While the incidence of thyroid cancer has nearly tripled since 1975, mortality rates have remained stable, suggesting that there is an epidemic of diagnosis rather than an epidemic of disease.
That's according to research published online in JAMA Otolaryngology -- Head and Neck Surgery (February 20, 2014).
Nearly the entire increase is due to a growing number of diagnoses for small papillary thyroid cancer, which is a common and less aggressive form of the disease and can be present in patients without symptoms, according to study authors Dr. Louise Davies of the Veterans Affairs Medical Center in White River Junction, VT, and Dr. H. Gilbert Welch of the Dartmouth Institute for Health Policy and Clinical Practice in Hanover, NH. The team also found that the increase in thyroid cancer was four times greater in women than in men.
The researchers used the Surveillance, Epidemiology, and End Results (SEER) program to analyze data for patients diagnosed with thyroid cancer from 1975 to 2009 in nine areas of the U.S.: Atlanta, Connecticut, Detroit, Hawaii, Iowa, New Mexico, Utah, the San Francisco-Oakland area in California, and the Seattle-Puget Sound area of Washington.
They found that the incidence of thyroid cancer has increased from 4.9 cases to 14.3 cases per 100,000 people to from 1975 to 2009. Virtually the entire increase was due to papillary thyroid cancer, which grew from 3.4 cases to 12.5 cases per 100,000 people during the study period.
Notably, the absolute increase in thyroid cancer among women (6.5 cases to 21.4 cases per 100,000 women) was almost four times more than the increase for men (3.1 cases to 6.9 cases per 100,000 men).
"The [overdiagnosis] problem is particularly acute for women, who have lower autopsy prevalence of thyroid cancer than men but higher cancer detection rates by a 3:1 ratio," the authors wrote.
Over the study period, the thyroid cancer mortality rate remained stable at about 0.5 deaths per 100,000 people, according to the researchers.
