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

Current Iodine Nutrition Status and Morbidity of Thyroid Nodules in Mainland China in the Past 20 Years

The aim of this study was to comprehensively assess the prevalence of goiter and thyroid nodules (TNs) in relation to China's iodine nutrition level over the past 20 years and provide an effective reference for developing health policies. PubMed, EMBASE, Chinese National Knowledge Infrastructure, Chongqing VIP, and Chinese Wan Fang databases were searched for relevant studies from Jan 1996 to Feb 2020. Two reviewers extracted valid data from the eligible citations to determine the morbidity of TNs in different urinary iodine concentrations (UICs) and in patients of different genders, of different ages, who live in different geographic regions, and who live at different altitudes, as well as the P values of interactions between groups. There were 26 articles (34 studies) included in this analysis. The overall morbidity of TNs in mainland China was 23.4%. Morbidity was higher in urban areas (P < 0.001) than in rural and mixed areas. Coastal areas (P < 0.001), female patients (P < 0.001), high-altitude areas (P < 0.001), and residence in south China (P < 0.001) were all associated with higher morbidity of TNs. The lowest morbidity value of TNs, 16%, was in the more-than-adequate iodine subgroup. The highest morbidity, 27.2%, was in the adequate iodine subgroup. The morbidity of TNs increases with age, and women are more likely to have TNs. We also need to perform more epidemiological studies, and in the future, we should cultivate better understanding of the relationship between other thyroid diseases and provide more comprehensive and useful information for other researchers.

Role of the cytopathologist during the procedure of fine-needle aspiration biopsy of thyroid nodules

Purpose

This study aimed to conduct a diagnostic and cost-effective analysis of the cytopathology assistance in the ultrasound (US)-guided fine-needle aspiration biopsy (FNAB) for characterising thyroid nodules.

Materials and methods

We reviewed the reports relative to 9061 US-guided FNABs for the histologic definition of the nature of thyroid nodules: 45.4% completed with the cytopathologist assistance and 54.6% by the radiologist alone.

We also performed the cost-effectiveness analysis (CEA) of the procedure with and without the cytopathologist assistance.

Results

We found a significant positive correlation between the adoption/non-adoption of cytopathologist assistance and the number of indeterminate (TIR1) (Chi-square; z-score, Z = 10.22; critical value 5%, C = 1.96; p < 0.001). The cytopathologist's absence was correlated with the number of TIR 1 (Pearson correlation, product–moment correlation r = 0.059; critical value 5%, C = 0.008; p < 0.001).

The total cost of the model's cytopathologist-assistance branch is 109.87€, while the total cost of the non-cytopathologist-assistance branch is 95.08€.

Conclusion

The cytopathologist assistance resulted in fewer nondiagnostic results, thus excluding the procedure's repetition but involved a higher expense, mainly due to the professional cost of the pathologist's participation. These data may provide decision-makers in healthcare with a practical evidence based on the opportunity to include the cytopathologist assistance in the thyroid nodule's FNAB depending on the available resources and the population's expectance.

Supplementary information

The online version contains supplementary material available at 10.1186/s13244-021-01053-y.

Position paper from the Japan Thyroid Association task force on the management of low-risk papillary thyroid microcarcinoma (T1aN0M0) in adults

The incidence of thyroid carcinoma has been increasing worldwide. This is interpreted as an increase in the incidental detection of papillary thyroid microcarcinomas (PTMCs). However, mortality has not changed, suggesting overdiagnosis and overtreatment. Prospective clinical trials of active surveillance for low-risk PTMC (T1aN0M0) have been conducted in two Japanese institutions since the 1990s. Based on the favorable outcomes of these trials, active surveillance has been gradually adopted worldwide. A task force on the management of PTMC in adults organized by the Japan Thyroid Association therefore conducted a systematic review and has produced the present position paper based on the scientific evidence concerning active surveillance. This paper indicates evidence for the increased incidence of PTMC, favorable surgical outcomes for low-risk PTMC, recommended criteria for diagnosis using fine needle aspiration cytology, and evaluation of lymph node metastasis (LNM), extrathyroidal extension (ETE) and distant metastasis. Active surveillance has also been reported with a low incidence of disease progression and no subsequent recurrence or adverse events on survival if conversion surgery was performed at a slightly advanced stage. Active surveillance is a safe and valid strategy for PTMC, because it might preserve physical quality of life and reduce 10-year medical costs. However, some points should be noted when performing active surveillance. Immediate surgery is needed for PTMC showing high-risk features, such as clinical LNM, ETE or distant metastasis. Active surveillance should be performed under an appropriate medical team and should be continued for life.

