Multistage carcinogenesis and the incidence of thyroid cancer in the US by sex, race, stage and histology

Fyn and Lyn gene polymorphisms impact the risk of thyroid cancer

Thyroid cancer is the most common malignancy of the endocrine glands, and during last couple of decades, its incidence has risen alarmingly, across the globe. Etiology of thyroid cancer is still debatable. There are a few worth mentioning risk factors which contribute to initiation of abnormalities in thyroid gland leading to cancer. Genetic instability is major risk factors in thyroid carcinogenesis. Among the genetic factors, the Src family of genes (Src, Yes1, Fyn and Lyn) have been implicated in many cancers but there is little data regarding the association of these (Src, Yes1, Fyn and Lyn) genes with thyroid carcinogenesis. Fyn and Lyn genes of Src family found engaged in proliferation, migration, invasion, angiogenesis, and metastasis in different cancers. This study was planned to examine the effect of Fyn and Lyn SNPs on thyroid cancer risk in Pakistani population in 500 patients and 500 controls. Three polymorphisms of Fyn gene (rs6916861, rs2182644 and rs12910) and three polymorphisms of Lyn gene (rs2668011, rs45587541 and rs45489500) were analyzed using Tetra-primer ARMS-PCR followed by DNA sequencing. SNP rs6916861 of Fyn gene mutant genotype (CC) showed statistically significant threefold increased risk of thyroid cancer (P < 0.0001). In case of rs2182644 of Fyn gene, mutant genotype (AA) indicated statistically significant 17-fold increased risk of thyroid cancer (P < 0.0001). Statistically significant threefold increased risk of thyroid cancer was observed in genotype AC (P < 0.0001) of Fyn gene polymorphism rs12910. In SNP rs2668011 of Lyn gene, TT genotype showed statistically significant threefold increased risk of thyroid cancer (P < 0.0001). In case of rs45587541 of Lyn gene, GA genotypes showed statistically significant 11-fold increased risk in thyroid cancer (P < 0.0001). Haplotype analysis revealed that AAATAG*, AGACAG*, AGCCAA*, AGCCAG*, CAATAG*, CGCCAG* and CGCCGA* haplotypes of Fyn and Lyn polymorphisms are associated with increased thyroid cancer risk. These results showed that genotypes and allele distribution of Fyn and Lyn are significantly linked with increased thyroid cancer risk and could be genetic adjuster for said disease.

Modeling age-specific incidence of colon cancer via niche competition

Cancer development is a multistep process often starting with a single cell in which a number of epigenetic and genetic alterations have accumulated thus transforming it into a tumor cell. The progeny of such a single benign tumor cell expands in the tissue and can at some point progress to malignant tumor cells until a detectable tumor is formed. The dynamics from the early phase of a single cell to a detectable tumor with billions of tumor cells are complex and still not fully resolved, not even for the well-known prototype of multistage carcinogenesis, the adenoma-adenocarcinoma sequence of colorectal cancer. Mathematical models of such carcinogenesis are frequently tested and calibrated based on reported age-specific incidence rates of cancer, but they usually require calibration of four or more parameters due to the wide range of processes these models aim to reflect. We present a cell-based model, which focuses on the competition between wild-type and tumor cells in colonic crypts, with which we are able reproduce epidemiological incidence rates of colon cancer. Additionally, the fraction of cancerous tumors with precancerous lesions predicted by the model agree with clinical estimates. The correspondence between model and reported data suggests that the fate of tumor development is majorly determined by the early phase of tumor growth and progression long before a tumor becomes detectable. Due to the focus on the early phase of tumor development, the model has only a single fit parameter, the time scale set by an effective replacement rate of stem cells in the crypt. We find this effective rate to be considerable smaller than the actual replacement rate, which implies that the time scale is limited by the processes succeeding clonal conversion of crypts.

