Incidence pattern of thyroid cancer in Norway: influence of birth cohort and time period

The comparison of microbial communities in thyroid tissues from thyroid carcinoma patients

Thyroid carcinoma is a common endocrine organ cancer associated with abnormal hormone secretion, leading to the disorder of metabolism. The intestinal microbiota is vital to maintain digestive and immunologic homeostasis. The relevant information of the microbial community in the gut and thyroid, including composition, structure, and relationship, is unclear in thyroid carcinoma patients. A total of 93 samples from 25 patients were included in this study. The results showed that microbial communities existed in thyroid tissue; gut and thyroid had high abundance of facultative anaerobes from the Proteobacteria phyla. The microbial metabolism from the thyroid and gut may be affected by the thyroid carcinoma cells. The cooccurrence network showed that the margins of different thyroid tissues were unique areas with more competition; the stabilization of microcommunities from tissue and stool may be maintained by several clusters of species that may execute different vital metabolism processes dominantly that are attributed to the microenvironment of cancer.

Circular RNA profiling reveals a potential role of hsa_circ_IPCEF1 in papillary thyroid carcinoma

Circular RNAs (circRNAs) are a novel type of non‑coding RNAs that are expressed across species and are implicated in cellular biological processes, displaying dysregulated expression in various tumorigeneses. Therefore, circRNA deregulation could be a crucial event in thyroid carcinoma. The present study identified circRNA signatures in several patients with papillary thyroid carcinoma (PTC) to complement the understanding of PTC pathogenesis. Using microarray technology, the circRNA profiles in three pairs of PTC tumors and matching adjacent normal tissues were screened. Differentially expressed circRNAs were further validated by reverse transcription‑quantitative PCR in whole blood from 57 pairs of subjects. Bioinformatics data analyses including miRNA response element prediction, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway, competing endogenous RNA and KEGG Orthology‑Based Annotation System analyses were performed to predict circRNA associations with cancer‑related putative downstream miRNAs and target genes. Receiver operating characteristic curves and the area under the curve (AUC) values were acquired to assess the performance of validated circRNAs in predicting potential associations with PTC. In total, 158 dysregulated circRNAs were identified in PTC tumors relative to adjacent normal tissues. Notably, one downregulated circRNA (hsa_circ_IPCEF1) showed the preferable predictive power (AUC=0.8010, P<0.0001) and interactions with four cancer‑related genes (CASR, CDC25B, NFκB1 and SHOC2). From these analyses, one PTC‑related miRNA (hsa‑miR‑3619‑5p) was identified as a potential target for hsa_circ_IPCEF1 sponging, indicating the hsa_circ_IPCEF1/hsa‑miR‑3619‑5p axis in pathogenesis.

MicroRNA-9-5p functions as a tumor suppressor in papillary thyroid cancer via targeting BRAF

MicroRNAs (miRNAs/miRs) are widely studied as key regulators of gene expression and are involved in various diseases by affecting the miRNA-mediated regulatory function. BRAF is an important oncogene in the regulation of cell proliferation and apoptosis. In the present study, reverse transcription-quantitative polymerase chain reaction was used to determine the expression levels of miR-9-5p and BRAF mRNA in patients with papillary thyroid cancer (PTC). Western blotting was used to detect BRAF protein level. A luciferase assay was used to verify the miR-9-5p target site in BRAF. Cell Counting Kit-8 and flow cytometry were used to assess cell proliferation, and apoptosis, respectively. In the present study, it was demonstrated that miR-9-5p is downregulated in malignant PTC. Using bioinformatics analysis, miR-9-5p was predicted to target the human BRAF 3'-untranslated region (3'-UTR). A dual-luciferase assay demonstrated that miR-9-5p downregulated BRAF expression by directly targeting its 3'-UTR. Mutations in the 3'-UTR of BRAF completely abolished its interaction with miR-9-5p. Expression of exogenous miRNA that mimics miR-9-5p miRNA decreased BRAF protein and mRNA levels, while suppression of endogenous miR-9-5p resulted in an increase in BRAF protein, and mRNA levels. Furthermore, regulation of miR-9-5p was observed to suppress the viability of PTC cells by inducing apoptosis. Consistently, downregulation of miR-9-5p promoted proliferation of PTC cells by inhibiting the apoptosis of cells. In conclusion, the present study demonstrated that miR-9-5p may perform an important role in PTC prognosis and therapy.

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.

