Thyroid Cancer Diagnoses on the Rise

In the United States, thyroid cancer is only preceded by melanoma and cancers of the kidney and renal pelvis on the list of cancers mounting in incidence. The disease’s frequency has tripled since 1973, and it’s increasing by more than 6 percent annually. However, experts wonder if that increase is real or if better diagnostics are the cause — especially since countries that report similar growth are all developed nations.

Papillary thyroid tumors, commonly referred to as “incidentalomas,” are usually discovered during work-up for other medical problems, though many experts believe thyroid incidentalomas are typically subclinical, meaning that they wouldn’t cause an adverse outcome during a patient’s lifetime if they were left alone.

In light of that, a group of researchers set out to determine if thyroid cancer is now an over-diagnosed condition. To be considered over-diagnosed, a disease must meet two criteria: A large reservoir of occult disease and an increasing demand for healthcare interventions to detect it. The large reservoir of occult thyroid cancer is clear, as pathologists have found undiagnosed thyroid cancer in up to 35 percent of autopsies; therefore, the researchers focused on the second marker of over-diagnosis for their study published in Thyroid.

Using the US Surveillance, Epidemiology, and End Results (SEER) Program — a cancer statistics database that covers roughly 28 percent of the US population — the authors found:

• Papillary thyroid cancer incidence tends to be highest in counties with higher income levels and larger proportions of white-collar residents and people holding Bachelor’s degrees.
• Incidence rates tend to be the lowest in counties with higher proportions of unemployed, uninsured, nonwhite, non-English speaking, low-income, and lesser educated residents.
• Access to healthcare and the incidence of papillary thyroid cancer appear directly related.

The researchers concluded that based on autopsy results, between 25 million and 100 million Americans have undiagnosed papillary thyroid cancer —a condition that may not cause symptoms or death if left untreated. Considering the large subclinical reservoir and the association between healthcare access and diagnosis, the authors concluded that papillary thyroid cancer is currently over-diagnosed.