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.

Changing incidence and projections of thyroid cancer in mainland China, 1983-2032: evidence from Cancer Incidence in Five Continents

PURPOSE

An increasing incidence of thyroid cancer has been seen in China during the past several decades. The aim of this study was to analyze potential age, period, and cohort effects on the incidence of thyroid cancer in mainland China and to predict new cases up to 2032.

METHODS

We calculated age-adjusted and age-specific incidence rates of thyroid cancer, conducted an age-period-cohort analysis of 35,037 thyroid cancer incidence cases reported to Cancer Incidence in Five Continents from 1983 to 2012 in mainland China, and predicted incidence up to 2032 using the Bayesian age-period-cohort method.

RESULTS

The age-adjusted overall incidence rate of thyroid cancer increased from 1.93/100,000 in 1983-1987 to 12.18/100,000 in 2008-2012 among females and from 0.77/100,000 in 1983-1987 to 3.89/100,000 in 2008-2012 among males, with a female-to-male ratio of approximately 3.0 during the three decades. Strong birth cohort and period effects on the incidence of thyroid cancer were observed for both sexes, and such an increasing trend is predicted to continue for at least the next 20 years. More than 3.7 million new cases are projected in the 2028-2032 period.

CONCLUSION

The increasing trend of thyroid cancer in mainland China will cause a great burden in the future. In addition to the potential impact of improvement in medical diagnostics, potential exposure to risk factors have played a role in the observed rising trend. Further population-based epidemiologic studies are required to identify risk factors to aid in thyroid cancer prevention and control.

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.

Overdiagnosis and overtreatment of thyroid cancer: A population-based temporal trend study

BACKGROUND

The increase in incidence of thyroid cancer during the last decades without concomitant rise in mortality may reflect the growing detection of indolent forms of thyroid cancer, and may have fueled unnecessary thyroidectomies. Our aim was therefore, to compare recent secular trends in surgical intervention rate for thyroid cancer with the incidence and mortality of thyroid cancer to assess overdiagnosis and resulting overtreatment.

METHODS

We conducted a population-based temporal trend study in Switzerland from 1998 to 2012. All cases of invasive thyroid cancer, deaths from thyroid cancer, and cancer-related thyroidectomies were analyzed. We calculated changes in age-standardized thyroid cancer incidence rates, stratified by histologic subtype and tumor stage, thyroid cancer-specific mortality, and thyroidectomy rates.

RESULTS

Between 1998 and 2012, the age-standardized annual incidence of thyroid cancer increased from 5.9 to 11.7 cases/100,000 among women (annual mean absolute increase: +0.43/100,000/year) and from 2.7 to 3.9 cases/100,000 among men (+0.11/100,000/year). The increase was limited to the papillary subtype, the most indolent form of thyroid cancer. The incidence of early stages increased sharply, the incidence of advanced stages increased marginally, and the mortality from thyroid cancer decreased slightly. There was a three- to four-fold increase in the age-standardized annual thyroidectomy rate in both sexes.

CONCLUSIONS

We observed a large increase in the incidence of thyroid cancer, limited to papillary and early stage tumors, with a three- to four-fold parallel increase in thyroidectomy. The mortality slightly decreased. These findings suggest that a substantial and growing part of the detected thyroid cancers are overdiagnosed and overtreated.

IMPACT

Targeted screening and diagnostic strategies are warranted to avoid overdetection and unnecessary treatment of thyroid cancers.

An Approach to Macroscopic Central Lymph Nodes Detected during Surgery in Patients with Thyroid Micropapillary Carcinoma: Should We Resort to Dissection?