Cancer development is a multistep process often starting with a single cell turning into a tumor cell whose progeny growths via clonal expansion into a macroscopic tumor with billions of cells. While experimental insight exists on the cellular scale and cancer registries provide statistics on detectable tumors, the complex dynamics leading from the microscopic cellular scale to a macroscopic tumor is still not fully resolved. Models of cancer biology are commonly used to explain incidence rates but usually require the fit of several biological parameters due to the complexity of the incorporated processes. We employ a cell-based model based on the competition in colonic crypts, to reproduce epidemiological age-specific incidence rates of colon cancer. Due to the focus on the early stage of tumor development, only the time scale in the model has to be calibrated. The agreement between theoretical prediction and epidemiological observation suggests that the fate of tumor development is dominated by the early phase of tumor development long before a tumor becomes detectable.

A large-scale study of patients with preoperative vocal cord paralysis associated with thyroid disease and related clinicopathological features

BACKGROUND

The performance of thyroidectomies has been increasing over the last decade due to the growing prevalence of thyroid diseases. The purpose of this study was to investigate the clinical significance of preoperative vocal cord paralysis (VCP) associated with thyroid disease and other incidences of malignant or benign lesions, as well as different thyroid pathological features. Additionally, the epidemiological changes of thyroid diseases with preoperative VCP were investigated.

METHODS

Ninety-nine out of 12,530 patients with preoperative VCP who had undergone thyroid surgery for various diseases in the Zhejiang Cancer Hospital from January 2007 to December 2015 were identified. Their clinicopathological data was recorded and case distributions from different years and intraoperative recurrent laryngeal nerve statuses were retrospectively analyzed.

RESULTS

The incidence of preoperative VCP in 2007 was reported to be 1.53% (9/590) and had decreased to 0.53% (12/2,247) by 2015 (P < 0.05). Among the 99 patients with preoperative VCP, 81 had malignancies (81.82%), while 18 (18.18%) had benign thyroid diseases. The incidences of preoperative VCP in malignant and benign diseases were 1.13% (81/7,159) and 0.35% (18/5,371), respectively (P < 0.05). There were only 5 (0.04%, 5/12,530) cases of papillary thyroid microcarcinoma with preoperative VCP. There was no statistical difference between the incidence of preoperative hoarseness in malignant 69.14% (56/81) and benign diseases 61.11% (11/18) with preoperative VCP.

CONCLUSIONS

The preoperative VCP incidence rate had gradually decreased with an increased proportion of papillary thyroid cancer. Preoperative voice symptoms do not necessarily suggest a malignancy. Selective rather than routine preoperative laryngoscopic examinations should be performed on papillary thyroid microcarcinomas. The probability of preoperative VCP in malignancy was significantly higher than in benign lesions.

Thyroid cancer incidence trend and association with obesity, physical activity in the United States

BACKGROUND

State-level racial/ethnic and age differences and the temporal trend of thyroid cancer (TC) incidence in the USA remain unknown. Our research purposes include: Characterizing state-level temporal variation in TC incidence; examining the disparities of TC incidence by state-level race/ethnicity and age; performing an ecological correlation between TC incidence and obesity/physical activity.

METHODS

TC incidence data during 2000-2017 were extracted from the United States cancer statistics. Using joinpoint regression to evaluate TC incidence trends. Annual percent change (APC), average APC (AAPC) and incidence rates were calculated. The obesity prevalence and physical activity level at the state-level were extracted from Behavioral Risk Factor Surveillance System, and the association between state-level AAPC of TC and obesity/physical activity was tested by Pearson correlation coefficient.

RESULTS

We found that the TC incidence had shown an overall downward trend in recent years, but 10 states continued increasing. There were significant differences in state-level race/ethnicity (non-Hispanic Whites as a reference) and age group (45-59 age group as a reference) incidence: Incidence Rate Ratio (IRR) was 0.4-1.2 for non-Hispanic Blacks, 0.7-1.6 for non-Hispanic Asian and Pacific Islanders, 0.4-1.2 for non-Hispanic American Indians/Alaskan Natives, and 0.5-1.3 for Hispanics. High IRR in young people were distributed in northern USA, while in older people were distributed in south. The state-level obesity/physical activity level and AAPC had a weak correlation (r = 0.34, P = 0.016) and inverse weak correlation (r = -0.29, P = 0.037), respectively. The AAPC of states with a consistent increasing trend had an extremely strong correlation with obesity prevalence (r = 0.80, p = 0.006), and an inverse strong correlation with physical activity level (r = -0.65, P = 0.04).

