Increasing Gap Between Thyroid Cancer Incidence and Mortality in Urban Shanghai,China: An Analysis Spanning 43 Years

ObjectiveTo examine the secular trends of thyroid cancer incidence and mortality and to estimate the proportion of thyroid cancer cases potentially attributable to overdiagnosis.MethodsData on thyroid cancer cases from 1973 to 2015 were obtained from the Shanghai Cancer Registry. The average annual percent change (AAPC) was evaluated using the joinpoint regression analysis. The age, period, and birth cohort effects were assessed using an age-period-cohort model. The overdiagnosis of thyroid cancer cases was estimated based on the difference between observed and expected incidences using the rates of Nordic countries as reference.ResultsFrom 1973 to 2015, the number of thyroid cancer cases was 23 117, and 75% of the patients were women. The age-standardized rates were seven- to eightfold higher from 2013 to 2015 than from 1973 to 1977. Compared with relatively stable mortality, thyroid cancer incidence was dramatically increased from 2002 to 2015 in both sexes, with significant trends (men: AAPC = 21.84%, 95% CI: 18.77%-24.98%, P < .001; women: AAPC = 18.55%, 95% CI: 16.49%-20.64%, P < .001). The proportion of overdiagnosis has gradually increased over time, rising from 68% between 2003 and 2007 to more than 90% between 2013 and 2015. This increasing trend appeared to be similar between men and women.ConclusionAn increasing gap between thyroid cancer incidence and mortality was observed in Shanghai, and overdiagnosis has contributed substantially to the rise of incidence, which calls for an urgent update on the practice of thyroid examination.     

Temporal and geographical variations of thyroid cancer incidence and mortality in France during 1986–2015: The impact of overdiagnosis

BackgroundFrance is among the countries showing fastest growth of thyroid cancer (TC) incidence and highest incidence rates in Europe. This study aimed to clarify the temporal and geographical variations of TC in France and to quantify the impact of overdiagnosis.MethodsWe obtained TC incidence data in 1986–2015, and mortality data in 1976–2015, for eight French departments covering 8% of the national population, and calculated the age-standardised rates (ASR). We estimated the average annual percent changes (AAPC) of TC incidence, overall and by department and histological subtype. Numbers and proportions of TC cases attributable to overdiagnosis were estimated by department and period, based on the comparison between the shape of the age-specific curves with that observed prior to changes in diagnostic practice.ResultsDuring 1986–2015, there were 13,557 TC cases aged 15–84 years. Large variations of TC incidence were observed across departments, with the highest ASR and the fastest increase in Isère. Papillary subtype accounted for 82.8% of the cases, and presented an AAPC of 7.0% and 7.6% in women and men, respectively. Anaplastic TC incidence decreased annually 3.0% in women and 0.8% in men. Mortality rates declined consistently for all departments. The absolute number (and proportion) of TC cases attributable to overdiagnosis grew from 1074 (66%) in 1986–1995 to 3830 (72%) in 2006–2015 in women, and varied substantially across departments.ConclusionsOverdiagnosis plays an important role in the temporal and regional variations of TC incidence in France. Monitoring the time trends and regulating the regional healthcare practice are needed to reduce its impact.     

Future of cancer incidence in Shanghai,China: Predicting the burden upon the ageing population

AimThe age-specific cancer patterns have changed significantly over the last few decades in urban Shanghai. Predicting the cancer incidence in an ageing population can help to anticipate future resource needs, evaluate primary prevention strategies, and inform further research studies.Materials and MethodsAnnual cancer cases and population data from 1988 to 2013 were collected from Shanghai Cancer Registry. A Bayesian age-period-cohort model was applied to project the future cancer incidence with demographical changes from 2014 to 2025.ResultsFrom 1988 through 2013, the urban population aged < 65 years decreased by 19.5%, while the population aged ≥ 65 years increased by 58.4%. In the same period, cancer cases increased by 66.0% (from 8315 to 13,806) and 88.6% (from 7448 to 14,048) in these two populations, respectively. From 2014–2025, the population size is expected to decrease by an additional 29.6% in people aged < 65 years, while it will increase by an additional 68.3% in people aged ≥ 65 years. Correspondingly, the model predicts an 87.5% and 143.4% increase in cancer cases for these two populations, respectively. The most pronounced increase was found in thyroid cancer in both sexes, followed by prostate, kidney, and colon cancer in men. In women, lung, kidney, and cervical cancer in women was expected to increase.ConclusionsThe number of cancer cases in urban Shanghai, especially in older people, is expected to significantly increase in the next decade. Particular strategies targeting the elderly are required to combat the cancers.     