Background. High-resolution ultrasonography and the ability to perform fine-needle aspiration biopsy even for nodules smaller than three millimeters have considerably increased the detection rate of thyroid micropapillary carcinoma (TMPC). Despite favorable prognosis, the prevalence of cervical lymph node metastases in patients with TMPC is approximately 30%. Aim. In this study, we aimed to determine the central lymph node metastasis rate and its relation to the characteristics of the tumor. Methods. One hundred nine patients who underwent surgery due to TMPC between December 2009 and January 2014 were analyzed retrospectively. Patients were divided into two groups according to whether they underwent lymph node dissection and the two groups were then compared with respect to tumor size and multicentricity, age, and presence of lymphocytic thyroiditis. Results. There were no statistically significant differences between the two groups of patients in terms of tumor size, tumor multicentricity, age, and presence of lymphocytic thyroiditis. When the patient group that received lymph node dissection was further analyzed, it was found that patients with lymphocytic thyroiditis had a significantly lower number of metastatic lymph nodes. Conclusion. Central lymph node dissection in TMPC patients with macroscopic lymph node detected intraoperatively would ensure accurate staging without an increase in morbidity.

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.

The association between selenium and other micronutrients and thyroid cancer incidence in the NIH-AARP Diet and Health Study

BACKGROUND

Selenium is an essential trace element that is important for thyroid hormone metabolism and has antioxidant properties which protect the thyroid gland from oxidative stress. The association of selenium, as well as intake of other micronutrients, with thyroid cancer is unclear.

METHODS

We evaluated associations of dietary selenium, beta-carotene, calcium, vitamin D, vitamin C, vitamin E, folate, magnesium, and zinc intake with thyroid cancer risk in the National Institutes of Health - American Association of Retired Persons Diet and Health Study, a large prospective cohort of 566,398 men and women aged 50-71 years in 1995-1996. Multivariable-adjusted Cox proportional hazards regression was used to examine associations between dietary intake of micronutrients, assessed using a food frequency questionnaire, and thyroid cancer cases, ascertained by linkage to state cancer registries and the National Death Index.

RESULTS

With the exception of vitamin C, which was associated with an increased risk of thyroid cancer (HR(Q5 vs Q1), 1.34; 95% CI, 1.02-1.76; P(trend), <0.01), we observed no evidence of an association between quintile of selenium (HR(Q5 vs Q1), 1.23; 95% CI, 0.92-1.65; P(trend), 0.26) or other micronutrient intake and thyroid cancer.

CONCLUSION

Our study does not suggest strong evidence for an association between dietary intake of selenium or other micronutrients and thyroid cancer risk. More studies are needed to clarify the role of selenium and other micronutrients in thyroid carcinogenesis.

Continued rapid increase in thyroid cancer incidence in california: trends by patient, tumor, and neighborhood characteristics

BACKGROUND

Thyroid cancer incidence is increasing worldwide. Incorporating 22 years of incidence data through 2009, we extend examination of these trends among a wide array of subgroups defined by patient (age, sex, race/ethnicity, and nativity), tumor (tumor size and stage), and neighborhood (socioeconomic status and residence in ethnic enclaves) characteristics, to identify possible reasons for this increase.

METHODS

Thyroid cancer incidence data on 10,940 men and 35,147 women were obtained from the California Cancer Registry for 1988-2009. Population data were obtained from the 1990 and 2000 U.S. Census. Incidence rates and 95% confidence intervals (CI) were calculated and incidence trends were evaluated using Joinpoint regression to evaluate the timing and magnitude of change [annual percentage change (APC) and rate ratios].

RESULTS

The incidence of papillary thyroid cancer continues to increase in both men (APC, 5.4; 95% CI, 4.5-6.3 for 1998-2009) and women (APC, 3.8; 95% CI, 3.4-4.2 for 1998-2001 and APC, 6.3; 95% CI, 5.7-6.9 for 2001-2009). Increasing incidence was observed in all subgroups examined.