CONCLUSIONS

Thyroid cancer incidence in 10 states continued increasing. State-level variation in race/ethnicity and age group incidence were found. Lifestyle and environmental factors may interfere with the incidence trend of TC in the USA.

Incidence and mortality from thyroid cancer in Latin America

OBJECTIVE

To describe trends in thyroid cancer incidence and mortality in Latin America.

METHODS

Ecological study of time series, with incidence data from the International Agency for Research on Cancer for the 1990-2012 period and mortality data of 16 countries obtained from WHO for the 1995-2013 period. The trends of incidence rates were analysed by the Joinpoint regression. Average annual percentage change and 95% confidence intervals were calculated for incidence and mortality.

RESULTS

Incidence and mortality from thyroid cancer in Latin America were higher in women, with the highest incidence rate in women in Quito (Ecuador) aged 40-59 years: 42.2 new cases per 100 000 inhabitants, and mortality of 4.8/100 000 in women over 60. Thyroid cancer incidence increased in women of all age groups in Cali (Colombia), Costa Rica and Quito (Ecuador); and in men in Costa Rica. Incidence rates were stable above the age of 60 years in Cali, in Goiania (Brazil), Quito (Ecuador) and Valdivia (Chile) in men, and in women in Goiania (Brazil) and Valdivia (Chile). Mortality among women increased in Ecuador (AAPC = 3.28 CI 95% 1.36; 5.24), Guatemala (AAPC = 6.14 CI 95% 2.81; 9.58) and Mexico (AAPC = 0.67 CI 95% 0.16; 1.18).

CONCLUSIONS

Thyroid cancer incidence in Latin America is high and rising in women. Mortality remains stable in most countries of Latin America.

Neck mass and tracheostomy in a young lady depicted by Piero di Cosimo

Among surgical procedures currently in use, tracheostomy has a particularly long history. The first written description of the procedure is due to Brasavola, and dates from 1546. Piero di Cosimo (1462-1522) was an early Renaissance painter who painted a work traditionally known as Cephalus and Procris or The Death of Procris (1495-1500). In this painting, a vertical tracheostomy can be observed in a young woman lying on the ground. A giant mass can be seen in the lower left neck with superficial venous vessels, suggesting a thyroid malignancy. This appears to be the first detailed depiction of a malignant cervical mass and a possibly therapeutic tracheostomy. We discuss the clinical differential diagnosis and also make some comments from an art history perspective.

Case Studies of Gastric, Lung, and Oral Cancer Connect Etiologic Agent Prevalence to Cancer Incidence

Obtaining detailed individual-level data on both exposure and cancer outcomes is challenging, and it is difficult to understand and characterize how temporal aspects of exposures translate into cancer risk. We show that, in lieu of individual-level information, population-level data on cancer incidence and etiologic agent prevalence can be leveraged to investigate cancer mechanisms and to better characterize and predict cancer trends. We use mechanistic carcinogenesis models [multistage clonal expansion (MSCE) models] and data on smoking, Helicobacter pylori (H. pylori), and HPV infection prevalence to investigate trends of lung, gastric, and HPV-related oropharyngeal cancers. MSCE models are based on the initiation-promotion-malignant conversion paradigm and allow for interpretation of trends in terms of general biological mechanisms. We assumed the rates of initiation depend on the prevalence of the corresponding risk factors. We performed two types of analysis, using the agent prevalence and cancer incidence data to estimate the model parameters and using cancer incidence data to infer the etiologic agent prevalence as well as the model parameters. By including risk factor prevalence, MSCE models with as few as three parameters closely reproduced 40 years of age-specific cancer incidence data. We recovered trends of H. pylori prevalence in the United States and demonstrated that cohort effects can explain the observed bimodal, age-specific pattern of oral HPV prevalence in men. Our results demonstrate the potential for joint analyses of population-level cancer and risk factor data through mechanistic modeling. This approach can be a first step in systematically testing relationships between exposures and cancer risk when individual-level data is lacking.Significance: Analysis of trends in risk-factor prevalence and cancer incidence can shed light on cancer mechanisms and the way that carcinogen exposure through time shapes the risk of cancer at different ages.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/12/3386/F1.large.jpg Cancer Res; 78(12); 3386-96. ©2018 AACR.

