INCIDENCE OF THYROID CANCER FROM SELECTED SOUTH AMERICA POPULATION-BASED CANCER REGISTRIES

Objectives: The aim of this study is to describe the thyroid cancer (TC) incidence trends and to analyze age-period-cohort (APC) effects in Cali (Columbia), Costa Rica, Goiânia (Brazil), and Quito (Ecuador). Methods: Data was obtained from the Cancer Incidence in Five Continents (CI5) series and the crude and age-standardized incidence rates (ASR) were calculated. Trends were assessed using the estimated annual percentage change (EAPC) and APC models were estimated using Poisson regression for individuals aged between 20 and 79 years. Results: An increasing trend in ASR was observed among women from Goiânia (9.2%), Costa Rica (5.7%), Quito (4.0%), and Cali (3.4%), and in men from Goiânia (10.0%) and Costa Rica (3.4%). The APC modeling showed that there was a period effect in all regions and for both sexes. Increasing rate ratios (RR) were observed among women over the periods. The best fit model in women was the age-periodcohort in all regions and in the same way in men from Quito, while the age-cohort model showed a better fit in men from Cali and Costa Rica and the age-drift model reached a better fit among men from Goiânia. Conclusions: These findings suggest that overdiagnosis is one of the possible explanations for the observed increasing pattern in thyroid cancer incidence. However, some environmental exposures may also have contributed to the observed increase.