Thyroid cancer epidemiology in Northeast Spain, Girona: a population-based incidence trend study 1994 - 2020

Guan Cai, Wali
BACKGROUND: Thyroid carcinoma (TC) is the most prevalent malignant tumor within the endocrine system, experiencing a notable global incidence surge in recent decades, attributable to heightened detection of incidental tumors. Mortality rates have either decreased or remained stable, attributed to advancements in diagnostic techniques, particularly for papillary carcinoma. Techniques such as ultrasound, ultrasound-guided fine-needle aspiration and other imaging techniques for other clinical reasons have enhanced sensitivity in detecting small thyroid nodules. The epidemiological features of TCs are largely influenced by the increased identification of indolent cases, which suggests possible overdiagnosis. Therefore, our study aimed to provide an up-to-date assessment on the regional distribution of TC incidence during the period 1994 – 2020 in Girona (northeast region of Spain). OBJECTIVE: To describe and analyze incidence and trends of TC in Girona during the period 1994 -2020 by sex, age, histological type, and stage at diagnosis to check whether this data are similar to those observed in other countries and regions. METHODS: This research constitutes a population-based cross-sectional study. TC cases were obtained from the population-based Cancer Registry of Girona (GCR) between 1994 and 2020. All our cases were classified into 7 subtypes: papillary, follicular, medullary, oncocytic, anaplastic and poorly differentiated, other types and non-specified. We extracted age-standardised incidence rates (ASR) per 100 000 person-year and Annual Percentage Changes (APC) of TC, as defined by the International Classification of Disease for Oncology 3rd edition (code C73), for a northeast region of Spain (Girona) by sex and 5 age groups (0-14, 15-24, 25-49, 50-69, and ≥ 70 years) from GCR database. RESULTS: During the study period 1994 – 2020 we registered 1,149 diagnosed cases of TC in Girona province (76.85% in women). Mean age of diagnosis were 48.7 years ± 15.9. The most common histological type was papillary (80.4%), following by follicular (8.0%), medullary (4.8%), oncocytic (2.1%), anaplastic (2.1%). Global ASR was 6.42 per 100 000 inhabitants-year (95%CI: 6.05 – 6.81), representing 9.78 (95%CI: 9.14 - 10.46) in women and 3.06 (95%CI: 2.70 – 3.45) in men. Incidence trends significantly increased in global (APC +2.23%), primarily in women (APC: +2.41%), for papillary type (APC: +2.31%) in stage I of diagnosis (APC: +2.44%). Papillary carcinoma was the most common, representing the 80.4% of total cases, follicular 10.1% and medullary carcinoma in 4.8%. INTERPRETATION: These data showed an increasing trend in incidence of TC in Girona, especially in women between 1994 - 2020 years. Papillary carcinoma was the most common histological type. Our study is in accordance with the European trend in TC incidence and sex differences ​
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