Thyroid cancer clinical trials in the United States: Understanding trends to maximize impact

BACKGROUND

We sought to understand thyroid cancer study modalities, publications, and grants. This provides scope, resources, and dissemination patterns to inform future directions for research and policy.

METHODS

A retrospective study of thyroid cancer trials using ClinicalTrials.gov was performed. Publication and grant awards were sourced using PubMed.gov and NIH RePORTER, respectively.

RESULTS

Seventy-three thyroid cancer trials were identified out of 217 000 from 1998 to 2015. Drugs were studied in 96% of all trials. Only 14% of all trials included radiation, and 4% included surgery. Only 29% of trials published their results, NIH funding was reported for 26% of trials. Total funding was $1 845 567 484 (average award: $97135131).

CONCLUSION

This study is the first to prove that drug trials predominate in thyroid cancer and quantify NIH dollars awarded. Radiation and surgery are underrepresented, despite being standard of care. We recommend better balance of therapeutics and peer-reviewed reporting of positive and negative results.

LEVEL OF EVIDENCE

Level 1a evidence.

Significant racial differences in the incidence and behavior of the follicular variant of papillary thyroid carcinoma

BACKGROUND

Increased detection of papillary thyroid cancer (PTC) has led to overtreatment of the largely indolent follicular variant (fvPTC). To guide management of non-aggressive lesions, we investigated whether race predicts PTC variant and tumor behavior.

METHODS

Analysis of 258 973 patients from the National Cancer Database diagnosed with PTC in 2004-2014. Clinical and tumor information was compared by race. Multivariate logistic regression was used to predict fvPTC, extrathyroidal extension (ETE), and lymph node metastasis (LNM) of fvPTC.

RESULTS

Blacks had the highest fvPTC rate (40% vs white 30%, Hispanic 26%, Asian 25%, P < .001). Blacks had higher odds of fvPTC (aOR = 1.33, 95% CI: 1.28-1.37) and lower odds of ETE than whites (aOR = 0.90, 95% CI: 0.82-0.99) (P < .001). Hispanics and Asians had lower odds of fvPTC (aOR = 0.89, 95% CI: 0.86-0.92 and aOR = 0.81, 95% CI: 0.79-0.84) and higher odds of LNM and ETE than whites (P < .001).

CONCLUSIONS

Racial disparities in fvPTC incidence and behavior should be considered to optimize diagnosis and treatment planning.

Combined MEK and Pi3'-kinase inhibition reveals synergy in targeting thyroid cancer in vitro and in vivo

Anaplastic thyroid cancers and radioiodine resistant thyroid cancer are posing a major treat since surgery combined with Iodine¹³¹ therapy is ineffective on them. Small-molecule inhibitors are presenting a new hope for patients, but often lead to drug resistance in many cancers. Based on the major mutations found in thyroid cancer, we propose the combination of a MEK inhibitor and a Pi3′-kinase inhibitor in pre-clinical models. We used human thyroid cancer cell lines and genetically engineered double mutant BRAF^V600E PIK3CA^H1047R mice to evaluate the effect of both inhibitors separately or in combination in terms of proliferation and signaling in vitro; tumor burden, histology, cell death induction and tumor markers expression in vivo. The combination of MEK and Pi’3-kinase inhibition shows a synergistic effect in term of proliferation and apoptosis induction through Survivin down-regulation in vitro. We show for the first time the effects of the combination of a MEK inhibitor and Pi3′-kinase inhibitor in a genetically engineered mouse model of aggressively lethal thyroid cancer. In fine, the two drugs cooperate to promote tumor shrinkage by inducing a proliferation arrest and an elevation of apoptosis in vivo. Moreover, a phenotypic reversion is also observed with a partial restoration of normal thyroid marker transcription, and thyroid cancer marker expression reduction.

