Endocrine Abstracts

Background: The incidence and mortality rates of thyroid cancer (TC) vary across nations for reasons such as registry accuracy, diagnostic and management practices, care quality, and standardization methods. Risk factors for TC include genetic abnormalities, iodine intake, TSH levels, autoimmune thyroid disease, gender, lifestyle, and environmental pollutants. In 2005, a mandatory salt iodization program was implemented in Lithuania. This study aims to analyse TC incidence and mortality trends in Lithuania between 1990 and 2019.

Methods: All TC cases (ICD-10 code C73) reported to the Lithuanian Cancer Registry from 1990 to 2019 were used in this study. The Registry covers the entire population of Lithuania (2.79 million per 2019 census). Age-specific and age-standardized incidence and mortality rates were calculated using the direct method with the EU-27+EFTA reference population¹. A Joinpoint regression model was used to estimate the average annual percentage change (AAPC).

Results: Over a 30-year period, 7, 753 TC cases were diagnosed. The mean age of the patients was 53.57±15.22 years, 84% were women. The median follow-up duration was 11.5 years. The age-standardized incidence rate of TC in males ranged between 1.42 and 4.95/100, 000. AAPC increased significantly by 6.8% (95% CI 4.4, 28.2) in 1990–2004, and the changes in AAPC was insignificant at 1.8% (95% CI -10.7, 3.6) in 2004–2019. The age-standardized incidence rate in female ranged from 3.75 to 20.51 cases per 100, 000, with a significant increase in AAPC of 9.3% (95% CI 7.9, 10.8) in 1990–2004, and significant decrease in AAPC of 2.8% (95% CI -5.3, -0.1) in 2004–2019. The male mortality rate for TC ranged from 0.53 to 3.38/100, 000, with slight change in AAPC of 4.8% (95% CI -0.1, 25) in 1990–2002, and insignificant decrease in AAPC of 5.9% (95% CI -17.7, 3.2) in 2002–2019. In females it ranged from 0.7 to 5.38 cases per 100, 000, with a significant increase in AAPC of 4.2% (95% CI 2.3, 6.6) in 1990–2006 and a significant decrease in AAPC of 12.5% (95% CI -16.1, -9.8) in 2006–2019.

Conclusions: Incidence and mortality increased until the early 2000s, whith a stable or declining trend thereafter. Since 2006, there has been a marked decrease in mortality, especially in women, associated with the salt iodization program. Further studies are needed to confirm the link between salt iodization and reduction in mortality.

Reference: 1. Eurostat Methodologies and working papers. Revision of the European Standard Population, 2013 edition.