CONCLUSIONS

Although some variation in the magnitude or temporality of the increase in thyroid cancer incidence exists across subgroups, the patterns (i) suggest that changes in diagnostic technology alone do not account for the observed trends and (ii) point to the importance of modifiable behavioral, lifestyle, or environmental factors in understanding this epidemic.

IMPACT

Given the dramatic and continued increase in thyroid cancer incidence rates, studies addressing the causes of these trends are critical. Cancer Epidemiol Biomarkers Prev; 23(6); 1067-79. ©2014 AACR.

Recent trends in the incidence, geographical distribution, and survival from thyroid cancer in Wales, 1985-2010

BACKGROUND

Previous studies of thyroid cancer incidence in Wales have given varying results with suggestions of an excess of cases in geographic areas that were previously exposed to the radioactive fallout from the 1986 Chernobyl nuclear reactor incident. Our objective in this study was to provide an up-to-date comprehensive analysis of time trends in the incidence, geographical distribution, and survival from thyroid cancer in Wales.

METHODS

We identified thyroid cancer cases, registered from 1985 through 2010 in the Welsh Cancer Intelligence and Surveillance Unit (WCISU). Age standardized rates were determined from the European standard population. A Poisson regression model was fitted to assess temporal trends and rate ratios (RRs) and confidence intervals (CIs) were determined and compared across consecutive time periods: 1985-1997 and 1998-2010. Standardized incidence ratios were calculated for each of the 22 local authority areas. Relative survival and Kaplan-Meier curves were computed to analyze all cause and thyroid cancer-specific survival.

RESULTS

A total of 1747 thyroid cancer cases were registered from 1985 to 2010. Age standardized incidence rates were 2.8 and 1.2 per 100,000 population per year for females and males respectively. Incidence rates increased with time (RR 1.3 [CI 1.2-1.5], p < 0.001; 1998-2010 vs. 1985-1997). The incidence of papillary cancer increased progressively over the study period (RR 2.22 [CI 1.91-2.57], p < 0.001; 1998-2010 vs. 1985-1997), while rates for other (nonpapillary) histological subtypes remained static (RR 0.95 [CI 0.84-1.08], p = 0.45; 1998-2010 vs. 1985-1997). We identified two geographical areas of increased incidence, but the spatial distribution of cases was inconsistent with exposure to radioactive fallout. Five-year relative survival from all-cause mortality improved from 74.2 [CI 66.8-80.1] in 1985-1989 to 82.6 [CI 77.1-86.9] in 2000-2004, but remained poor for patients over the age of 65 years (p < 0.001, > 65 years vs. 15-64 years) and patients with anaplastic thyroid cancer (p < 0.001; anaplastic vs. other histological varieties).

CONCLUSIONS

The incidence of thyroid cancer has increased in Wales, predominantly due to an increase in papillary cancers. The current geographical distribution of cases does not support a radiation effect in the region. Survival has remained poor for patients over the age of 65 years and those with anaplastic carcinoma.

Controversies in primary treatment of low-risk papillary thyroid cancer

In many parts of the world, incidence of papillary thyroid cancer is increasing faster than any other malignancy. Most papillary thyroid cancers that are diagnosed are small and are generally regarded as being low risk, with little or no effect on mortality. Papillary thyroid cancer is a clinical challenge because it is difficult to prove benefit from the traditional therapeutic triad for this disorder (ie, total thyroidectomy with or without prophylactic central neck dissection, radioiodine remnant ablation, and suppression of serum thyroid-stimulating hormone with levothyroxine). However, risk of disease recurrence might be reduced by these therapies in a subset of patients with more aggressive disease. In the past decade, professional societies and other groups have established evidence-based clinical practice guidelines for management of papillary thyroid cancer, but these efforts have been made difficult by a paucity of randomised controlled trials. In this review, we summarise epidemiological data for disease incidence, discuss some controversies in disease management, and outline a therapeutic framework founded in the best available medical evidence and existing recommendations from clinical practice guidelines.

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

OBJECTIVE

To describe the thyroid cancer incidence trends and geographical patterns in the Latina Province of Lazio, Italy using the population-based cancer registry.

METHODS

We 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.

RESULTS

A 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.

CONCLUSIONS

In 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.