'Incidental' and 'non-incidental' thyroid papillary microcarcinomas are two different entities

OBJECTIVE

Papillary thyroid microcarcinomas (microPTC) may be 'incidental' (Inc-microPTC), occasionally found at histology after surgery for benign disease or 'non-incidental' (Non-Inc-microPTC), diagnosed on clinical grounds. It is unclear whether these different microPTC reflect the same disease. The aim of the study was to compare Inc-microPTC and Non-Inc-microPTC for clinical and histological features as well as for serum TSH, a known factor involved in PTC development.

DESIGN

We evaluated histology and serum TSH levels of consecutive patients submitted to thyroidectomy for goiter with compressive symptoms or for cytological diagnosis suspicious/indicative of PTC.

METHODS

In total, 665 consecutive patients (259 with a single thyroid nodule, SN and 406 with a multinodular gland, MN) were included in the study. According to histology, patients were classified as: benign nodular goiter (Benign, n=291); Inc-microPTC (n=92); Non-Inc-microPTC (n=67) and PTC≥1cm (macroPTC, n=215).

RESULTS

Inc-microPTC were significantly more frequent in MN than in SN (66/406, 16.2% vs 26/259, 10.0%, P=0.02). Patients with Inc-microPTC compared with Non-Inc-microPTC were older (mean age±s.d. 53.3±13.2 years vs 44.9±14.8 years, P=0.0002), had a smaller tumor size (median 4mm vs 9mm, P<0.0001), a higher frequency of multifocality (70/92, 76.1% vs 35/67, 52.2% P=0.001) and lower levels of TSH (median 0.6mIU/L, IR: 0.4-1.0mIU/L vs value 1. mIU/L, IR: 0.6-1.4mIU/L vs P=0.0001).

CONCLUSION

Incidental and non-incidental papillary thyroid microcarcinomas appear to be two different entities.

Recent trends in incidence, geographical distribution, and survival of papillary thyroid cancer in France

BACKGROUND

Over the past few decades, the incidence of thyroid cancer has dramatically increased in many countries. This increase was mainly seen in papillary cancer. The role of diagnostic practices and the effects of other risk factors were suggested to explain this increase. We provide a descriptive analysis in terms of changes in incidence, geographical distribution, and survival to check the relevance of assumptions about the increase.

METHODS

A detailed analysis of changes in incidence recorded in French cancer registries between 1982 and 2010 was performed taking into account age, period, and birth cohort. The geographical distribution of the incidence in the 2006-2010 period was estimated from the standardized incidence ratios. The net survival was estimated to evaluate the effects of sex, age, and period of diagnosis in patients diagnosed between 1989 and 2004 and followed-up until 2013.

RESULTS

The incidence of papillary cancer has increased sharply over the 1982-2010 period; the average annual rate of increase was 7.8% in men and 7.2% in women. The increase has slowed in the recent period in people aged less than 50 at the time of diagnosis. It has also slowed in the cohorts born 1945 and after. There was a strong geographic disparity in incidence between areas covered by cancer registries. Finally, the net survival was very high; the 10-year net survival was 96% and improved progressively from 82% in patients diagnosed between 1989 and 1993 to 95% in those diagnosed between 1999 and 2004.

CONCLUSION

The increased incidence results most probably from the effect of medical practice, although other risk factors seem also involved, but to a lesser extent. The increase seems to have slowed down in the recent years, especially in the youngest age groups. This observation suggests a recent trend towards saturation of the effects of medical practices in post-1945 cohorts associated with an effect of the gradual dissemination of the recommendations relative to the management of thyroid nodules.

Thyroid microcarcinoma

Nowadays the most commonly occurring differentiated thyroid cancer in many countries is a microcarcinoma in patients older than 45 years, incidentally found during neck ultrasound. In view of their low morbidity and mortality, the crucial point is how to manage such microcarcinomas. Recently published European and American guidelines aim to minimize the diagnostic and therapeutic procedures without affecting the diagnostic accuracy and the therapeutic effectiveness, keeping in mind that we are dealing with patients who have a normal life expectancy and to whom we have to guarantee an excellent quality of life. The present review will summarize the clinical and pathological features of thyroid microcarcinoma, including its definition, prevalence, presentation, pathology, genetic, clinical impact and will try to derive from them a rationale for therapeutic and diagnostic intervention.

