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Association between screening and the thyroid cancer “epidemic” in South Korea: evidence from a nationwide study

BMJ 2016; 355 doi: https://doi.org/10.1136/bmj.i5745 (Published 30 November 2016) Cite this as: BMJ 2016;355:i5745
  1. Sohee Park, associate professor1 2,
  2. Chang-Mo Oh, associate scientist1,
  3. Hyunsoon Cho, assistant professor1 3,
  4. Joo Young Lee, postdoctoral fellow1 4,
  5. Kyu-Won Jung, senior scientist1,
  6. Jae Kwan Jun, chief scientist1 3,
  7. Young-Joo Won, senior scientist1 3,
  8. Hyun-Joo Kong, data manager1,
  9. Kui Son Choi, professor1 3,
  10. You Jin Lee, associate scientist5,
  11. Jin Soo Lee, chief scientist3 6
  1. 1National Cancer Control Institute, National Cancer Center, Goyang, Republic of Korea
  2. 2Department of Biostatistics, Yonsei University Graduate School of Public Health, Seoul, Republic of Korea
  3. 3Department of Cancer Control and Policy, Graduate School of Cancer Science and Policy, National Cancer Center, Goyang, Republic of Korea
  4. 4Department of Preventive medicine, Yonsei University, College of Medicine, Seoul, Republic of Korea
  5. 5Center for Thyroid Cancer, National Cancer Center, Goyang, Republic of Korea
  6. 6National Cancer Center Research Institute & Hospital, National Cancer Center, Goyang, Republic of Korea
  1. Correspondence to: J S Lee, National Cancer Center Research Institute & Hospital, National Cancer Center, 111, Jungbalsan-ro, Ilsandong-gu, Goyang, Gyeonggi-do 410-769, Republic of Korea jslee{at}ncc.re.kr
  • Accepted 21 October 2016

Abstract

Objective To investigate whether screening for thyroid cancer led to the current “epidemic” in South Korea.

Design Review of the medical records of nationally representative samples of patients with a diagnosis of thyroid cancer in 1999, 2005, and 2008.

Setting Sample cases were randomly selected from South Korea’s nationwide cancer registry, using a systematic sampling method after stratification by region.

Participants 5796 patients with thyroid cancer were included (891 in 1999, 2355 in 2005, and 2550 in 2008).

Main outcome measures 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.

Conclusion 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.

Footnotes

  • We thank the hospital staff and colleagues who collected patient information for the NEST study.

  • Contributors: SP and C-MO contributed equally to this study, and are joint first authors. All authors contributed to the data analysis and interpretation of the results, and reviewed and approved the final manuscript. JSL, the guarantor, had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. SP coordinated the study and wrote the manuscript. C-MO analysed the data and wrote the manuscript. SP, Y-JW, H-JK, and Y-JL collected and interpreted the data. HC, K-WJ, Y-JW, J-KJ, H-JK, K-SC, Y-JL, and JSL contributed to the discussion and reviewed and edited the manuscript.

  • Funding: This work was supported by a grant from the National Cancer Center (NCC-1310223 and NCC-1032020). The views expressed in this article are those of the authors and do not necessarily represent the views of the NCC, Goyang, Korea. The NEST survey was conducted with funding support from the NCC (NCC-1032020). The funders had no role in coordinating the study or writing the manuscript.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; and no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: This research protocol was approved by the National Cancer Center institutional review board (NCC2015-0152).

  • Data sharing: The dataset for the NEST study is available on request (http://kccrsurvey.cancer.go.kr/index.do). Informed consent was not obtained, but the presented data are anonymised and the risk of identification is low.

  • Transparency: The lead author (JSL) affirms that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies with the study as planned (and, if relevant, registered) have been explained.

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