Sir.
I have read with great interest the paper published by Paz Cruz E et al. in the journal Heliyon 10 (2024) e23964 available online on December 21, 2023 [1]. The aim of this study is to describe the genetic variants of thyroid cancer present in the Ecuadorian population and the patterns of incidence and mortality of thyroid cancer in Ecuador in the period 2016 to 2021. This study reports that the incidence of thyroid cancer remained relatively stable at approximately 22 cases per 100,000 population between 2016 and 2019. In 2020, the incidence decreased to 14 cases per 100,000 population, rising again in 2021 to 19 cases per 100,000. The mortality rate was 0.91 ± 0.08 deaths per 100,000 population [1].
In 2020, worldwide the age-standardized incidence of thyroid cancer is 6.6/100,000 (females 10.1 and males 0.68/100,000), and the age-standardized mortality 0.4/100,000 (females 0.5 and males 0.3/100,000) [2]. However, there is great variability in thyroid cancer incidence rates between and within countries [3]. Since the early 1980s, an increase in incidence rates has been observed [3,4]. Increased detection of indolent thyroid cancers, with overdiagnosis accounting for up to 60–90 % of all patients diagnosed with thyroid cancer would be the underlying causes [3].
Incidence and mortality rates are usually estimated at the national level in each country, but caution is needed in the interpretation of the estimates. The quality of the country's own source data has an impact on the validity of the estimates, incomplete, inaccurate recording or late reporting of new cases and deaths may underestimate the measurements [3].
International estimates of incidence and mortality use appropriate methods and reliable sources of population-based data with sufficient completeness such as national tumor registries to estimate incidence, and national death registries to estimate mortality to obtain accurate and reliable results [2,5].
In the study by Paz Cruz E [1] although the authors acknowledge among the limitations of their paper that the database used (hospital discharge yearbook) "is not specifically designed to discriminate between multiple instances in which the same patient is admitted to and discharged from a hospital. In addition, it may not capture thyroid cancer cases that do not require hospitalization, creating a potential risk of case duplication." however, they do not take any statistical measures (– weighted regression methods, weighted survival analyses, etc. –) to adjust for the contribution of duplicate cases in the analysis. Nor do they perform a time series study to establish the trend of incidence and mortality of thyroid cancer, limiting themselves to citing rates in different periods of years erroneously interpreting this as an epidemiological trend.
An appropriate method for estimating the trend in the rates of different types of cancer is jointpoint regression analysis [6]. Rates are modeled using Joinpoint regression analysis and expressed as annual percent change (APC) and average annual percent change (AAPC). The final best-fit model with the estimated APC is selected based on a trend within each segment. AAPC estimation involves using the underlying Joinpoint model to calculate a summary measure over a pre-specified fixed interval. This allows a single number to be used to describe the average APC over several years. This is valid even if the Joinpoint model indicates changes in trends over those years. It is calculated as a weighted average of the APCs from the Joinpoint model with weights equal to the length of the APC interval. This analysis can be performed with software from the National Cancer Institute and is available online [7].
The use of adequate registries of new cases and overall deaths in the population will make it possible to clearly establish the real epidemiological characteristics of thyroid cancer in the population and will be a valuable contribution to establishing long-term health and economic strategies in the country.
CRediT authorship contribution statement
Enrique Lopez Gavilanez: Writing – review & editing. Mario Navarro Grijalva: Investigation.
Declaration of competing interest
The author declares no conflict of interest.
References
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