cancers among subjects who were children in 1986 and who lived at that time in Belarus, Ukraine or Russia.

Increasing incidence of thyroid cancer in Great Britain, 1976-2005: age-period-cohort analysis

Increases in the incidence of thyroid cancer have been previously reported. The purpose of the present study was to examine temporal trends in the incidence of primary thyroid cancer diagnosed in 0-49 year olds in parts of Great Britain during 1976-2005. Data on 4,337 cases of thyroid cancer were obtained from regional cancer registries. Age-standardized incidence rates (ASRs) were calculated. Negative binomial regression was used to examine effects of age, sex, drift (linear trend), non-linear period and non-linear cohort. The best fitting negative binomial regression model included age (P < 0.001), sex (P < 0.001) and drift (P < 0.001). Non-linear period (P = 0.648) and non-linear cohort (P = 0.788) were not statistically significant. For males aged 0-14, the ASR increased from 0.2 per million persons per year in 1976-1986 to 0.6 in 1997-2005. For males aged 15-29 and 30-49 the ASRs increased from 1.9 to 3.3 and from 7.4 to 12.7, respectively. For females aged 0-14, the corresponding ASR increased from 0.3 to 0.5. For females aged 15-29 and 30-49 the ASRs increased from 6.9 to 12.4 and from 21.2 to 42.3, respectively. For all age groups, there has been a linear increase in incidence of thyroid cancer, which has led to a doubling of the number of cases diagnosed over a twenty year span. The reasons for this increase are not well understood, but it is consistent with findings from other countries.

Changes in the incidence of thyroid cancer between 1991 and 2005 in Italy: a geographical analysis

BACKGROUND

The incidence of thyroid cancer (TC) has been increasing over the last 30 years in several countries, with some of the worldwide highest TC incidence rates (IRs) reported in Italy. The objectives of this study were to evaluate by histological subtypes the geographical heterogeneity of the incidence of TC in Italy and to analyze recent time trends for papillary thyroid carcinoma (PTC) in different cancer registries (CRs).

METHODS

The study included cases of TC (<85 years of age) reported to 25 Italian CRs between 1991 and 2005. Age-standardized IRs were computed for all histological subtypes of TC according to CRs. Estimated annual percent change and joinpoint regression analysis were used for analysis of PTC.

RESULTS

In women, IRs of PTC ranged between 3.5/100,000 in Latina and 8.5/100,000 in Sassari for the period 1991-1995 (a 2.4-fold difference) and between 7.3/100,000 in Alto Adige and 37.5/100,000 in Ferrara for 2001-2005 (a 5.1-fold difference). In men, IRs ranged between 0.7/100,000 in Latina and 3.4/100,000 in Sassari for the period 1991-1995 (a 4.9-fold difference) and between 2.0/100,000 (Alto Adige, Trento) and 10.6/100,000 in Ferrara for 2001-2005 (a 5.3-fold difference). In both sexes, IRs significantly higher than the pooled estimates emerged for the most recent period in the majority of CRs located within the Po River plain and in Latina, but they were lower in the Alpine belt. For women, CRs reported higher IRs than pool estimates showed, between 1991 to 2005, a significantly more marked annual percent change (+12%) than other CRs (+7%). For men the corresponding estimates were +11% and +8%.

CONCLUSIONS

The distribution of PTC does not lend support to a role of environmental radiation exposure due to the Chernobyl fallout, iodine deficiency, or (volcanic) soils. Between 1991 and 2005, wide geographic variations in the incidence of PTC and heterogeneous upward trends emerged, suggesting that the heterogeneity was a relatively recent phenomenon; this appeared to be mainly explained by variations, at a local level, in medical surveillance.

The role of FOXO3 in DNA damage response in thyrocytes

Members of the forkhead box-O (FOXO) transcription factors family play an important role in stress defence. FOXO3 deregulation has recently been identified as a hallmark of thyroid carcinogenesis. In this study, we explore the role of FOXO3 in defence of oxidative stress in normal thyrocytes. Stable rat thyroid cell lines were generated expressing either the human wild-type FOXO3, a constitutively activating FOXO3 mutant, or the empty control vector. Cell clones were characterised for proliferation, function and morphology. Hydrogen peroxide and UV irradiation were used to induce oxidative stress. Changes in FOXO3 activity, induction of cell cycle arrest or apoptosis and kinetics of DNA damage repair were analysed. Upregulation of FOXO3 in thyrocytes resulted in decreased proliferation and changes in morphology, but did not affect differentiation. Hydrogen peroxide stimulated the expression of the FOXO3 target genes growth arrest and DNA damage-inducible protein 45 α (Gadd45α) and Bcl-2 interacting mediator of cell death (BIM) and induced programmed cell death in cells with overexpression of the human wild-type FOXO3. In contrast, UV irradiation resulted in a distinct cellular response with activation of FOXO3-c-Jun-N-terminal kinase-Gadd45α signalling and induction of cell cycle arrest at the G(2)-M-checkpoint. This was accompanied by FOXO3-induced DNA damage repair as evidenced by lower DNA breaks over time in a comet assay in FOXO3 cell clones compared with control cells. In conclusion, FOXO3 is a pivotal relay in the coordination of the cellular response to genotoxic stress in the thyroid. Depending on the stimulus, FOXO3 induces either cell cycle arrest or apoptosis. Conversely, FOXO3 inactivation in thyroid cancers is consistent with genomic instability and loss of cell cycle control.

Medical exposure to radiation and thyroid cancer

In 2008, the worldwide estimated age-standardised incidence rates for thyroid cancer incidence were 4.7 and 1.5 per 100,000 women and men, respectively. Thyroid cancer's overall contribution to the worldwide cancer burden is relatively small, but incidence rates have increased over the last three decades throughout the world. This trend has been hypothesised to reflect a combination of technological advances enabling increased detection, but also changes in environmental factors, including population exposure to ionising radiation from fallout, diagnostic tests and treatment for benign and malignant conditions. Studies of the atomic bomb survivors and populations treated with radiotherapy have established radiation as a risk factor for thyroid cancer, particularly from early life exposure. About 0.62 mSv (20%) of the global annual per caput effective radiation dose comes from diagnostic medical and dental radiation for the period of 1997-2007, increased from 0.4 mSv for the years 1991-1996. This international trend of increasing population exposure to medical diagnostic sources of radiation, attributed in large part to the growing use of computed tomography scans, but also interventional radiology procedures, has raised concerns about exposure to radiosensitive organs such as the thyroid. Worldwide, medical and dental X-rays constitute the most common type of diagnostic medical exposures, but their contribution to the cumulative effective dose is relatively low, whereas computed tomography scans account for 7.9% of diagnostic radiology examinations but 47% of the collective effective dose from diagnostic radiation procedures in parts of the world. Although the radiation exposure from computed tomography scans is substantially lower than that from radiotherapy, multiple computed tomography scans could result in non-trivial cumulative doses to the thyroid. Studies are currently underway to assess the incidence of cancer in large cohorts of children who received computed tomography scans. National and international efforts have been developed to raise awareness and to standardise procedures for use of computed tomography and interventional radiology procedures in paediatric and general populations.