Thyroid cancer on the rise, mortality rate remains low

BOSTON — Thyroid cancer incidence has dramatically increased and at the American Thyroid Association Cancer Frontiers in Thyroid Cancer meeting Ernest L. Mazzaferri, MD, questioned whether the rise is related to more true cases of cancer or ascertainment bias.

Thyroid cancer has increased 2.4-fold in the past two decades. However, previously published data show a flat mortality rate of 0.5 per 100,000 (JAMA. 2008;295:2164-2167).

“A flat mortality rate does not completely reflect the clinical situation,” and fails to take into account subsets of patients, said Mazzaferri, professor emeritus of medicine and physiology, Ohio State University.

“The real issue is that thyroid cancer is a major undiagnosed problem in men and may be due to ascertainment bias from more screenings in women,” such as the wide use of neck ultrasonography, he said.

The National Cancer Institute and American Cancer Society estimated that there were 37,340 new cases of thyroid cancer and 1,590 cases of cancer-related mortality in the United States in 2008 so far. Additionally, estimates suggest a prevalence of thyroid cancer in 388,386 people.

Mazzaferri also discussed another changing demographic in thyroid cancer that has affected management: type of cancer. Particularly, incidence of low-risk thyroid cancers, which again may be due to more screening and ultrasonography, he said. Papillary thyroid cancer incidence increased 2.9-fold from 1979 to 2002 and is the most common type of thyroid cancer (80%), according to other data.

“Thyroid cancer is a very complex problem — not an open and shut case,” he said. – by Katie Kalvaitis

The real question is whether the increase in thyroid cancer incidence is a biological phenomenon or ascertainment bias. [According to previous data] 67% of people have thyroid nodules, and yet only 35,000 people have thyroid cancer. Just think about it — there are 300 million people in the United States, 150 million are adults and 75 million of them have a thyroid nodule yet just 33,000 have thyroid cancer. That is one-thousandth of all people. There is lots of thyroid cancer out there, we are just finding it more now. Sometimes, half of the patients I see in a day are there because they had a nodule detected by accident by some other imaging technique.

– David S. Cooper, MD

Director, Division of Endocrinology, Sinai Hospital of Baltimore

For more information:
Mazzaferri EL. Changing demographics in thyroid cancer: impact on management. Presented at: American Thyroid Association Frontiers in Thyroid Cancer; July 11-12, 2008; Boston.