In conclusion, combination therapy of MEK and Pi3′-kinase inhibition synergizes to target double mutant thyroid cancer in vitro and in vivo. This multidrug approach could readily be translated into clinical practice and bring new perspectives for the treatment of incurable thyroid carcinoma.

Melatonin suppresses thyroid cancer growth and overcomes radioresistance via inhibition of p65 phosphorylation and induction of ROS

Thyroid cancer is the most common endocrine carcinoma with increasing incidence worldwide and anaplastic subtypes are frequently associated with cancer related death. Radioresistance of thyroid cancer often leads to therapy failure and cancer-related death. In this study, we found that melatonin showed potent suppressive roles on NF-κB signaling via inhibition of p65 phosphorylation and generated redox stress in thyroid cancer including the anaplastic subtypes. Our data showed that melatonin significantly decreased cell viability, suppressed cell migration and induced apoptosis in thyroid cancer cell lines in vitro and impaired tumor growth in the subcutaneous mouse model in vivo. By contrast, irradiation of thyroid cancer cells resulted in elevated level of phosphorylated p65, which could be reversed by cotreatment with melatonin. Consequently, melatonin synergized with irradiation to induce cytotoxicity to thyroid cancer, especially in the undifferentiated subgroups. Taken together, our results suggest that melatonin may exert anti-tumor activities against thyroid carcinoma by inhibition of p65 phosphorylation and induction of reactive oxygen species. Radio-sensitization by melatonin may have clinical benefits in thyroid cancer.

Racial/ethnic differences in thyroid cancer incidence in the United States, 2007-2014

BACKGROUND

Small tumor diagnostic tools including ultrasound-guided fine needle aspiration (FNA) and computed tomography (CT) could be causing rising and racially/ethnically different thyroid cancer incidence rates due to variable overdiagnosis of indolent tumors. Papillary tumors and <40 mm tumors are most likely to be overdiagnosed as indolent tumors by FNA and CT.

METHODS

Age-adjusted incidence rates (AAIRs) for the years 2007-2014 were calculated for race/ethnicity (white, Hispanic, Asian, African American, Native American) by patient/tumor characteristics for microscopically confirmed malignant thyroid cancer cases in the Surveillance, Epidemiology, and End Results Program 18 database (SEER 18; N = 93,607). Multivariate analysis determined cancer patients' odds ratios of diagnosis with papillary thyroid carcinoma (vs other histologies) and tumors <40 mm (vs ≥40 mm).

RESULTS

For both males and females, there were statistically significant differences in incidence rates between race/ethnicity, with whites having the highest AAIRs and African Americans the lowest AAIRs. Among thyroid cancer patients, tumor size and histology differed significantly by race and insurance coverage after controlling for age, sex, stage, and tumor sequence. Non-whites with thyroid cancer (vs whites) were less associated with small tumors (odds ratio [OR], 0.51-0.79; P < .0001). Medicaid and uninsured patients with thyroid cancer were less associated with tumors <40 mm (OR, 0.55-0.71; 95% confidence interval [CI], 0.49-0.76) and papillary carcinoma (OR, 0.86; 95% CI, 0.80-0.93).

CONCLUSION

The diagnosis of small tumors is occurring at greater rates in whites (vs non-whites) and insured (vs Medicaid and uninsured) patients; consequently, these groups may be vulnerable to unnecessary tests and treatments or potentially aided by early detection. Guidelines that define postdetection interventions may be needed to limit the overtreatment of indolent and small papillary carcinomas. Cancer 2018;124:1483-91. © 2018 American Cancer Society.

Growing incidence of thyroid carcinoma in recent years: Factors underlying overdiagnosis

There is an increasing incidence of well-differentiated thyroid cancer worldwide. Much of the increase is secondary to increased detection of small, low-risk tumors, with questionable clinical significance. This review addresses the factors that contribute to the increasing incidence and considers environmental, and patient-based and clinician-led influences. Articles addressing the causes of the increased incidence were critically reviewed. A complex interplay of environmental, medical, and social pressures has resulted in increased awareness of the thyroid disease risk, increased screening of thyroid cancers, and increased diagnosis of thyroid cancers. Although there is evidence to suggest that the true disease incidence may be changing slightly, most of the increase is related to factors that promote early diagnosis of low-risk lesions, which is resulting in a significant phenomenon of overdiagnosis. An improved understanding of these pressures at a global level will enable healthcare policymakers to react appropriately to this challenge in the future.