Ultrasonography survey and thyroid cancer in the Fukushima Prefecture

Thyroid cancer is one of the major health concerns after the accident in the Fukushima Dai-ichi nuclear power station (NPS). Currently, ultrasonography surveys are being performed for persons residing in the Fukushima Prefecture at the time of the accident with an age of up to 18 years. Here, the expected thyroid cancer prevalence in the Fukushima Prefecture is assessed based on an ultrasonography survey of Ukrainians, who were exposed at an age of up to 18 years to ¹³¹I released during the Chernobyl NPS accident, and on differences in equipment and study protocol in the two surveys. Radiation risk of thyroid cancer incidence among survivors of the atomic bombings of Hiroshima and Nagasaki and preliminary estimates of thyroid dose due to the Fukushima accident were used for the prediction of baseline and radiation-related thyroid cancer risks. We estimate a prevalence of thyroid cancer of 0.027 % (95 % CI 0.010 %; 0.050 %) for the first screening campaign in the Fukushima Prefecture. Compared with the incidence rate in Japan in 2007, the ultrasonography survey is predicted to increase baseline thyroid cancer incidence by a factor of 7.4 (95 % CI 0.95; 17.3). Under the condition of continued screening, thyroid cancer during the first fifty years after the accident is predicted to be detected for about 2 % of the screened population. The prediction of radiation-related thyroid cancer in the most exposed fraction (a few ten thousand persons) of the screened population of the Fukushima Prefecture has a large uncertainty with the best estimates of the average risk of 0.1–0.3 %, depending on average dose.     

Increasing incidence and survival of paediatric and adolescent thyroid cancer in Cyprus 1998–2017: A population-based study from the Cyprus Pediatric Oncology Registry

BackgroundPaediatric and adolescent thyroid cancer incidence rates are increasing in many countries. We determined incidence rates, temporal trends and survival from thyroid cancer diagnosed in childhood and adolescence in Cyprus during 1998−2017.MethodsPatients aged 0–19 years, diagnosed with thyroid cancer in the Pediatric Oncology Registry of Cyprus were included. Crude incidence rates, age standardized rates, time trends and overall survival were analysed. Annual rates and temporal trends were calculated using Microsoft Excel 2016 and Joinpoint regression analysis.ResultsEighty-one cases (76.5 % female, 23.5 % male) were identified. The crude rates (per 100,000 persons) were for both sexes 2.00 (95 % CI 1.61, 2.49), females 3.15 (95 % CI 2.45, 4.03) and males 0.92 (95 % CI 0.58, 1.44). The annual percentage changes of crude and standardised rates were 7.5 % (p < 0.05) and 7.6 % (p < 0.05). The annual percentage changes of crude rates were for females 5.1 % (p = 0.1), males 8.4 % (p < 0.05) and 15−19-year-olds 7.6 % (p < 0.05). The female to male rate ratio was 3.42 (95 % CI 2.06, 5.74). Papillary thyroid carcinoma represented 86.4 % of all cases. There was only one case after previous cancer therapy. The rate ratio of 2nd (2008−2017) to 1st (1998−2007) periods for metastatic (regional) stages was 3.76 (95 % CI 1.74, 8.31). Survival until 2018 was 100 %.ConclusionThis population-based study demonstrated that thyroid cancer incidence rates in 0–19-year-olds in Cyprus was among the world’s highest. Increasing trends mainly affected males and females aged 15−19 years with papillary thyroid carcinoma, the dominant type. Cases after previous cancer therapy didn’t contribute to increasing rates. The increase of metastatic cases suggests a true increase of thyroid cancer rather than overdiagnosis. Although prognosis is excellent with 100 % survival, the rising incidence rate is unexplained, indicating the need to identify causes.     