Thyroid microcarcinoma

Nowadays the most commonly occurring differentiated thyroid cancer in many countries is a microcarcinoma in patients older than 45 years, incidentally found during neck ultrasound. In view of their low morbidity and mortality, the crucial point is how to manage such microcarcinomas. Recently published European and American guidelines aim to minimize the diagnostic and therapeutic procedures without affecting the diagnostic accuracy and the therapeutic effectiveness, keeping in mind that we are dealing with patients who have a normal life expectancy and to whom we have to guarantee an excellent quality of life. The present review will summarize the clinical and pathological features of thyroid microcarcinoma, including its definition, prevalence, presentation, pathology, genetic, clinical impact and will try to derive from them a rationale for therapeutic and diagnostic intervention.

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.

Increasing incidence of differentiated thyroid cancer in South East England: 1987-2006

There has been a worldwide increase in the incidence of thyroid cancer (TC). Documenting these recent trends is of immense value to cancer control measures, monitoring policies, improving clinical outcomes, resource allocation and stimulating research. Hence this study aimed to analyse the changes in incidence, staging and morphologic types of TC in South East England (1987-2006) by means of a retrospective, descriptive epidemiological study using anonymized data obtained from the Thames Cancer Registry (TCR) of all patients registered with TC in the period 1987-2006. Ethical approval was obtained from the Kent Research Ethics Committee. 4,880 anonymized datasets using the ICD-10 code for thyroid cancer (C73) were analyzed using SPSS v.17. TC was commoner amongst females 3,560 (73%) than males 1,320 (27%) with a 2.7:1 ratio. Mean age at diagnosis was 53 years (Range 5-99) years. An increasing incidence trend was observed in early stage disease (p < 0.001), in young adults aged ≤ 49 years (p < 0.001) and in well-differentiated TC (papillary p < 0.001 and follicular p = 0.03). The results showed that TC is commoner in females than males in SE England with a 2.7:1 ratio. The results also indicate that TC incidence has increased in SE England over the 20 years studied, with the greatest increase occurring in early stage disease, in females, young adults and well-differentiated types (papillary and follicular). This may be due to widespread usage of ultrasound with detection of incidental nodules. Further studies are required to explain the trend.

Incidence of thyroid cancer in Italy, 1991-2005: time trends and age-period-cohort effects

BACKGROUND

In Italy, some of the highest incidence rates (IRs) of thyroid cancer (TC) worldwide have been reported.

PATIENTS AND METHODS

TC cases <85 years of age reported to Italian cancer registries during 1991-2005 were included. Age-standardized IRs were computed for all TC and age-period-cohort effects were estimated for papillary TC.

RESULTS

IRs of TC were twofold higher in 2001-2005 than in 1991-1995 (18 and 8 per 100,000 women, 6 and 3 per 100,000 men, respectively). Increases were similar in the two sexes and nearly exclusively due to papillary TC. Increases of papillary TC by birth cohort were found in both sexes and among all age groups between 20 and 79 years. Age-period-cohort models showed a strong period effect in both sexes (rate ratio for 2001-2009 versus 1991-1995 = 2.5 in women and 2.3 in men), although IRs peaked at an earlier age in women (45-49 years) than men (65-69 years).

CONCLUSION

The strength of the period effect in both sexes and the earlier onset in women than men strongly implicated increased medical surveillance in the upward trends of papillary TC incidence in Italy. The consequences of the current intense search for TC on morbidity and possible overtreatment, especially among young women, should be carefully evaluated.

International patterns and trends in thyroid cancer incidence, 1973-2002

During the past several decades, an increasing incidence of thyroid cancer has been reported in many parts of the world. To date, no study has compared the trends in thyroid cancer incidence across continents. We examined incidence data from cancer incidence in five continents (CI5) over the 30-year period 1973-2002 from 19 populations in the Americas, Asia, Europe, and Oceania. Thyroid cancer rates have increased from 1973-1977 to 1998-2002 for most of the populations except Sweden, in which the incidence rates decreased about 18% for both males and females. The average increase was 48.0% among males and 66.7% among females. More recently, the age-adjusted international thyroid cancer incidence rates from 1998 to 2002 varied 5-fold for males and nearly 10-fold for females by geographic region. Considerable variation in thyroid cancer incidence was present for every continent but Africa, in which the incidence rates were generally low. Our analysis of published CI5 data suggests that thyroid cancer rates increased between 1973 and 2002 in most populations worldwide, and that the increase does not appear to be restricted to a particular region of the world or by the underlying rates of thyroid cancer.

