Why Are Thyroid Cancer Cases on the Rise?

While thyroid cancer is surging, the reasons why are very much a matter of debate. Some researchers claim the numbers primarily reflect improved diagnostic and detection techniques, others say the problem goes deeper.

thyroid cancer
(L-R) Drs. Jochen Lorch, Francis Moore and Erik Alexander, leaders of Dana-Farber’s Thyroid Center.

Official statistics depict a disease on the rise. Data collected by the National Cancer Institute (NCI) show the incidence of thyroid cancer – the number of people diagnosed within a given-size population – has more than doubled since the early 1970s. For women, it is the fastest-growing cancer as measured by the number of new cases each year.

Many investigators point to improved methods of detection as the major force behind the increase. Over the past 35 years, the use of ultrasound and fine-needle biopsies has enabled doctors to diagnose thousands of cases that might have been missed in the past. A study published in 2006 concluded that a 140 percent increase in thyroid cancer diagnoses between 1973 and 2002 was largely a result of “increased diagnostic scrutiny.”

If the incidence of thyroid cancer were actually rising, researchers say, detection of thyroid tumors of all sizes would have increased. What researchers found, instead, was that 87 percent of the increase was in small papillary thyroid tumors that were less than two centimeters in diameter. Many of these growths, researchers say, would never have posed a danger to patients’ health, even if they hadn’t been detected.

Still, some researchers argue that view is oversimplistic. Because doctors often can’t predict which growths are likely to be harmful and which aren’t, early detection of any thyroid abnormality is important for proper treatment, they say.

A study published last year attributes much of the increase in thyroid cancer incidence to overdiagnosis. Using NCI data, the investigators found that the incidence rose from 4.9 people per 100,000 in 1975 to 14.3 per 100,000 in 2009 – a nearly 300% jump. When they looked at the percentage of patients who died of the disease over that period, however, they found it remained stable. If doctors were detecting more dangerous cases of thyroid cancer – rather than merely diagnosing more small, innocuous growths – the mortality rate would be expected to climb along with the incidence. Because that didn’t happen, the investigators concluded that the figures indicate an “epidemic of diagnosis” rather than disease.

As with the 2006 study, however, some researchers have taken issue with these findings. They argue that the mortality rate appears flat mainly because it was charted over a relatively long time – 35 years. Had it covered just the last 10 years, critics say, it would show that the death rate from thyroid disease is increasing faster than any other cancer except liver cancer.

“The tricky part is, how do we identify patients with disease that is not going to cause problems over a long period of time or perhaps ever, and how do we find patients who need to undergo aggressive treatment right away because of the nature of their disease?” says Jochen Lorch, MD, director of the Thyroid Cancer Center at Dana-Farber. “As we learn more about what drives thyroid cancer on a molecular level, we will have answers to that question in the future, but this will take a bit more work to figure out.”

6 thoughts on “Why Are Thyroid Cancer Cases on the Rise?”

  1. I find this research both fascinating and relevant. I was diagnosed with metastatic papillary carcinoma and am 2+ years out from TT and RAI and 9 mos out from central neck dissection to remove lymph nodes and extra nodal extension and I’m BRAF V600 positive.

    I read everything and keep up with studies, trials, and guidelines. I have email and in-person discussion with my physicians at Johns Hopkins about this stuff and plan on absorbing as much as I can at the ThyCa conference in October.

    As I say, research anywhere benefits cancer patients everywhere. I’m an advocate for education and good doctor/patient relationships. All this helps. Thanks!

  2. I think one problem is the metastases of cancer. After aggressive treatment the condition of some patients will under control, but some will die of metastases. Recently, a research found that 21 DNA hypermethylation is related to the cancer metastases by whole-genome bisulfite sequencing(WGBS). This provides foundation for finding who needs additional treatment.

    • Wow. So does this mean we can test for a specific gene to predict weather or not cancer will become metstatic? If so, it seems like this should be part of every cancer diagnosis and treatment plan.

  3. Could there be a connection to the melt down and melt out of the reactors in Japan ? Iodine 131 was released in large quantities, and still leaks out to this very day. I 131 has been proven to cause thyroid health issues.

  4. I am a 6+ year survivor after having thyroidectomy for papillary and follicular cancer. I have two questions: 1. If my cancer was listed on the path report as “invasive”, which I assume means it had broken out of the protective capsule, is it more likely to reoccur that if it had been contained? My doc is noncommital on this issue. 2. In recent literature, I read that those receiving more than 150 millicures of RAI are more likely to have other serious cancers later. I had 150 millicures. What is your take on this?

  5. Dear Temme —

    Thank you for your question and for reading Insight. Unfortunately, we cannot give out medical advice on this blog or over email. If you are interested in a second opinion at Dana-Farber, the procedure is the same as for becoming a new patient. If you are able to come to Boston to meet with our treatment team, please call 877-442-DFCI (877-442-3324) or fill out this online appointment request form:


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    Wishing you all the best.

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