Adolescent and young adult cancers in India–Findings from the National Cancer Registry Programme

BackgroundThe adolescent and young adult (AYA) age group is a bridge between pediatric and adult age groups. The present study describes the epidemiology of cancers in the AYA age group in India.MethodsThe data of primary site cancers in the age group of 15–39 years from the 28 Population Based Cancer Registries (PBCRs') and 58 Hospital Based Cancer Registries under the National Cancer Registry Programme for the reporting year 2012–2016 was analysed.ResultsThe median age adjusted incidence rate (AAR) was 22.2 per 100,000 among males and 29.2 per 100,000 among females. The age-specific incidence rate increased with increasing age in both genders with the highest recorded numbers in the 35–39 age group. The proportion of myeloid leukaemia and non-Hodgkin's lymphoma was highest in the 15–24 age group. Cancers of the breast, thyroid, mouth and tongue constituted the leading sites between 30 and 39 years. There was a significant increase in the incidence among AYA males (APC=0.9) between 1985 and 2015, while a decline in incidence was observed for females, which was not significant (APC=−0.2). The majority of patients had locoregional spread of cancer at the time of diagnosis. The projected number of cancer cases in both genders are expected to increase to 178,617 in 2025.ConclusionCancers in the AYA population are a concern in India. Since AYA oncology appears to be evolving in India, a robust health care system and suitable AYA cancer care policies and programmes are strongly needed to improve disease outcomes and survival.     

Risk of thyroid cancer among Chernobyl emergency workers of Russia

The presented paper deals with the thyroid cancer incidence in selected cohorts of emergency workers of Russia. In 1986-2003, a total of 87 cases of thyroid cancer were observed. Based on these data, a statistically significant increase in thyroid cancer incidence was found above the reference level for the male population of Russia, corresponding to a standardized incidence rate (SIR) of SIR = 3.47 [95% confidence interval (CI): 2.80; 4.25]. The highest incidence rate (SIR = 6.62, 95% CI: 4.63; 9.09) was shown for those emergency workers who took part in the early recovery operations in April-July 1986. The estimated SIR value increases to 7.97 (95% CI: 5.24; 11.52) after allowing for a 10 years latent period of Chernobyl-related thyroid cancers. These results indicate that the exposure to incorporated (131)I was the major risk factor of thyroid cancer among Chernobyl emergency workers. No statistically significant relationship was found for the thyroid cancer incidence and external radiation dose.     

Age-specific calibration for in vivo monitoring of thyroid: is it necessary?

Usually, an age-specific calibration of detectors used for in vivo monitoring of ¹³¹I thyroid radioactivity is not performed in practice. This study aimed to investigate the reduction in uncertainty that one can expect if an age-specific calibration is performed. For this, voxel and stylized computational phantoms of the thyroid, corresponding to children at different age groups, were used to simulate the calibration process of ¹³¹I detectors used for thyroid monitoring. SCK?CEN physical phantoms were also used for this purpose. Both analytical and Monte Carlo methods (MCNPX version 2.6.0) were used to estimate the counting efficiencies of the considered detectors. The results show that the uncertainties in the assessment of thyroid activity at a distance of 20 cm would be reduced from a range of?+8% to?+30%, to a range from ? 6% to?+15% when age-specific calibration was performed. Using a calibration based on thyroids of adults would result in an overestimation of the thyroid activity for children by up to 30% at a detector-neck distance of about 20 cm; a larger overestimation may be expected at closer distances. It is concluded that age-specific calibration of in vivo monitoring systems for the thyroid is important and has to be taken into consideration to improve the reliability of thyroid dose assessment for children.

     

Five-year relative survival and determinants of excess mortality in patients with head and neck and thyroid cancers: A population-based study from Golestan province,Northern Iran

BackgroundWe aimed to assess relative survival (RS) and determinants of excess mortality rate in patients with head and neck squamous cell carcinomas (HNSCC) and thyroid cancer in Golestan province, Northern Iran.MethodsWe recruited new primary HNSCC and thyroid cancer cases from Golestan, 2006–2016. Five-year age-standardized RS with their 95% confidence intervals (CIs) were calculated. The relationships between different variables with excess mortality rates were assessed by estimating adjusted excess hazard ratios (aEHRs) with their 95% CIs.ResultsOverall, 718 cases of HNSCC and 386 thyroid cancer cases were enrolled. Five-year age-standardized RS (95% CI) were 36% (31−41) and 61% (52−69) in HNSCC and thyroid cancer patients, respectively. There were significant relationship between excess mortality rates in HNSCC patients with metastasis (aEHR= 3.31; 95%CI: 2.26–4.84), treatment type (4.19; 2.54–6.91, for no treatment as compared to receiving both surgery and chemoradiotherapy), age (2.16; 1.57–2.96, for older age group) and smoking (2.00; 1.45–2.75, for smokers as compared to non-smokers). Determinant of the excess mortality in thyroid cancer patients included metastasis (19.65; 8.08–47.79), tumor morphology (12.27; 4.62–32.58, for anaplastic cancer as compared to papillary cancer), treatment type (8.95, 4.13–19.4, for no treatment as compared to receiving both surgery and iodine therapy) and age (2.31; 1.17–4.54, for older age group).ConclusionOur findings suggested low RS for thyroid cancer in our population, while the estimates for HNSCC were comparable with other population. Metastasis, treatment type and age were determinants of mortality both in thyroid and HNSCC patients.     