Time trends for thyroid cancer in northwestern Spain: true rise in the incidence of micro and larger forms of papillary thyroid carcinoma

BACKGROUND

Thyroid cancer incidence is increasing throughout the world. Most studies attribute this rise entirely to the increase in papillary carcinoma, the most common thyroid malignancy in iodine-sufficient areas. A variety of nonetiological factors such as changes in clinical practice may affect the incidence of thyroid cancer and some researchers have suggested that this rise is only apparent due to an increase in diagnostic activity. Since data on the epidemiology of thyroid cancer in Spain are scarce, the main goal of this study was to analyze changes in thyroid cancer presentation, incidence, and prevalence in Vigo (northwestern Spain) between 1978 and 2001, and to investigate the relationship between the incidence rates and trends in tumor size and thyroid surgery.

METHODS

In this descriptive epidemiologic study, an analysis was carried out on new thyroid cancer cases obtained from the Pathology Registry of the University Hospital of Vigo (500,000 inhabitants). Trends in age, sex, thyroid surgery, histological type, tumor size, and incidence rates were calculated. The prevalence of thyroid cancer was determined in three cross-sectional surveys.

RESULTS

The rate of population undergoing thyroid surgery significantly increased over time. Out of 322 new primary thyroid cancers, papillary thyroid cancer (PTC) was the predominant type (76%). The age-standardized incidence rate shows a significant increase in females: 1.56 per 100,000 year (1978 to 1985) to 3.83 (1986 to 1993) and 8.23 (1994 to 2001); and in males: 0.33, 1.19, and 2.65, respectively. PTC was mainly responsible for this pattern and was the result of both the increase in micropapillary thyroid carcinoma (MPTC) incidence and in PTC measuring more than 1 cm. Besides MPTC cases, no significant variations were observed in tumor size over time.

CONCLUSIONS

In northwestern Spain, the incidence of thyroid cancer is increasing. These data should be taken into account when planning health resources for these patients. Our results may reflect the contribution that other factors, besides increased diagnostic activity, have made to the rise in thyroid cancer incidence in our region. Additional studies are needed to explain the rise in PTC incidence throughout the world and to search for potential risk factors that are currently unrecognized.

What is New on Thyroid Cancer Biomarkers

Thyroid cancer harbours in about 5% of thyroid nodules. The majority of them are well-differentiated cancers originating from the follicular epithelium, and are subdivided into papillary and follicular carcinomas. Undifferentiated carcinomas and medullary thyroid carcinomas arising from C cells are less common.

Although most thyroid nodules are benign, distinguishing thyroid cancer from benign lesions is crucial for an appropriate treatment and follow-up. The fine needle aspiration cytology (FNAC) allows the diagnosis of nature of thyroid nodules in the majority of cases. However, FNAC has some limitations, particularly in the presence of follicular lesions which can appear dubious in rare instances even at histology.

In an effort to improve diagnostic accuracy and offer new prognostic criteria, several immunohistochemical and molecular markers have been proposed. However, most of them have to be validated on large series before being used in routine practice.

Clinical features and therapeutic implication of papillary thyroid microcarcinoma

Papillary thyroid microcarcinomas (PTMs) are small tumors (< or =1 cm of diameter) that belong to the well-differentiated low-risk carcinomas of the thyroid, which are characterized by benign behavior, probably of little clinical significance, and do not affect patients' survival. They are found in otherwise normal thyroids or in multinodular goiters with a clinical frequency varying substantially according to different series. Sometimes, PTM may be associated with lymph node metastases at presentation and/or locoregional recurrences during follow-up. Distant metastases are extremely rare, but have been reported. Although deaths related to PTM are almost unknown, PTM raises therapeutic implications. This review addresses the issue of definition, treatment, and follow-up of PTM.

Estimating infra-national and national thyroid cancer incidence in France from cancer registries data and national hospital discharge database

OBJECTIVE

As in many countries, cancer registries cover only part of the population in France. Incidence/mortality ratio observed in registries is usually extrapolated to produce national estimates of cancer incidence. District-level estimates are not currently available. For cancer sites such as thyroid, the incidence/mortality ratio widely varies between districts, and alternative indicators must be explored. This study aims to produce national and district-level estimations of thyroid cancer incidence in France, using the ratio between incidence and hospital-based incidence.

METHODS

Analyses concerned population living in France and aged over 20, for the period 1998-2000. For each sex, number of incident cases were analysed according to number of surgery admissions for thyroid cancer (Poisson model) in the districts covered by a registry. Age was included in the model as fixed effect and district as random effect. The model's ability to predict incidence was tested through cross-validation. The model was then extrapolated to produce national incidence estimations, and for women, district-level estimations.

