title: Association between screening and the thyroid cancer "epidemic" in South Korea: evidence from a nationwide study.
abstract: OBJECTIVE
  To investigate whether screening for thyroid cancer led to the current "epidemic" in South Korea.
  
  
  METHODS
  Review of the medical records of nationally representative samples of patients with a diagnosis of thyroid cancer in 1999, 2005, and 2008.
  
  
  METHODS
  Sample cases were randomly selected from South Korea's nationwide cancer registry, using a systematic sampling method after stratification by region.
  
  
  METHODS
  5796 patients with thyroid cancer were included (891 in 1999, 2355 in 2005, and 2550 in 2008).
  
  
  METHODS
  The primary outcome was age standardised incidence of thyroid cancer and the changes in incidence between 1999 and 2008 according to the methods used to detect tumours (screen detection versus clinical detection versus unspecified).
  
  
  RESULTS
  Between 1999 and 2008, the incidence of thyroid cancer increased 6.4-fold (95% confidence interval 4.9-fold to 8.4-fold), from 6.4 (95% confidence interval 6.2 to 6.6) per 100 000 population to 40.7 (40.2 to 41.2) per 100 000 population. Of the increase, 94.4% (34.4 per 100 000 population) were for tumours less than 20 mm, which were detected mainly by screening. 97.1% of the total increase was localised and regional tumours according to the Surveillance, Epidemiology, and End Results (SEER) summary stage. Where cases were clinically detected, 99.9% of the increased incidences (6.4 per 100 000 population) over the same period were tumours less than 20 mm.
  
  
  CONCLUSIONS
  The current "epidemic" of thyroid cancer in South Korea is due to an increase in the detection of small tumours, most likely as a result of overdetection. Concerted efforts are needed at a national level to reduce unnecessary thyroid ultrasound examinations in the asymptomatic general population.
authors.affiliation: National Cancer Control Institute, National Cancer Center, Goyang, Republic of Korea.|Department of Biostatistics, Yonsei University Graduate School of Public Health, Seoul, Republic of Korea.
authors.forename: Sohee
authors.initials: S
authors.lastname: Park
authors.affiliation: National Cancer Control Institute, National Cancer Center, Goyang, Republic of Korea.
authors.forename: Chang-Mo
authors.initials: CM
authors.lastname: Oh
authors.affiliation: National Cancer Control Institute, National Cancer Center, Goyang, Republic of Korea.|Department of Cancer Control and Policy, Graduate School of Cancer Science and Policy, National Cancer Center, Goyang, Republic of Korea.
authors.forename: Hyunsoon
authors.initials: H
authors.lastname: Cho
authors.affiliation: National Cancer Control Institute, National Cancer Center, Goyang, Republic of Korea jslee@ncc.re.kr.|Department of Preventive medicine, Yonsei University, College of Medicine, Seoul, Republic of Korea.
authors.forename: Joo Young
authors.initials: JY
authors.lastname: Lee
authors.affiliation: National Cancer Control Institute, National Cancer Center, Goyang, Republic of Korea.
authors.forename: Kyu-Won
authors.initials: KW
authors.lastname: Jung
authors.affiliation: National Cancer Control Institute, National Cancer Center, Goyang, Republic of Korea.|Department of Cancer Control and Policy, Graduate School of Cancer Science and Policy, National Cancer Center, Goyang, Republic of Korea.
authors.forename: Jae Kwan
authors.initials: JK
authors.lastname: Jun
authors.affiliation: National Cancer Control Institute, National Cancer Center, Goyang, Republic of Korea.|Department of Cancer Control and Policy, Graduate School of Cancer Science and Policy, National Cancer Center, Goyang, Republic of Korea.
authors.forename: Young-Joo
authors.initials: YJ
authors.lastname: Won
authors.affiliation: National Cancer Control Institute, National Cancer Center, Goyang, Republic of Korea.
authors.forename: Hyun-Joo
authors.initials: HJ
authors.lastname: Kong
authors.affiliation: National Cancer Control Institute, National Cancer Center, Goyang, Republic of Korea.|Department of Cancer Control and Policy, Graduate School of Cancer Science and Policy, National Cancer Center, Goyang, Republic of Korea.
authors.forename: Kui Son
authors.initials: KS
authors.lastname: Choi
authors.affiliation: Center for Thyroid Cancer, National Cancer Center, Goyang, Republic of Korea jslee@ncc.re.kr.
authors.forename: You Jin
authors.initials: YJ
authors.lastname: Lee
authors.affiliation: Department of Cancer Control and Policy, Graduate School of Cancer Science and Policy, National Cancer Center, Goyang, Republic of Korea jslee@ncc.re.kr.|National Cancer Center Research Institute & Hospital, National Cancer Center, Goyang, Republic of Korea.
authors.forename: Jin Soo
authors.initials: JS
authors.lastname: Lee
mesh_terms: D002277:Carcinoma / Q000453:epidemiology / Q000473:pathology; D005260:Female; D006306:Health Surveys; D006801:Humans; D015994:Incidence; D008207:Lymphatic Metastasis; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D012042:Registries; D056910:Republic of Korea / Q000453:epidemiology; D012189:Retrospective Studies; D013964:Thyroid Neoplasms / Q000453:epidemiology* / Q000473:pathology