Impact of Uncertainties in Exposure Assessment on Thyroid Cancer Risk among Persons in Belarus Exposed as Children or Adolescents Due to the Chernobyl Accident

BackgroundThe excess incidence of thyroid cancer in Ukraine and Belarus observed a few years after the Chernobyl accident is considered to be largely the result of ¹³¹I released from the reactor. Although the Belarus thyroid cancer prevalence data has been previously analyzed, no account was taken of dose measurement error.MethodsWe examined dose-response patterns in a thyroid screening prevalence cohort of 11,732 persons aged under 18 at the time of the accident, diagnosed during 1996–2004, who had direct thyroid ¹³¹I activity measurement, and were resident in the most radio-actively contaminated regions of Belarus. Three methods of dose-error correction (regression calibration, Monte Carlo maximum likelihood, Bayesian Markov Chain Monte Carlo) were applied.ResultsThere was a statistically significant (p<0.001) increasing dose-response for prevalent thyroid cancer, irrespective of regression-adjustment method used. Without adjustment for dose errors the excess odds ratio was 1.51 Gy⁻ (95% CI 0.53, 3.86), which was reduced by 13% when regression-calibration adjustment was used, 1.31 Gy⁻ (95% CI 0.47, 3.31). A Monte Carlo maximum likelihood method yielded an excess odds ratio of 1.48 Gy⁻ (95% CI 0.53, 3.87), about 2% lower than the unadjusted analysis. The Bayesian method yielded a maximum posterior excess odds ratio of 1.16 Gy⁻ (95% BCI 0.20, 4.32), 23% lower than the unadjusted analysis. There were borderline significant (p = 0.053–0.078) indications of downward curvature in the dose response, depending on the adjustment methods used. There were also borderline significant (p = 0.102) modifying effects of gender on the radiation dose trend, but no significant modifying effects of age at time of accident, or age at screening as modifiers of dose response (p>0.2).ConclusionsIn summary, the relatively small contribution of unshared classical dose error in the current study results in comparatively modest effects on the regression parameters.     

Thyroid cancer incidence among Chernobyl emergency workers: follow-up period 1986-2003

A vast amount of research articles devoted to the increase in childhood thyroid cancer incidence in the most contaminated by radionuclides territories of Belarus, Russia and Ukraine affected by the Chernobyl accident were published recent years. However, the amount of research studies of thyroid cancer incidence among the Chernobyl emergency workers (liquidators) is quite scanty. In the article results of the study of thyroid cancer incidence in the cohort of the Chernobyl liquidators (103427 persons) residing in 6 administrative regions of Russia (North-West, Volgo-Vyatsky, Central-Chernozemny, Povolzhsky, North-Caucasus and Urals) are described and discussed. For the period 1986-2003 eighty seven cases of thyroid cancer were detected in the cohort. Statistically significant excess of the incidence among liquidators over baseline incidence, SIR = 3.39 (95% CI: 2.73; 4.16), among men of Russia has been found. The highest thyroid cancer incidence (SIR = 6.49) was registered among liquidators who had been involved in mitigation works during April-July 1986. At the same time no statistically significant relationship between the incidence rate and external radiation dose, ERR = 1.68 (95% CI: -0.95; 6.46), was detected.     