RESULTS

The national estimations of incidence rate age-standardised on the world population were 3.1 [95% prediction interval: 2.8-3.4] for men and 10.6 [9.8-11.4] for women, corresponding respectively to 1,148 [1,042-1,264] and 4,104 [3,817-4,413] annual new cases. For women, district-level incidence rates presented wide geographical variations, ranging broadly from 5 to 20 per 100,000. These estimations were quite imprecise, but their imprecision was smaller than the extent of geographical disparities.

CONCLUSION

National incidence estimations obtained are relatively precise. District-level estimations in women are imprecise and should be treated carefully. They are informative though regarding the extent of geographical disparities. The approach can be useful to improve national incidence estimates and to produce district-level estimates for cancer sites presenting a high variability of the incidence/mortality ratio.

Increasing incidence of thyroid cancer in Basilicata: an Italian study

OBJECTIVE

In recent years many authors have reported an increase in thyroid cancer (TC) incidence in several countries. The cause of such phenomenon remains unclear.

DESIGN

This study was designed to estimate the incidence of TC in Basilicata, the smallest region of Southern Italy with a population of 596,546 people, between 2001 and 2004.

MAIN OUTCOME

A total of 302 cases of TC were identified. The annual incidence of TC changed over the years, from 10.0 per 100,000 people in 2001 to 15.7 per 100,000 people in 2004. The number of new TC cases per 100,000 people increased an average of 16% per yr. Median age at diagnosis was 49 yr. The most frequent histotype was papillary TC (PTC) (73.2%). In 20 (6.6%) patients with PTC, we identified at least one first-degree relative affected by differentiated TC.

CONCLUSIONS

The present study shows a high incidence of sporadic and familial non-medullary TC in Basilicata. The reason for this finding may be related to several factors discussed in the paper. Further studies evaluating the trends in the incidence of TC in Basilicata in the future could provide some answers for the potential pathogenetic hypothesis.

Time trends and geographic variations for thyroid cancer in New Caledonia, a very high incidence area (1985-1999)

Thyroid cancer incidence in New Caledonia is the highest reported in the world and is approximately 10-fold higher than in most developed countries. We describe the incidence patterns in this country according to histological and sociodemographic characteristics to give clues about potential etiologic factors. Another objective is to see whether the incidence figures are related to enhanced detection of small size carcinomas. The study included all 498 cases of thyroid cancer diagnosed in 1985-1999. Pathology reports were systematically reviewed to determine the histological type of the tumor and the size of the cancerous nodules. The incidence of carcinomas < or =10 mm was taken as an indicator of enhanced detection due to improved screening procedures. The age-standardized incidence rates in 1985-1999 were exceptionally high in Melanesian women (71.4/100,000) and men (10.4/100,000). The incidence increased three-fold in women from 1995 onwards. The increase in incidence was more striking for papillary carcinomas < or =10 mm than for large size carcinomas, but an increased incidence of carcinomas >10 mm was also observed among women. The analysis by municipality of residence in Melanesian women showed that the incidence was twice as high in 1995-1999 in the Loyalty Islands as in the rest of the country. The sharp increase of thyroid cancer incidence in 1985-1999 in New Caledonia was partly related to enhanced detection of small size carcinomas. The elevated incidence of thyroid cancers, as well as the ethnic and geographic disparities, may result from common environmental or lifestyle risk factors that need to be identified.

A time trend analysis of papillary and follicular cancers as a function of tumour size: a study of data from six cancer registries in France (1983-2000)

The incidence of thyroid cancers, and in particular the papillary forms, has been increasing sharply for many years in Western countries. However, the factors explaining this increase have not been clearly established. Some studies mention the effects of radioactive fallout, particularly after the accident in Chernobyl. Another probable cause is related to progress in medical practice, and particularly in diagnosis. In this article, we describe time trends in the incidence of papillary and follicular cancers, taking into account the size of the tumour at the time of diagnosis. The analysis was carried out on cases from six French cancer registries for the period 1983-2000. Anatomopathological reports concerning 3381 cancer cases were systematically recoded and centralised, following ICDO-3 rules. Over the whole period, the annual percent change of the incidence of papillary cancers was +8.13% and +8.98%, respectively in men and in women. For micropapillary carcinomas (< or = 10 mm), this increase was respectively +12.05% and +12.85%. There is no significant effect of period apart from micropapillary carcinomas in women. However, a birth cohort effect exists for some groups. This effect corresponds to an acceleration in the risk for people born after the 1930s. For the most recent period (1998-2000), half the cases of papillary cancer were micropapillary carcinomas, and for one third of these, the tumour was < or = 5 mm. Our description of a time trend of incidence as a function of tumour size supports the hypothesis of the role of medical practice in a context of high prevalence. Obviously, these findings do not exclude the possible role of other factors.

