Why is thyroid cancer on the rise?

 
Between 1992 and 2012, the incidence of thyroid cancer more than doubled, from a little under 6 up to 13.5 people in 100,000. While it is one of the less lethal cancers (five-year survival rate is 97.9%), the fact that it’s becoming so prevalent so fast is generally seen as concerning. So what gives? Why is thyroid cancer on the rise?
At this point, we have one pretty good guess. Many diseases and conditions have suddenly spiked in diagnoses in the past, but not always because more cases were developing. Rather, new diagnostic criteria, increased awareness, or better technology change how these disorders have been found and assessed—meaning the number of diagnoses increases because those who were undiagnosed before have been recognized.
For example, changes in the DSM, the book used to diagnose mental illnesses and disorders in America, is thought to have played a strong role in the uptick of autism diagnoses. A January study of 677,915 Danish children over several decades found a similar trend when Danish autism criteria were broadened.
Technological advances may be to blame
In thyroid cancer’s case, technology advances may be to blame. Thanks to ultrasound and fine-needle biopsies and to accidental discoveries while investigating other issues, thousands more cases of thyroid cancer have been diagnosed. In these cases, many of these little benign tumors—known as nodules—never develop into full-blown cancer, and in fact are fairly harmless.
Previously, these people often would remain undiagnosed and unbothered for the course of their lives. Now, they’re being found—leading to the sharp rise in thyroid cancer, but keeping the level of deaths insignificantly changed.
“These cases have been there all along,” Dr. Louise Davies, assistant professor of surgery in the division of otolaryngology, head, and neck surgery at Dartmouth Medical School, told the New York Times. “We just didn’t see them until now. Understanding this requires that you think about the word ‘cancer’ in a different way than we usually do. You can have increased rates of incidence without changing the number of people who die.”
However, many groups (like the National Cancer Institute) and experts do not believe that this is the whole picture: “I think it is an oversimplification to say the increase in diagnosis is from the overuse of technology and only relates to small tumors that are insignificant,” Dr. Steven Sherman, medical director of the endocrine center at the University of Texas M.D. Anderson Cancer Center in Houston, told the Times.
But as to what this other cause is, no one knows or even seems to have a legitimate idea. The thyroid—a butterfly-shaped gland in the neck that makes hormones that help control heart rate, blood pressure, body temperature, and weight—often develops cancer upon exposure to radiation. Family history and chronic goiter can lead to it as well, but so far nothing has conclusively linked any of these factors to the sudden surge in diagnoses.
So, in a way, thyroid cancer is like the Lost Colony of Roanoke: It might be explained, it might not be, but for now we don’t really know.
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