Cancer incidence and mortality in people aged less than 75 years: Changes in Australia over the period 1987–2007

BackgroundAustralia has one of the highest rates of cancer incidence worldwide and, despite improving survival, cancer continues to be a major public health problem. Our aim was to provide simple summary measures of changes in cancer mortality and incidence in Australia so that progress and areas for improvement in cancer control can be identified.MethodsWe used national data on cancer deaths and newly registered cancer cases and compared expected and observed numbers of deaths and cases diagnosed in 2007. The expected numbers were obtained by applying 1987 age–sex specific rates (average of 1986–1988) directly to the 2007 population. The observed numbers of deaths and incident cases were calculated for 2007 (average of 2006–2008). We limited the analyses to people aged less than 75 years.ResultsThere was a 28% fall in cancer mortality (7827 fewer deaths in 2007 vs. 1987) and a 21% increase in new cancer diagnoses (13,012 more diagnosed cases in 2007). The greatest reductions in deaths were for cancers of the lung in males (?2259), bowel (?1797), breast (?773) and stomach (?577). Other notable falls were for cancers of the prostate (?295), cervix (?242) and non-Hodgkin lymphoma (?240). Only small or no changes occurred in mortality for cancers of the lung (female only), pancreas, brain and related, oesophagus and thyroid, with an increase in liver cancer (267). Cancer types that showed the greatest increase in incident cases were cancers of the prostate (10,245), breast (2736), other cancers (1353), melanoma (1138) and thyroid (1107), while falls were seen for cancers of the lung (?1705), bladder (?1110) and unknown primary (?904).ConclusionsThe reduction in mortality indicates that prevention strategies, improvements in cancer treatment, and screening programmes have made significant contributions to cancer control in Australia since 1987. The rise in incidence is partly due to diagnoses being brought forward by technological improvements and increased coverage of screening and early diagnostic testing.     

Marked increase in breast cancer incidence in young women: A 10-year study from Northern Iran, 2004–2013

IntroductionBreast cancer is the most frequent cancer among women worldwide. Breast cancer incidence in young women is a health issue of concern, especially in middle-income countries such as Iran. The aim of this study is to report the breast cancer incidence variations in Golestan province, Iran, over a 10-year period (2004–2013).MethodsWe analyzed data from the Golestan Population-based Cancer Registry (GPCR), which is a high-quality cancer registry collecting data on primary cancers based on standard protocols throughout the Golestan province. Age-standardized incidence rates (ASRs) and age-specific incidence rates per 100,000 person-years were calculated. Time trends in ASRs and age-specific rates were evaluated using Joinpoint regressions. The average annual percentage change (AAPC) with correspondence 95% confidence intervals (95%CIs) were calculated.ResultsA total of 2106 new breast cancer cases were diagnosed during the study period. Most cases occurred in women living in urban areas: 1449 cases (68%) versus 657 cases (31%) in rural areas. Statistically significant increasing trends were observed over the 10-year study period amongst women of all ages (AAPC = 4.4; 95%CI: 1.2–7.8) as well as amongst women in the age groups 20–29 years (AAPC = 10.0; 95%CI: 1.7–19.0) and 30–39 years (AAPC = 5.1; 95%CI: 1.4–9.0).ConclusionThe incidence of breast cancer increased between 2004 and 2013 in Golestan province amongst all age groups, and in particular amongst women aged 20–39 years. Breast cancer should be considered a high priority for health policy making in our community.     

Cancer in adolescents and young adults: National incidence and characteristics in Japan

ObjectiveAdolescents and young adults (AYA) with cancer are confronted with unique challenges in areas of paramount concern within their age group, such as fertility, education, career, and delayed and long-term effects of treatment. However, the extent and depth of the problem has never been examined in the Japanese population. The aim of this study was to describe the status of cancer patients in the AYA population, using data from the hospital-based cancer registry (HBCR).Study designPatients included in the HBCR from January 2011 to December 2014 were included in this study to evaluate the incidence and cancer distribution trends among AYA. The total number and the proportion of AYA (15–39 years of age) stratified by sex, age, and cancer type were obtained. The incidence of age-specific cancer among AYA was also calculated.ResultsWe identified 30,394 male (35.1%) and 56,100 female (64.9%) cancer patients in the population, which collectively constituted about 3% of all invasive cancer cases. The incidence of cancer in AYA was estimated as 86.2 per 100,000 per year, and increased with age. The most affected population was women between 35 and 39 years of age (35%). Breast cancer was the most common type of cancer, followed by cervical, uterine, and thyroid cancers.ConclusionA substantial number of AYA are diagnosed with cancer every year. The distribution of cancer types in AYA was dependent on age and sex. These diversities in cancer types can inform researchers and policy makers to fine-tune their studies and policies.     