Variation in relative survival of thyroid cancers in Europe: Results from the analysis on 21 countries over the period 1983–1994 (EUROCARE-3 study)

We described the relative survival of thyroid cancer cases diagnosed in Europe during the period 1990-1994 and analysed time trends in relative survival during the period 1983-1994 using the EUROCARE-3 database. Relative survival of thyroid cancers is one of the highest amongst cancer sites, with age-standardised relative survival rates of 74% in men and 82% in women over the period 1990-1994, with marked differences between countries. The higher relative survival rates are observed in Scandinavian countries and the lower rates are observed in the UK and the countries of Eastern Europe. Relative survival is higher in women than in men, and decreases with age whatever the histological group. There are significant differences in relative survival according to histological type. Relative survival has slightly increased over the period 1983-1994 only when all histological types have been considered together. Time trend was, however, non-existent when the different histological groups were taken into account except during the most recent period of observation. One possible explanation for the differences in relative survival between countries and sex may probably be found in the changes in thyroid classification and diagnosis techniques. When these changes are not homogeneous, the distribution of thyroid cancers by histology and by stage at diagnosis may be very different. The only way to understand these differences is to conduct specific studies including a description of stage at diagnosis, diagnosis procedures used for staging and details of treatment.

Unexpected additional increase in the incidence of thyroid cancer among a recent birth cohort in Switzerland

Data collected by the Swiss Cancer Registries Network (ASRT/VSKR) have been used to analyse trends in thyroid cancer during the last available 20 years, to make within-country geographical comparisons for current incidence rates. Age-standardized (European population) incidence rates per 100,000 for all morphologies combined ranges from 1.62 to 2.99 among males and from 2.13 to 8.09 among females in Switzerland. Regression analyses for both sexes combined detected an increase in time for papillary cases and a decrease for other types. Age-period-cohort analyses revealed that the youngest cohorts of men and women born after 1940 had an increased risk of all types of thyroid cancer while the cohort of people born between 1920 and 1939 were at increased risk of the papillary subtype. Assuming a higher sensitivity to ionizing radiation among the youngest people, a Chernobyl effect cannot be definitively excluded and continuous study of this topic should be encouraged.

Changing trends in incidence and mortality of thyroid cancer in Scotland

OBJECTIVE

The incidence of thyroid cancer is increasing in several countries. The aim was to investigate trends in the incidence and mortality of thyroid cancer in Scotland, where thyroid cancer is relatively uncommon, between 1960 and 2002.

DESIGN

Descriptive epidemiological study.

METHODS

Thyroid cancer registrations between 1960 and 2000 were obtained from the Scottish Cancer Registry. Mortality data (1960-2002) and population estimates were supplied by the Registrar General for Scotland. Incidence and mortality data are expressed as age-specific rates and European age-standardized rates (EASRs).

RESULTS

Thyroid cancer was three times more common in females than in males and was more common in older than younger age groups. Between 1960 and 2000, the annual EASR of thyroid cancer increased from 1.76 to 3.54 per 100,000 for females (P < 0.001) and from 0.83 to 1.25 per 100,000 in males (P < 0.001). The overall thyroid cancer increase between 1975 and 2000 was primarily caused by an increase in papillary thyroid cancer, particularly over the most recent decade. The incidence of follicular thyroid cancer also increased while the incidence of anaplastic and medullary thyroid cancer did not change significantly. Mortality from thyroid cancer fell progressively between 1960 and 2002. EASR for females decreased from 1.05 to 0.28 (P < 0.001) and in males from 0.73 to 0.34 (P < 0.001). For both sexes, in general, survival at 1-, 5- and 10-year follow-up intervals from diagnosis improved steadily over the study period. In both females and males, survival from thyroid cancer was better if the diagnosis was made under the age of 50 years.

CONCLUSIONS

Thyroid cancer incidence has increased in Scotland over the past 40 years. This is accompanied by a change in the distribution of histological type with a particular increase in papillary carcinoma. The reasons for this may relate partly to changes in clinical practice and histological criteria. Falling mortality in the face of increasing incidence reflects improvements in survival, which should improve further with the introduction and implementation of standardized treatment protocols.

