B. C. James1, R. H. Grogan2, E. L. Kaplan2, P. Angelos2, B. Aschebrook-Kilfoy3 1Indiana University,Endocrine Surgery/Surgery/Indiana University,Indianapolis, INDIANA, USA 2University Of Chicago,Endocrine Surgery/Surgery/University Of Chicago,Chicago, IL, USA 3University Of Chicago,Department Of Public Health Sciences,Chicago, IL, USA
Introduction:
The incidence rate of thyroid cancer worldwide has been increasing at a dramatic rate. However, previous studies have shown that the rates in some countries appeared to be leveling off in recent years. We sought to evaluate recent trends in incidence rates and predict that these rates have continued to rise.
Methods:
Trends in the incidence rates of thyroid cancer were obtained from the WHO Cancer Incidence volumes 4-9, which contain incidence data reported by selected population-based cancer registries covering areas within Asia, Oceania, Africa, Europe, and the Americas between 1973 and 2007. Thyroid cancer classification was based on ICD-8, ICD-9, and ICD-10 for volumes 4,5-8,9-10, respectively. Percent change was calculated for each population to show the relative change in incidence rate by gender, histologic subtype, and mortality rate between 1973 and 2007.
Results:
Thyroid cancer rates increased from 1973 to 2007 for 18 of the 19 countries examined. The average increase in thyroid cancer incidence across populations was 88% in males and 108% in females. The largest increase was in New South Wales, Australia (266.67% in males and 365.22% in females). In contrast, thyroid cancer rates in Sweden decreased by 18% in males and 5% in females. Significant variation in incidence rates was present within every continent, and each country showed independent patterns of increase across continents. There was no correlation between underlying thyroid cancer incidence rates and the increase in incidence rate. A consistent ratio of three to one between females and males was observed in all populations at all time periods.
Conclusion:
This study has shown that there has been a global increase in thyroid cancer incidence rates between 1973 and 2007. Rates rose even in countries that are not technologically advanced, therefore we hypothesize that both environmental factor and detection bias are at play.