Thyroid cancer incidence among liquidators of the Chernobyl accident

The increase of thyroid cancer incidence rate among children living in the Chernobyl contaminated territories of Belarus, Russia and Ukraine has widely been accepted. Our current work deals with thyroid cancer incidence in the cohort of liquidators (99024 persons) living in 6 regions of Russia: North-West, Volgo-Vyatsky, Central-Chernozemny, Povolzhsky, North-Caucasus and Urals. In the period 1986-1998, a total of 58 thyroid cancer cases were detected in this cohort. We found a statistically significant increase of the thyroid cancer incidence rate in liquidators as compared to the baseline (male population of Russia) level (SIR=4.33, 95% CI: 3.29; 5.60). It was demonstrated that there is no dependence of incidence rates due to external radiation exposure (ERR/Gy=-2.23, 95% CI: -4.67; 0.22).     

Comparison of female breast cancer between Russia and Germany: A population-based study on time trends and stage at diagnosis

ObjectivesWhile a mammography-screening program (MSP) is being offered systematically in Germany since 2009, the dispanserizatsiya has been implemented in Russia since 2013. This study examined trends of stage at breast cancer diagnosis in two Russian regions and compared the results with the development in Germany. In addition, we aimed to gain further insights into the early detection of breast cancer in Russia.MethodsIncidence data from two cancer registries in Russia and 12 population-based cancer registries in Germany were used to analyse breast cancer incidence rates among women above age 30 over time. Further, we calculated rate ratios to compare the age group-specific incidence rates after the implementation of MSP in Germany (2010–2014) with the period before implementation (2003–2005) separately for each tumour stage and all stages combined.ResultsDuring the study period from 2003 to 2014, age-standardised rates for breast cancer were 54.6 and 116.7 per 100,000 for Russia and Germany, respectively. The proportion of the T1 stage at diagnosis among Russian women aged 50 + is half than that in Germany. Nevertheless, we observed an increasing trend of early-stage alongside the reduction of advanced-stage incidence rates of breast cancer in Russia.ConclusionsThe observed trend in Russia may reflect overall positive changes in early detection of breast cancer, with actual proportion of T1 stage still far behind Germany. Advances in breast cancer screening efforts through the dispanserizatsiya may help to further reduce the breast cancer burden.     

Screening effects in risk studies of thyroid cancer after the Chernobyl accident

In this article scenarios have been developed, which simulate screening effects in ecological and cohort studies of thyroid cancer incidence among Ukrainians, whose thyroids have been exposed to ¹³¹I in the aftermath of the Chernobyl accident. If possible, the scenarios were based on directly observed data, such as the population size, dose distributions and thyroid cancer cases. Two scenarios were considered where the screening effect on baseline cases is either equal to or larger than that of radiation-related thyroid cancer cases. For ecological studies in settlements with more than ten measurements of the ¹³¹I activity in the human thyroid in May–June 1986, the screening bias appeared small (<19%) for all risk quantities. In the cohort studies, the excess absolute risk per dose was larger by a factor of 4 than in the general population. For an equal screening effect on baseline and radiation-related cancer (Scenario 1) the excess relative risk was about the same as in the general population. However, a differential screening effect (Scenario 2) produced a risk smaller by a factor of 2.5. A comparison with first results of the Ukrainian–US-American cohort study did not give any indication that a differential screening effect has a marked influence on the risk estimates. The differences in the risk estimates from ecological studies and cohort studies were explained by the different screening patterns in the general population and in the much smaller cohort. The present investigations are characterized by dose estimates for many settlements which are very weakly correlated with screening, the confounding variable. The results show that under these conditions ecological studies may provide risk estimates with an acceptable bias.     

Major Factors Affecting Incidence of Childhood Thyroid Cancer in Belarus after the Chernobyl Accident: Do Nitrates in Drinking Water Play a Role?

