Income differences in screening, incidence, postoperative complications, and mortality of thyroid cancer in South Korea: a national population-based time trend study

Hee-Yeon Kang,Young-Ho Khang,Yeon-Yong Kim,Jinwook Bahk,Ikhan Kim

doi:10.1186/s12885-020-07597-4

Abstract

BackgroundThe incidence of thyroid cancer (TC) has increased rapidly over the past few decades in Korea. This study investigated whether the TC epidemic has been driven by overdiagnosis.MethodsWe calculated the TC screening rate from mid-2008 through mid-2014, and the incidence, postoperative complication, and mortality rates of TC between 2006 and 2015, using data from the Korea Community Health Survey, the National Health Insurance Database, and the cause-of-death data of Statistics Korea. Trends in age-standardized rates of all indicators were examined, along with income gaps therein. Analyses were conducted for lung cancer and stroke as negative control outcomes.ResultsThe incidence rate of TC increased from 46.6 per 100,000 to 115.0 per 100,000 between 2006 and 2012, and then decreased to 63.5 per 100,000 in 2015. Despite these remarkable changes in incidence, mortality did not fluctuate during the same period. High income was associated with high rates of screening, incidence, and postoperative complications, while low income showed an association with a high mortality rate. Analyses using negative control outcomes showed that high income was associated with low rates of both incidence and mortality, which contrasted with the patterns of TC. The recent decreases in TC incidence and postoperative complications, which reflect societal concerns about the overdiagnosis of TC, were more pronounced in high-income individuals than in low-income individuals.ConclusionsThe time trends in income gaps in screening, incidence, postoperative complications, and mortality of TC, as well as negative control outcomes, provided corroborating evidence of TC overdiagnosis in Korea.

Highlights

The incidence of thyroid cancer (TC) has increased rapidly over the past few decades in Korea
Increases in TC incidence rates with concomitant lack of changes in TC mortality rate have been considered as evidence for TC overdiagnosis [1,2,3,4]
The magnitudes of the screening, incident, postoperative complications, and deaths cases of TC were much higher for women than men

Summary

Introduction

The incidence of thyroid cancer (TC) has increased rapidly over the past few decades in Korea. Thyroid cancer (TC) incidence has increased in many countries around the world over the last few decades [1,2,3]. Its incidence in South Korea (hereafter ‘Korea’) has soared to an epidemic level [4,5,6]. Increases in TC incidence rates with concomitant lack of changes in TC mortality rate have been considered as evidence for TC overdiagnosis [1,2,3,4]. Concerns about the overdiagnosis of TC have been raised in Korea. In 2014, the problem of the increase in TC incidence received media attention in Korea [9]. A debate continues over the overdiagnosis of TC in Korea [12]

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Discussion

Conclusion