Dietary nitrate and nitrite and the risk of thyroid cancer in the NIH-AARP Diet and Health Study

During the past several decades, an increasing incidence of thyroid cancer has been observed worldwide. Nitrate inhibits iodide uptake by the thyroid, potentially disrupting thyroid function. An increased risk of thyroid cancer associated with nitrate intake was recently reported in a cohort study of older women in Iowa. We evaluated dietary nitrate and nitrite intake and thyroid cancer risk overall and for subtypes in the National Institutes of Health-American Association of Retired Persons (NIH-AARP) Diet and Health Study, a large prospective cohort of 490,194 men and women, ages 50-71 years in 1995-1996. Dietary intakes were assessed using a 124-item food frequency questionnaire. During an average of 7 years of follow-up we identified 370 incident thyroid cancer cases (170 men, 200 women) with complete dietary information. Among men, increasing nitrate intake was positively associated with thyroid cancer risk (relative risk [RR] for the highest quintile versus lowest quintile RR = 2.28, 95% confidence interval [CI]: 1.29-4.041; p-trend <0.001); however, we observed no trend with intake among women (p-trend = 0.61). Nitrite intake was not associated with risk of thyroid cancer for either men or women. We evaluated risk for the two main types of thyroid cancer. We found positive associations for nitrate intake and both papillary (RR = 2.10; 95% CI: 1.09-4.05; p-trend = 0.05) and follicular thyroid cancer (RR = 3.42; 95% CI: 1.03-11.4; p-trend = 0.01) among men. Nitrite intake was associated with increased risk of follicular thyroid cancer (RR = 2.74; 95%CI: 0.86-8.77; p-trend = 0.04) among men. Our results support a role of nitrate in thyroid cancer risk and suggest that further studies to investigate these exposures are warranted.

Increase incidence of thyroid cancer in Florianopolis, Brazil: comparative study of diagnosed cases in 2000 and 2005

OBJECTIVE

To provide epidemiological information about thyroid cancer (TC) in the Metropolitan area of Florianopolis and investigate some factors that could be associated with this type of cancer.

METHOD

This study analyzed data of patients who had TC diagnosed and underwent surgical treatment in 2000 and 2005. Epidemiological factors about patients, tumors and surgical procedures were evaluated.

RESULTS

In 2000 and 2005, an increasing incidence of TC at a rate of 132.33% was detected. The increased rate was mainly observed for tumors measuring less than 1 cm (p = 0.004). Results also showed an increase in the number of multifocal tumors (p = 0.02) and in the rate of total thyroidectomy (p = 0.002).

CONCLUSIONS

The increasing incidence of TC in the Metropolitan area of Florianopolis is probably due to more invasive thyroid nodule management. Future studies are necessary to establish potential predicting factors for papillary thyroid microcarcinoma aggressiveness, as well as predictors of follicular lesion malignancy to identifying more accurately the appropriate therapy approach.

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.

Do Polybrominated Diphenyl Ethers (PBDEs) Increase the Risk of Thyroid Cancer?

An increased incidence of thyroid cancer has been reported in many parts of the world including the United States during the past several decades. Recently emerging evidence has demonstrated that polyhalogenated aromatic hydrocarbons (PHAHs), particularly polybrominated diphenyl ethers (PBDEs), alter thyroid hormone homeostasis and cause thyroid dysfunction. However, few studies have been conducted to test whether exposure to PBDEs and other PHAHs increases the risk of thyroid cancer. Here, we hypothesize that elevated exposure to PHAHs, particularly PBDEs, increases the risk of thyroid cancer and may explain part of the increase in incidence of thyroid cancer during the past several decades. In addition, genetic and epigenetic variations in metabolic pathway genes may alter the expression and function of metabolic enzymes which are involved in the metabolism of endogenous thyroid hormones and the detoxification of PBDEs and other PHAHs. Such variation may result in different individual susceptibilities to PBDEs and other PHAHs and the subsequent development of thyroid cancer. The investigation of this hypothesis will lead to an improved understanding of the role of PBDEs and other PHAHs in thyroid tumorigenesis and may provide a real means to prevent this deadly disease.

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.

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.