An increase in the detection of small tumors, most likely a result of overdetection and unnecessary ultrasound examinations, may be responsible for a nationwide epidemic of thyroid cancer. A review of medical records of nationally representative samples of patients with a diagnosis of thyroid cancer in 1999, 2005, and 2008 was conducted and sample cases were randomly selected. 5,796 patients with thyroid cancer were included (n=891 in 1999; n=2,355 in 2005; n=2,550 in 2008). Researchers found:
- Between 1999 and 2008, the incidence of thyroid cancer increased 6.4-fold from 6.4 per 100,000 population to 40.7 per 100,000.
- 94.4% were for tumors <20 mm, which were detected mainly by screening.
- 97.1% of the total increase was localized and regional tumors.
- 99.9% of the increased incidences of clinically detected cases over the same period were tumors <20 mm.
Park S, Oh CM, Cho H, et al. Association between screening and the thyroid cancer “epidemic” in South Korea. [Published online ahead of print November 30, 2016]. BMJ. doi:10.1136/bmj.i5745.
In case anyone has questioned the importance of carefully thought out, evidence-based approaches to screening, the increased incidence of thyroid cancer in South Korea is an example of how screening can lead to expensive and potentially harmful over-diagnosis. The 6-fold increase in thyroid cancer in South Korea correlates with the increased use in that country of ultrasound as a screening method to detect thyroid cancers over the same period of time.1 The current study suggests that the cancers found were primarily very small cancers with no likely clinical significance, except that when they are evaluated and treated, they expose patients to the expense and side-effects of unnecessary treatment with no improvement in outcomes. Screening is always a careful balance of benefit vs harm, and the history of thyroid cancer screening with ultrasound is a lesson in the importance of ordering screening tests only when there is good evidence showing benefit. —Neil Skolnik, MD
- Ahn HS, Kim HJ, Welch HG. Korea’s thyroid-cancer “epidemic”— screening and overdiagnosis. N Engl J Med. 2014;371:1765-7. doi:10.1056/NEJMp1409841.
This Week's Must Reads
AHA Statement: Accurate Measurement of BP, Hypertension; ePub 2019 Mar 4; Muntner, et al
Coffee Consumption & Plasma Biomarkers, Am J Clin Nutr; ePub 2019 Mar 5; Hang, et al
Is Adding Aspirin to Warfarin Therapy Beneficial? , JAMA Intern Med; ePub 2019 Mar 4; Schaefer, et al
Urinary Oxalate Excretion & Risk of CKD Progression, JAMA Intern Med; ePub 2019 Mar 4; Waikar, et al
Psychosocial Stress & CV Health in Older Women, Circulation; ePub 2019 Feb 28; Burroughs-Peña, et al
Must Reads in Oncology
Do Vitamin D Supplements Prevent Cancer, CVD?, N Engl J Med; 2019 Jan 3; Manson, Cook, et al
Nonadherence to Cancer Screenings & Related Mortality, JAMA Intern Med; ePub 2018 Dec 28; Pierre-Victor, et al
Does Vitamin D Reduce Cancer & CVD Risk?, N Engl J Med; ePub 2018 Nov 10; Manson, et al
Interventions to Increase CRC Screening Rates, JAMA Intern Med; ePub 2018 Oct 15; Dougherty, et al
Smoking & Lung Cancer Mortality in the US to 2065, Ann Intern Med; ePub 2018 Oct 9; Jeon, et al