Thyroid cancer incidence has tripled since the 1970s. Most of the increase is attributed to the introduction of diagnostic ultrasound and fine-needle aspiration biopsies. Use of these two procedures escalated once ultrasound machines, initially found only at hospitals, became increasingly available in doctors’ offices. Autopsy studies show cancer is present in the thyroids of most people who died from other causes. Consequently, some researchers suspect that diagnosing thyroid cancer at the earliest stage is causing much more harm than good.

This suspicion was confirmed in a new study that found people with papillary thyroid cancer (the most common type) have an excellent prognosis whether or not they are treated within the first year of diagnosis. And they have an excellent prognosis whether part or all of the thyroid gland is surgically removed. Those who receive the latter treatment must go on thyroid replacement therapy for the rest of their lives.

These conclusions are based on 20-year data collected from 17 cancer registries maintained by the U.S. National Cancer Institute. Of particular interest were the people diagnosed with papillary thyroid cancer that had not progressed beyond the thyroid gland. More than 35,600 thyroid cancer patients, diagnosed between 1973 and 2005, fit this description. The researchers specifically wanted to know what happened to the people whose tumors were not treated for a year or more after diagnosis.

Here’s the bottom line: At six years, less than half a percent of those treated within a year of diagnosis had died. The death rate of the people who did not receive immediate treatment was also low (1.2%). As for those followed for 20 years: 99% of immediate-treatment group and 97% of the no-immediate treatment group were alive at 20 years. In other words, early diagnosis and immediate treatment accounted for a 2% difference.

This study was conducted by Louise Davies, MD, and H. Gilbert Welch, MD, of the Dartmouth Institute for Health Policy and Clinical Practice, and published last month in Archives of Otolaryngology, Head and Neck Surgery. It’s a sequel to their 2006 landmark study that identified ultrasound and fine-needle biopsies as the major reasons for the increase in thyroid cancer incidence. The new study was funded in part by a Research Enhancement Award from the U.S. Department of Veterans Affairs.

Davies and Welch caution doctors that the “outcomes” of patients treated for papillary thyroid cancer “are extremely favorable,” but the risks of treatment must also be taken into account. “Survival is so good that it is appropriate to consider whether the risks of complications outweigh the benefits of treatment during discussions about when and how to treat the disease. The risk of permanent hypoparathyroidism and significant damage to laryngeal function have been reported to range from 3% to 5%…”

In the editorial that accompanied this study, a counter argument was offered by Erich M. Sturgis, MD, and Steven I. Sherman, MD, of the M.D. Anderson Cancer Center, Houston. They agreed that a “wait and see” approach may be appropriate for many patients, particularly those with additional, more serious medical conditions. On the other hand, a person with a large tumor and a history of radiation exposure should be treated immediately. Furthermore, Sturgis and Sherman say that they see many patients with recurrent thyroid cancer “after an inadequate initial evaluation and/or treatment.”

And as for that 2% difference in the 20-year survival rate between the patients who were treated immediately and those who were not. Sturgis and Sherman extrapolate that 2% to the estimated 35,000 Americans diagnosed yearly with papillary thyroid cancer. It might be a tiny statistic, they say, but it represents about 500 to 700 people who will die of papillary thyroid cancer. “Certainly, most of these hypothetical 500 to 700 people would have wished their physicians had offered them the treatment that had ‘statistically’ better survival (i.e., surgery).”

Still, the editorialists do not dismiss the overtreatment concerns of Davies and Welch. “… occult papillary thyroid cancers “might even represent the normal aging process of the thyroid gland.” Davies and Welch are quoted approvingly:

“Because so many of these cancers would likely never have caused symptoms during life, epidemiologists have labeled the phenomenon, ‘overdiagnosis.’ Overdiagnosis is a cause for concern because it makes it hard to identify which patients need treatment…Further studies will be needed to determine if a more cautious diagnostic approach—perhaps simply providing follow-up for symptomatic thyroid nodules—is worthwhile. In addition, papillary cancers smaller than 1 cm could be classified as a normal finding.”

For more information
Read this 2006 article about Davies and Welch initial paper on the rise in thyroid cancer incidence. See the suggestions from Dr. Davies about finding a second opinion, including a second opinion about undergoing an ultrasound of the thyroid in the first place. (Click here for “Cancers that do not kill”)

The thyroid cancer incidence has been rising for three decades, and most Americans are treated immediately. Yet there’s no change in U.S. thyroid cancer death rate, which has always been very low. Click here for the National Cancer Institute’s take on this point.

Maryann Napoli, Center for Medical Consumers©

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