CALGARY -- A study by researchers at the University of Calgary suggests there's an overdiagnosis epidemic when it comes to thyroid cancer.
Dawnelle Topstad and James Dickinson pored over four decades worth of Canadian data on the disease.
They found thyroid cancer incidence rates in Canada increased by almost six times in women and five times in men between 1970 and 2012.
There was a big spike after the early 1990s and the sharpest increase was in women between 40 and 60.
At the same time, the rates of people who died from the disease were low throughout the period, with little variation between men and women.
The researchers say there are likely to be consistently small numbers of lethal thyroid cancer cases, but many tumours detected don't progress or progress too slowly to pose much of a risk.
"The likely cause of the increase in incidence is an overdiagnosis epidemic for clinically unimportant lesions detected by modern diagnostic imaging," Topstad and Dickinson wrote.
They say further effort should focus on reducing overuse of diagnostic imaging and finding better ways of distinguishing between aggressive and low-risk tumours.
The study was published in CMAJ Open.
