Education and Income Do Not Impact Temporal Trends of Papillary and Follicular Thyroid Cancer Incidence in Denmark—But What Does?

Clinical ThyroidologyVol. 34, No. 6 Thyroid CancerFree AccessEducation and Income Do Not Impact Temporal Trends of Papillary and Follicular Thyroid Cancer Incidence in Denmark—But What Does?Ulla Feldt-RasmussenUlla Feldt-Rasmussen Department of Medical Endocrinology and Metabolism, Rigshospitalet (Copenhagen University Hospital), Copenhagen, Denmark Department of Clinical Medicine, Faculty of Health and Clinical Sciences, Copenhagen University, Copenhagen, DenmarkSearch for more papers by this authorPublished Online:13 Jun 2022https://doi.org/10.1089/ct.2022;34.253-255AboutSectionsPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail Review of: Sørensen SM, De la Cour CD, Maltesen T, Urbute A, Kjaer SK 2022 Temporal trends in papillary and follicular thyroid cancer incidence from 1995 to 2019 in adults in Denmark according to education and income. Thyroid. Epub 2022 Apr 22. PMID: 35459415.SUMMARYBackgroundThyroid cancer is the most common endocrine malignancy worldwide (1). The most frequently found histologic subtypes are papillary thyroid cancer (PTC) and follicular thyroid cancer (FTC). Worldwide, the number of new thyroid cancer cases has increased remarkably during the past three decades, from approximately 95,000 cases in 1990 to 250,000 cases in 2017. In Denmark, the overall incidence of thyroid cancer, as well as of PTC and FTC, also increased substantially from 1980 to 2014 (2). One meta-analysis reported the increase to be due primarily to more cases of small papillary carcinomas (3), but the reason for the increase is still not fully understood. The aim of the present study (1) was to assess the temporal trends in PTC and FTC incidence in adults in Denmark during a period of 25 years according to level of education and income. For PTC, the trends were also stratified by tumor size according to socioeconomic status.MethodsDanish nationwide health registries hold validated and accurate information on cancer diagnoses, medical history, and socioeconomic variables, with virtually complete coverage of the population. All Danish citizens are assigned a unique 10-digit civil registration number at birth or migration into Denmark, enabling individual-level linkage of data between registries. The Danish Cancer Registry contains information on nearly all primary incident cancers diagnosed in Denmark since 1987. Information includes date of birth, sex, age at diagnosis, and tumor characteristics (topography, morphology, and T stage of the TNM system). Age-standardized incidence rates were calculated according to sex, tumor size, education, and income, and estimated incidence trends were calculated by average annual percentage change and corresponding 95% confidence intervals for the periods 1995–2004 and 2005–2019 using Poisson regression models.ResultsThe study identified 3454 cases of PTC and 972 cases of FTC. From 2005 to 2019 among women, the incidence of PTC increased across all levels of education (average annual percentage change (AAPC)short education, 12.5%; 95% CI, 9.8–15.3; AAPCmedium education, 8.1%; 95% CI, 6.4–9.9; AAPClong education, 7.3%; 95% CI, 5.4–9.2). The same pattern was seen for income. The incidence of FTC increased at all levels of education (AAPCshort education, 10.5%; 95% CI, 5.8–15.4; AAPCmedium education, 4.0%; 95% CI, 0.9–7.3; AAPClong education, 4.3%; 95% CI, 0.6–8.1), with the same pattern for income. Similar trends were observed among men, in both small (≤2 cm) and large (>2 cm) PTCs and from 1995 to 2004 in both sexes.ConclusionsThe Danish study demonstrated enhanced detection of thyroid cancers among all levels of education and income, but there were no significant relationships. In addition, the authors conclude that the results may suggest a true increase in the incidence of differentiated thyroid cancer.COMMENTARYThis study on thyroid cancer incidence and its relationship to socioeconomic status has taken advantage of the unique Danish public registries, of which the Danish Cancer Registry was the first worldwide. All information in the Danish registries is linked to individual personal numbers and is, therefore, unique in the combination of data for any person. In this study, the main outcome was socioeconomic status, for which the authors found no relationship (1), in agreement with the data from other countries (4). Other outcomes were the epidemiology before and after the implementation of iodine supplementation (5) and size of the thyroid cancer. All are, however, subgroups of the Danish thyroid cancer cohort through the period (2,5), since entrance into the Danish Cancer Registry is obligatory. Iodine plays a role in thyroid cancer incidence, but even more so in the distribution between the aggressive follicular and the more benign papillary thyroid cancers (6). How iodine influences thyroid cancer incidence is unclear. Iodine-deficient animals develop pituitary thyrotropin (TSH) stimulation and are at highest risk for thyroid cancer (7). In a human population, even a cautious increase in iodine intake results in increased thyroid autoimmunity, which in turn elevates serum TSH levels (8). Thus, Hashimoto thyroiditis has often been associated with an increased incidence of thyroid cancer (9,10). Finally, insulin resistance, high body-mass index, growth factors, and diabetes may also be contributing factors (11).In my clinical practice, I do not see an association between thyroid cancer incidence and socioeconomic status. However, rather than studying a limited predictive factor such as socioeconomic status, I would have preferred to see a study from valid population registries (e.g., from the Nordic countries) of a variety of predictors for thyroid cancer , in order to account for confounding comorbidities and address biases and the statistical power of multiple comparisons.Disclosures: The author has no relevant conflicts of interest to disclose.References1. Sørensen SM, De la Cour CD, Maltesen T, Urbute A, Kjaer SK 2022 Temporal trends in papillary and follicular thyroid cancer incidence from 1995 to 2019 in adults in Denmark according to education and income. Thyroid. Epub 22 Apr 2022. Link, Google Scholar2. 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Franchini F, Palatucci G, Colao A, Ungaro P, Macchia PE, Nettore IC 2022 Obesity and thyroid cancer risk: An update. Int J Environ Res Public Health 19:1116. Crossref, Google ScholarFiguresReferencesRelatedDetails Volume 34Issue 6Jun 2022 Information© Copyright 2022, Mary Ann Liebert, Inc.To cite this article:Ulla Feldt-Rasmussen.Education and Income Do Not Impact Temporal Trends of Papillary and Follicular Thyroid Cancer Incidence in Denmark—But What Does?.Clinical Thyroidology.Jun 2022.253-255.http://doi.org/10.1089/ct.2022;34.253-255Published in Volume: 34 Issue 6: June 13, 2022PDF download