Descriptive epidemiology of thyroid carcinoma in Carinthia, Austria: 1984-2001. Histopathologic features and tumor classification of 734 cases under elevated general iodination of table salt since 1990: population-based age-stratified analysis on thyroid carcinoma incidence

INTRODUCTION

The aim of the study was to investigate the current thyroid carcinoma (TC) incidence in Carinthia, a former iodine-deficient, goiter-endemic region in Austria with approximately 550,000 inhabitants from 1984 to 2001. Using age-cohort analysis we analyzed the TC incidence under the impact of two regional risk factors: the contamination of Austrian soils by the radioactive fallout in from Chernobyl 1986 and the increased iodination of table salt in a general program of goiter prophylaxis begun in 1991. To evaluate the characteristics of TC incidence, we compared the results of the periods 1984-1989, 1990-1995, and 1996-2001.

RESULTS

A total of 734 TC cases were diagnosed. Papillary, follicular, medullary, oxyphilic, and anaplastic TC accounted for 76%, 18%, 3%, 1%, and 2%, respectively. The female to male ratio was 3:1. The annual incidence rate increased by 8.05% in females and 11.6% in males. TC cases younger than 40 years of age accounted for 22.6%, with a rate increase of 18% per year in young males, the female-to-male ratio decreased from 8.3, 6.1, 2.7 younger than 40 in the compared periods. Along with a further increase in papillary TC incidence and papillary thyroid carcinoma (PTC) follicular thyroid carcinoma (FTC) ratio in the adult population, the ratio tended to decrease in the younger than 40-year-old population. T4 class TC and loco-regional lymph node involvement increased significantly.

INTERPRETATION

The observed changes in TC incidence, particularly in the young population, as in adults, could be linked to the abovementioned risk factors involved in the initiation and early growth of TC, and iodine may play a role in stimulating overall thyroid activity.

Controversies in papillary microcarcinoma of the thyroid

Papillary thyroid carcinomas that are smaller than 1 cm are classified as papillary microcarcinomas (PMC). These lesions are frequently detected as incidental findings on autopsy or in surgical specimens. They are often multifocal. The relationship between PMC and clinical papillary thyroid carcinoma (PTC) is not clear. In patients with clinical thyroid cancer, PMC may represent intrathyroidal metastases; they may be the earliest form of future large lesions. These uncertainties raise questions about appropriate clinical management of patients with these lesions. Review of the literature substantiates the argument that clinically evident PTC may be distinctly different from solitary or multifocal PMC in terms of etiology and biologic behavior, supporting a conservative approach to management.

Incidence of thyroid cancer in adults recorded by French cancer registries (1978-1997)

This article analyses time trends and geographical variations of thyroid cancer by histological type. Incidence data were provided by 8 French cancer registries over the period 1978-1997, with 3853 adult cases reported. To assess the effects of age, period, cohort and area on incidence, log-linear Poisson regression models were used. Thyroid cancer increased exponentially from the cohort born in 1925. This increase was essentially due to papillary cancer, which increased by 6.2% per year in men and 8.1% per year in women over the entire period (1978-1997). In women, the recent trends were significantly different between the studied geographical areas. The analysis shows that the increase in thyroid cancer, essentially of the papillary type, is not recent. It may be attributed to a possible screening effect or to an increase in the number of "incidentally" discovered cases linked to the use of modern diagnostic tools.

Increasing thyroid cancer incidence in Canada, 1970-1996: time trends and age-period-cohort effects

We examined time trends in thyroid cancer incidence in Canada by age, time period and birth cohort between 1970 and 1996. Age-specific incidence rates by time period and birth cohort were calculated and age-period-cohort modelling used to estimate effects underlying the observed trends. Overall age-adjusted incidence rates of thyroid cancer doubled, from 3.3 and 1.1 per 100 000 in 1970-72 to 6.8 and 2.2 per 100 000 in 1994-96, among females and males respectively. Almost all the increase between 1970-72 and 1994-96 was due to papillary carcinoma of the thyroid. Age, birth cohort and period effects significantly improved the fit of the model for females, while age and birth cohort effects were significant determinants of the incidence among males. There were significant differences in the patterns/curvature for age, period and birth cohort effects between women and men. Our results suggest that the increases in thyroid cancer incidence in Canada may be associated with more intensive diagnostic activities and change in radiation exposure in childhood and adolescence. Temporal changes in reproductive factors among young women may explain some of the gender differences observed.