One of the major health consequences of the Chernobyl Nuclear Power Plant accident in 1986 was a dramatic increase in incidence of thyroid cancer among those who were aged less than 18 years at the time of the accident. This increase has been directly linked in several analytic epidemiological studies to iodine-131 (¹³¹I) thyroid doses received from the accident. However, there remains limited understanding of factors that modify the ¹³¹I-related risk. Focusing on post-Chernobyl pediatric thyroid cancer in Belarus, we reviewed evidence of the effects of radiation, thyroid screening, and iodine deficiency on regional differences in incidence rates of thyroid cancer. We also reviewed current evidence on content of nitrate in groundwater and thyroid cancer risk drawing attention to high levels of nitrates in open well water in several contaminated regions of Belarus, i.e. Gomel and Brest, related to the usage of nitrogen fertilizers. In this hypothesis generating study, based on ecological data and biological plausibility, we suggest that nitrate pollution may modify the radiation-related risk of thyroid cancer contributing to regional differences in rates of pediatric thyroid cancer in Belarus. Analytic epidemiological studies designed to evaluate joint effect of nitrate content in groundwater and radiation present a promising avenue of research and may provide useful insights into etiology of thyroid cancer.     

Radiation-epidemiological studies of thyroid cancer incidence among children and adolescents in the Bryansk oblast of Russia after the Chernobyl accident (1991–2001 follow-up period)

In this study, thyroid cancer incidence (follow-up period: 1991–2001) has been analyzed, including persons who were exposed as children at an age between 0 and 17 years and who are living in the Bryansk oblast, the worst contaminated area of Russia after the Chernobyl accident. According to the census of 1989, the population of this oblast comprises 375 thousand people. Thyroid doses from incorporated radioiodine isotopes—both for the thyroid cancer cases and the study population—were determined based on the official methodology approved by the Russian Scientific Commission on Radiation Protection. Between 1991 and 2001, a total of 199 thyroid cancer cases were diagnosed at cancer centers (the so-called oncological dispensaries) of the investigated regions. The performed analysis relies on medical and dosimetric information available from the Russian National Medical and Dosimetric Registry which was established after the Chernobyl accident. Diagnoses were confirmed histologically for 95% of the cases. The analysis described revealed statistically significant radiation risk only for those exposed as children at an age of 0–9 years. In this group, the standardized incidence ratio (the national incidence rate was used as a reference) in the considered time period is estimated to be 6.7 (5.1, 8.6 95%CI) and 14.6 (10.3, 20.2 95%CI) for girls and boys, respectively. The risk dependence on age at exposure has also been studied. It has been shown that the smaller the age the higher the risk. For girls whose age at exposure was 0–4 years, the excess relative risk per 1 Gy for the period 1991–2001 was 45.3 (5.2, 9,953 95%CI; with internal control) and 28.8 (4.3, 2,238 95%CI; with external control), respectively. For boys whose age at exposure was 0–9 years the corresponding excess relative risk per 1 Gy was 68.6 (10.0, 4,520 95%CI) and 177.4 (−276, 10⁶ 95%CI), respectively. Dependence of radiation risk on time was studied, with the focus on two follow-up periods 1991–1996 and 1997–2001, respectively. In 1997–2001 the radiation risk is shown to decrease among girls, and increase among boys.     

Increased incidence of thyroid cancer in Latina,Italy: A possible role of detection of subclinical disease

ObjectiveTo describe the thyroid cancer incidence trends and geographical patterns in the Latina Province of Lazio, Italy using the population-based cancer registry.MethodsWe extracted from the Latina cancer registry all cases of thyroid cancer from 1997 to 2006. Cases were classified according to morphological type and diameter. Data for diagnostic procedures for Latina Province residents from 2001 to 2006 were extracted from the regional outpatient procedures information system.ResultsA total of 982 cases were diagnosed, for a standardized incidence of 8.3 and of 27.9 per 100,000 in males (n, 220) and in females (n, 762), respectively. The annual percent change (APC) was +16.7% (95% CI +7.2, +27.2) and +10.5% (95% CI +6.5, +14.6) in males and females, respectively. The increase was mostly due to papillary (n, 759) and small (≤20 mm) cancers (n, 617), with no difference by age (<45 years; n, 431). The APC of neck ultrasound performed was +8.7% (95% CI +0.1, +18.1) and +9.0% (95% CI +1.1, +17.4) and that of biopsy/cytology was +17.0% (95% CI +13.0, +21.3) and +16.6% (95% CI +6.2, +28.1) in men and women, respectively. The geographic pattern of biopsy/cytology was similar to that of cancer incidence but not to that of neck ultrasound.ConclusionsIn Latina, the increase in thyroid cancer incidence was more rapid than in the rest of Italy, particularly for types with a good prognosis. While tumor size and histotype suggest an increase in detection instead of an increase in disease occurrence, data on diagnostic procedure reimbursements cannot provide an explanation.