Hyeong Sik Ahn of Korea University, writing with Gilbert Welch of Dartmouth, compared that surge in diagnoses to the actual death rate from thyroid cancer over the same period and found the death rate had barely moved.
The authors traced the surge to the spread of cheap, widely available thyroid ultrasound, often added on to routine checkups with no symptoms prompting it. Virtually all of the newly found tumors were small papillary thyroid cancers, a slow-growing type that in most cases would never have caused symptoms or death if left undetected for a person's whole life.
The pattern is a textbook case of overdiagnosis, finding disease that technically meets a diagnostic definition but would never have caused harm, followed by surgery and lifelong thyroid medication for people who did not need either. Thyroid surgeries in South Korea fell by about a third after a 2014 public debate over routine screening, though overdiagnosis from incidental imaging remains a broader problem.
Read the original study
More screening found cancer that was not a threat.
Source
- Ahn, H. S., Kim, H. J., & Welch, H. G. (2014). Korea's Thyroid-Cancer “Epidemic” — Screening and Overdiagnosis. New England Journal of Medicine, 371(19), 1765–1767. https://doi.org/10.1056/nejmp1409841