Trends in treatment and long-term survival of thyroid cancer in southeastern Netherlands, 1960-1992

Thyroid cancer (TC), comprising less than 1% of all cancers in the Netherlands, has a good prognosis in general. Controversy still remains on the extent of surgical treatment and the indication for additional Iodine-131 (131I) therapy in the management of differentiated TC. The aim of this study was to describe (changes in) the treatment of TC and to determine independent prognostic factors for crude and relative survival of differentiated TC diagnosed in general hospitals. This population-based, retrospective study was based on data from the Eindhoven Cancer Registry, Comprehensive Cancer Centre South (I.K.Z.), Eindhoven, the Netherlands. Data were collected on all 343 TC patients diagnosed from 1 January 1960 to 31 December 1992. All available information on treatment (initial and additional) and survival (on 1 April 1994) were recorded. Initial surgical treatment was defined as limited or extended. Multivariate analysis of crude and relative survival to determine prognostic factors for differentiated TC was performed. Mean follow-up was 7.6 years. The proportion of patients with differentiated TC increased from 60% in 1960-1972 to 84% in 1985-1992. TC patients were treated in all hospitals in the region, approximately 2-4/year. Ninety per cent of all TC patients initially underwent surgical treatment; the extended procedures increasing from 27% in 1960-1974 to 61% in 1985-1992. 131I was also administered increasingly (from 18-44%) to patients with differentiated TC. The relative 5, 10 and 20 year survival rates for all TC were 80, 75 and 75%, respectively. In the first 5 years after diagnosis the crude death ratio was higher with the rise of age and for the follicular type and after 5 years for males and advanced disease. After inclusion of surgical treatment into the model, the estimates of the other death ratios did not change. Patients treated with 131I did better only during the first 5 years. Although the prognosis for TC patients treated in general hospitals in Southeastern Netherlands was similar to that found for patients treated in referral centres, concentration of treatment should be considered.

Incidence and clinical characteristics of thyroid carcinoma after iodine prophylaxis in an endemic goiter country

Iodized salt prophylaxis has been performed in Austria since 1963. Through this approach, mean urinary iodine excretion has been normalized to 144+/-23.5 microg/g creatinine per day. Thus Tyrol is no longer an endemic goiter area. We have analyzed the impact of iodized salt prophylaxis on thyroid cancer (TC) comparing data from the early 1960s with those corresponding to the period 1986 to 1995, when iodine supply was normalized. The study included 439 patients from Tyrol and Southern Tyrol. The incidence of TC in Tyrol has risen during the past decades from 3.07 between in 1957 and 1970 to 7.8 between 1990 and 1994 (CR/100000/year). We observed a rise in the percentage of differentiated adenocarcinomas (56% to 91.5%) with a predominance of papillary TC (54.4%) along with a decrease of anaplastic TC. In addition to these histological features, a shift to less advanced TNM stages, eg, T1-3, N0-1a, M0, was obvious, increasing from 29% to 72.2%, whereas advanced tumors, ie, T4 or N1b or M1, decreased from 71% to 28%. These changes have significantly improved prognosis. The current 5-year survival rate is 90.7% as compared with a rate of 73% in the 1960s; the values for 7-year survival are 89% and 48%, respectively. The marked effects of age, tumor stages, and histology on prognosis were confirmed with the Kaplan-Meier method. We conclude that together with normalization of iodine supply in an endemic goiter region the epidemiological profile of TC has changed. Even though the incidence of TC has risen, prognosis has significantly improved due to a shift towards differentiated forms of TC that are diagnosed at earlier stages.

Time trend and age-period-cohort effect on incidence of thyroid cancer in Connecticut, 1935-1992

Recent studies from Europe suggest a continuing increase in thyroid cancer, but it is unclear whether this trend also applies to the United States. The current study examined the long-term trend of thyroid cancer in Connecticut. Our results show that the overall age-adjusted incidence rate of thyroid cancer has been increasing in Connecticut, from 1.30/100,000 in 1935-1939 to 5.78/100,000 in 1990-1992 in females, and from 0.30/100,000 in 1935-1939 to 2.77/100,000 in 1990-1992 in males. The increase mainly comes from papillary carcinoma of the thyroid. The birth cohort analyses indicate that the increase in thyroid cancer occurred among cohorts born between 1915 and 1945, which experienced an increase of 31.4% every 5 years in males and 17.3% in females over the period 1960-1979. For those born since the 1945 cohort, the incidence has been decreasing, at rates of 9.3% and 8.3% every 5 years over the period 1975-1992 in males and females, respectively. Age-period-cohort modeling results also suggest a strong birth cohort effect on the observed time trend in both sexes, which closely follows the introduction of radiation treatment of benign childhood conditions in the head and neck between 1920 and the 1950s in the United States. Our results are consistent with the suggested radiation hypothesis, indicating that radiation treatment of benign childhood conditions in the head and neck is largely responsible for the observed increase of thyroid cancer in Connecticut.