Persistent Elevation of Thyroglobulin in Patient Treated for Differentiated Thyroid Cancer: A Ten-Year Review

Differentiated Thyroid Cancer (DTC) is increasing in prevalence due to better diagnostic tools and excellent long-term survival. This study is to understand the outcome of twenty-six patients with DTC over a period of 10 years after the initial treatment with surgery and radioiodine therapy. Our study analysis showed no deaths, and indicated that older men were more likely to have persistent disease. Further studies are needed to focus on cost effective long-term management of DTC.

Signaling Pathways in Thyroid Cancer

The morbidity of thyroid cancer is increasing gradually year by year, showing an increasing tendency in nationality, sex, age, tumor size, and tumor staging. The changes of thyroid cell genes, signaling pathways, and related molecular dysfunction promote the occurrence, development, invasion, and metastasis of thyroid cancer. Surgical operation, radioiodine, and endocrinotherapy models can achieve a better prognosis for most patients with thyroid cancer. Although targeted therapeutic drugs bring possible therapeutic opportunities for refractory thyroid cancer, there is a great gap between their predictive value and their actual efficacy. Currently, there is still no completely effective drug for the treatment. Based on the signaling pathways, the "reclaim therapy" for residual tumor and systemic intervention aims to increase anticancer ability and to encourage new directions and thoughts in the treatment of refractory thyroid cancer.

Combined MEK and Pi3'-kinase inhibition reveals synergy in targeting thyroid cancer in vitro and in vivo

Anaplastic thyroid cancers and radioiodine resistant thyroid cancer are posing a major treat since surgery combined with Iodine131 therapy is ineffective on them. Small-molecule inhibitors are presenting a new hope for patients, but often lead to drug resistance in many cancers. Based on the major mutations found in thyroid cancer, we propose the combination of a MEK inhibitor and a Pi3'-kinase inhibitor in pre-clinical models. We used human thyroid cancer cell lines and genetically engineered double mutant BRAFV600E PIK3CAH1047R mice to evaluate the effect of both inhibitors separately or in combination in terms of proliferation and signaling in vitro; tumor burden, histology, cell death induction and tumor markers expression in vivo. The combination of MEK and Pi'3-kinase inhibition shows a synergistic effect in term of proliferation and apoptosis induction through Survivin down-regulation in vitro. We show for the first time the effects of the combination of a MEK inhibitor and Pi3'-kinase inhibitor in a genetically engineered mouse model of aggressively lethal thyroid cancer. In fine, the two drugs cooperate to promote tumor shrinkage by inducing a proliferation arrest and an elevation of apoptosis in vivo. Moreover, a phenotypic reversion is also observed with a partial restoration of normal thyroid marker transcription, and thyroid cancer marker expression reduction.In conclusion, combination therapy of MEK and Pi3'-kinase inhibition synergizes to target double mutant thyroid cancer in vitro and in vivo. This multidrug approach could readily be translated into clinical practice and bring new perspectives for the treatment of incurable thyroid carcinoma.

Thyroid-Stimulating Hormone, Thyroid Hormones, and Risk of Papillary Thyroid Cancer: A Nested Case-Control Study

