Thyroid cancer rates tripled since 1975: What's driving the diagnoses?

Thyroid cancer rates have tripled since the 1970s, but researchers say it shouldn’t be a cause for alarm that more people are getting the disease.

Instead, they call the surging rates an “epidemic of diagnosis." While the number of people who have it has gone up, more people are not dying from the disease.

"We found that there is an ongoing epidemic of thyroid cancer in the United States. It does not seem to be an epidemic of disease, however," wrote the study's authors. "Instead, it seems to be substantially an epidemic of diagnosis: thyroid cancer incidence has nearly tripled since 1975, while its mortality has remained stable."

About 60,000 people were diagnosed with thyroid cancer in 2013, and 1,850 people died from the disease, according to National Cancer Institute estimates.

Thy thyroid is a two-lobed, butterfly-shaped gland below the Adam’s apple that produces hormones that regulate bodily functions including heart rate, blood pressure, body temperature and weight, according to the Mayo Clinic.

Symptoms may include a lump you can feel through the skin of your neck, changes to voice (increasing hoarseness), trouble swallowing, pain in your neck and throat and swollen lymph nodes.

The five-year survival rate for people diagnosed with stage I or II thyroid cancer is approaching 100 percent, according to the American Cancer Society.

Researchers looked at a nationally-representative sample of patients diagnosed with thyroid cancer between 1975 and 2009, who lived in nine areas of the country: 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 in 1975, 4.9 out of every 100,000 people were diagnosed with thyroid cancer, but by 2009, that rate climbed to 14.3 per 100,000.

The increase was almost entirely driven by diagnoses of papillary thyroid cancer, a type of cancer that develops in only one lobe of the thyroid gland that tends to grow very slowly and often spreads to the neck’s lymph nodes, the American Cancer Society notes. They account for approximately 8 out of 10 thyroid cancer diagnoses.

Overall, thyroid cancer rates rose four times higher for women than men. In 1975, 6.5 per 100,000 women were diagnosed. That grew to 21.4 per 100,000 by 2009. In men, the rates climbed from 3.1 per 100,000 to 3.8 per 100,000. It is unknown why women are more likely to develop the cancer than men.

The number of deaths from the disease has remained stable since 1975 at about 0.5 deaths for every 100,000 people diagnosed.

The researchers speculate that people are being “overdiagnosed” with papillary thyroid cancer despite not showing symptoms or having cancers that may never even cause harm. It may be driven by better diagnostic methods such as CT scans and ultrasound.

The researchers called on doctors to help their patients make better decisions on treatment by explaining to them that some of these cancers will never grow or cause harm -- even though it’s impossible to know which ones will be worrisome based on the available diagnostic techniques.

For example, they may want to wait to get treatment and monitor the cancer, what’s called active surveillance.

The study was published Feb. 20 in JAMA Otolaryngology -- Head and Neck Surgery.

Dr. Raymon Grogan, a surgeon at the University of Chicago Medicine who specializes in thyroid gland diseases, told Medscape that overdiagnosis through better detection was only part of the story. Rates are increasing elsewhere in the world where medical imaging is less common. He also disagreed with the active surveillance approach following a diagnosis.

"We don't know who will have a bad cancer," he said. "If papillary thyroid cancer is diagnosed, we can't just let it sit there."