Background: The effects of thyroid-stimulating hormone (TSH) and thyroid hormones on the development of human papillary thyroid cancer (PTC) remain poorly understood.Methods: The study population consisted of 741 (341 women, 400 men) histologically confirmed PTC cases and 741 matched controls with prediagnostic serum samples stored in the Department of Defense Serum Repository. Concentrations of TSH, total T3, total T4, and free T4 were measured in serum samples. Conditional logistic regression models were used to calculate ORs and 95% confidence intervals (CI).Results: The median time between blood draw and PTC diagnosis was 1,454 days. Compared with the middle tertile of TSH levels within the normal range, serum TSH levels below the normal range were associated with an elevated risk of PTC among women (OR, 3.74; 95% CI, 1.53-9.19) but not men. TSH levels above the normal range were associated with an increased risk of PTC among men (OR, 1.96; 95% CI, 1.04-3.66) but not women. The risk of PTC decreased with increasing TSH levels within the normal range among both men and women (P_trend = 0.0005 and 0.041, respectively).Conclusions: We found a significantly increased risk of PTC associated with TSH levels below the normal range among women and with TSH levels above the normal range among men. An inverse association between PTC and TSH levels within the normal range was observed among both men and women.Impact: These results could have significant clinical implications for physicians who are managing patients with abnormal thyroid functions and those with thyroidectomy. Cancer Epidemiol Biomarkers Prev; 26(8); 1209-18. ©2017 AACR.

Integration of a radiation biomarker into modeling of thyroid carcinogenesis and post-Chernobyl risk assessment

Strong evidence for the statistical association between radiation exposure and disease has been produced for thyroid cancer by epidemiological studies after the Chernobyl accident. However, limitations of the epidemiological approach in order to explore health risks especially at low doses of radiation appear obvious. Statistical fluctuations due to small case numbers dominate the uncertainty of risk estimates. Molecular radiation markers have been searched extensively to separate radiation-induced cancer cases from sporadic cases. The overexpression of the CLIP2 gene is the most promising of these markers. It was found in the majority of papillary thyroid cancers (PTCs) from young patients included in the Chernobyl tissue bank. Motivated by the CLIP2 findings we propose a mechanistic model which describes PTC development as a sequence of rate-limiting events in two distinct paths of CLIP2-associated and multistage carcinogenesis. It integrates molecular measurements of the dichotomous CLIP2 marker from 141 patients into the epidemiological risk analysis for about 13 000 subjects from the Ukrainian-American cohort which were exposed below age 19 years and were put under enhanced medical surveillance since 1998. For the first time, a radiation risk has been estimated solely from marker measurements. Cross checking with epidemiological estimates and model validation suggests that CLIP2 is a marker of high precision. CLIP2 leaves an imprint in the epidemiological incidence data which is typical for a driver gene. With the mechanistic model, we explore the impact of radiation on the molecular landscape of PTC. The model constitutes a unique interface between molecular biology and radiation epidemiology.

Iodine deficiency and thyroid cancer trends in three regions of Thailand, 1990-2009

BACKGROUND

Iodine deficiency may play a role in thyroid cancer carcinogenesis. Because Thailand has region-specific historical iodine deficiency, it is ideal to evaluate the potential impact of recent national iodine supplementation policies on thyroid cancer incidence trends.

METHODS

We examined thyroid cancer trends in Thailand from 1990 to 2009 in three geographically separated populations (Songkhla Province [south], Chiang Mai Province [north], and Khon Kaen Province [northeast]), each with a different historical prevalence of iodine deficiency. We used Joinpoint analysis and age-period-cohort (APC) models to investigate trends in thyroid cancer incidence.

RESULTS

Pooled incidence of papillary cancers significantly increased (Males APC: 2.0, p<0.05; Females APC: 7.3 [1990-2001, p<0.05], -2.1 [2001-2009]) and incidence of follicular cancers significantly decreased (Males APC: -5.2, p<0.05; Females APC: -4.3 [1990-1998, p<0.05], 12.3 [1998-2001], -17.0 [2001-2005, p<0.05], 8.2 [2005-2009]) in both males and females between 1990 and 2009. The largest increases in papillary cancer incidence, and the largest decreases in follicular cancer incidence, occurred in historically iodine-deficient regions. Interestingly, the significant histological changes coincided with Thailand's most recent national iodination policy. The thyroid cancer trends in females were better explained by period effects than cohort effects.

CONCLUSIONS

This study adds to the research indicating that papillary carcinoma incidence increases, and follicular carcinoma incidence decreases, as population-level iodine deficiency declines, and suggests that iodine exposure may affect late stages of thyroid carcinogenesis. However, our findings are limited by the ecological study design and lack of data prior to iodine supplementation.